From 13732b15d8a2f7b4197184d5012dcb16629bab06 Mon Sep 17 00:00:00 2001 From: Charles Haley Date: Sun, 28 Feb 2021 16:13:55 +0000 Subject: [PATCH] Rewrite much of the template language manual document. The commit on 27 Feb isn't good. The manual page should be regenerated from this commit. --- manual/template_lang.rst | 830 +++++++++++++-------------------------- 1 file changed, 268 insertions(+), 562 deletions(-) diff --git a/manual/template_lang.rst b/manual/template_lang.rst index 5c3d1132d6..5d5b0519a2 100644 --- a/manual/template_lang.rst +++ b/manual/template_lang.rst @@ -3,17 +3,16 @@ The calibre template language ======================================================= -The calibre template language is used in various places. It is used to control the folder structure and file name -when saving files from the calibre library to the disk or e-book reader. It is also used to define "virtual" -columns that contain data from other columns and so on. +The calibre template language is a calibre-specific programming language used throughout calibre. For example, it is used to specify the folder structure and file name when saving files from the calibre library to the disk or e-book reader, define 'rules' for adding icons to the calibre book list, and to define "virtual" columns that contain data from other columns. The language is built around the notion of a 'template'; a template specifies which book metadata to use and how it is to be formatted. -The basic template language is simple but has powerful advanced features. A template consists of text -and names in curly brackets that are then replaced by the corresponding metadata from the book being -processed. For example, the default template used for saving books to device in calibre is:: +Basic Templates +--------------- + +A basic template consists one or more 'template expressions'. A template expression consists of text and names in curly brackets that are then replaced by the corresponding metadata from the book being processed. For example, the default template used for saving books to device in calibre is:: {author_sort}/{title}/{title} - {authors} -For the book "The Foundation" by "Isaac Asimov" it will become:: +For the book "The Foundation" by "Isaac Asimov" the will become:: Asimov, Isaac/The Foundation/The Foundation - Isaac Asimov @@ -21,273 +20,168 @@ The slashes are text, which is put into the template where it appears. For examp {author_sort} Some Important Text {title}/{title} - {authors} -For the book "The Foundation" by "Isaac Asimov" it will become:: +For the book "The Foundation" by "Isaac Asimov" the template produces:: Asimov, Isaac Some Important Text The Foundation/The Foundation - Isaac Asimov -You can use all the metadata fields available in calibre in a template, including any custom columns -you have created, by using its 'lookup name'. To find the lookup name for a column (field) hover your -mouse over the column header. Names for custom columns (columns you have created yourself) always have -a # as the first character. For series type custom columns there is always an additional field -named ``#seriesname_index`` that is the series index for that series. So if you have a custom -series field named ``#myseries``, there will also be a field named ``#myseries_index``. +A template can access all the metadata available in calibre, including custom columns (columns you create yourself), by using its ``lookup name``. To find the lookup name for a column (sometimes called a 'field'), hover your mouse over the column header in calibre's book list. Lookup names for custom columns always have a ``#`` as the first character. For series type columns there is an additional field named ``'#lookup name'_index`` that is the series index for that series. So if you have a custom series field named ``#myseries``, there will also be a field named ``#myseries_index``. The standard series column's index is named ``series_index``. In addition to the column based fields, you also can use:: {formats} - A list of formats available in the calibre library for a book {identifiers:select(isbn)} - The ISBN of the book -If a book does not have a particular piece of metadata, the field in the template is replaced by the -empty string (``''``) for that book. Consider, for example:: +If a book does not have a particular piece of metadata, the field in the template is replaced by the empty string (``''``). Consider, for example:: {author_sort}/{series}/{title} {series_index} -If a book has a series, the template will produce:: +If a book has a series, the template produces:: Asimov, Isaac/Foundation/Second Foundation 3 -and if a book does not have a series:: +and if the book does not have a series:: Asimov, Isaac/Second Foundation -(calibre automatically removes multiple slashes and leading or trailing spaces). +The template processor automatically removes multiple slashes and leading or trailing spaces. Advanced formatting ---------------------- -You can do more than just simple substitution with the templates. You can also conditionally include -text and control how the substituted data is formatted. +You can do more than simple substitution with the templates. You can also conditionally include additional text and control how substituted data is formatted. -First, conditionally including text. There are cases where you might want to have text appear -in the output only if a field is not empty. A common case is ``series`` and ``series_index``, where -you want either nothing or the two values with a hyphen between them. calibre handles this case -using a special field syntax. +**Conditionally including text** + +Sometimes you want to have text appear in the output only if a field is not empty. A common case is ``series`` and ``series_index``, where you want either nothing or the two values with a hyphen between them. calibre handles this case using a special template item syntax. For example, assume you want to use the template:: {series} - {series_index} - {title} -If the book has no series, the answer will be ``- - title``. Most people would rather the result -be simply ``title``, without the hyphens. To do this, use the extended syntax ``{field:|prefix_text|suffix_text}``. -When you use this syntax, if field has the value SERIES then the result will be ``prefix_textSERIESsuffix_text``. -If field has no value, then the result will be the empty string (nothing); the prefix and suffix are ignored. -The prefix and suffix can contain blanks. +If the book has no series, the answer will be ``- - title``, which is probably not what is wished. Most people would prefer the result be ``title``, without the hyphens. To do this, use the extended template syntax:: + + {field:|prefix_text|suffix_text} + +When you use this syntax, if ``field`` has the value ``SERIES`` then the result will be ``prefix_textSERIESsuffix_text``. If ``field`` has no value, then the result will be the empty string (nothing) because the prefix and suffix are ignored. The prefix and suffix can contain blanks. **Do not use subtemplates (`{ ... }`) or functions (see below) in the prefix or the suffix.** -Using this syntax, we can solve the above series problem with the template:: +Using this syntax, we can solve the above no-series problem with the template:: {series}{series_index:| - | - }{title} -The hyphens will be included only if the book has a series index, which it will have only if it has a series. +The hyphens will be included only if the book has a series index, which it has only if it has a series. -Notes: you must include the colon if you want to use a prefix or a suffix. You must either use -no \| characters or both of them; using one, as in ``{field:| - }``, is not allowed. It is OK not -to provide any text for one side or the other, such as in ``{series:|| - }``. Using ``{title:||}`` is -the same as using ``{title}``. +Notes:: + * You must include the colon after the lookup name if you want to use a prefix or a suffix. + * You must either use no \| characters or both of them; using one, as in ``{field:| - }``, is not allowed. + * It is OK not to provide text for either the prefix or the suffix, such as in ``{series:|| - }``. The template ``{title:||}`` is the same as ``{title}``. -Second: formatting. Suppose you wanted to ensure that the series_index is always formatted as three +**Formatting** + +Suppose you want to ensure that the series_index is always formatted as three digits with leading zeros. This does the trick:: {series_index:0>3s} - Three digits with leading zeros -If instead of leading zeros you want leading spaces, use:: - - {series_index:>3s} - Three digits with leading spaces - For trailing zeros, use:: {series_index:0<3s} - Three digits with trailing zeros -If you use series indices with sub values (e.g., 1.1), you might want to ensure that the decimal -points line up. For example, you might want the indices 1 and 2.5 to appear as 01.00 and 02.50 so -that they will sort correctly. To do this, use:: +If you use series indices with fractional values (e.g., 1.1), you might want the decimal points to line up. For example, you might want the indices 1 and 2.5 to appear as 01.00 and 02.50 so that they will sort correctly. To do this, use:: - {series_index:0>5.2f} - Five characters, consisting of two digits with leading zeros, a - decimal point, then 2 digits after the decimal point + {series_index:0>5.2f} - Five characters consisting of two digits with leading zeros, a decimal point, then 2 digits after the decimal point. If you want only the first two letters of the data, use:: {author_sort:.2} - Only the first two letter of the author sort name -The calibre template language comes from Python. For more details on the syntax of these advanced formatting -operations see the `Python documentation `_. +Much of the calibre template language comes from Python. For more details on the syntax of these advanced formatting operations see the `Python documentation `_. -Using templates in custom columns ----------------------------------- +Using templates to define custom columns +----------------------------------------- -Sometimes you want to display metadata in the book list that calibre does not normally display, or to -display data in a way different from how calibre normally does. For example, you might want to -display the ISBN, a field that calibre does not display. You can use custom columns for this by creating -a column with the type 'column built from other columns' (hereafter called composite columns), and -entering a template. Result: calibre will display a column showing the result of evaluating that -template. To display the ISBN, create the column and enter ``{identifiers:select(isbn)}`` into the -template box. To display a column containing the values of two series custom columns separated by a comma, -use ``{#series1:||,}{#series2}``. +Sometimes you want to display information that isn't in calibre metadata or differently from how calibre's normal format. For example, you might want to display the ISBN, a field that calibre does not display. You can solve this problem using custom columns creating a column with the type 'Column built from other columns' (hereafter called composite columns), and entering a template to generate what is to be displayed. A column will be created showing the result of evaluating the template. For example, to display the ISBN, create the column and enter ``{identifiers:select(isbn)}`` into the template box. To display a column containing the values of two series custom columns separated by a comma, use ``{#series1:||,}{#series2}``. Composite columns can use any template option, including formatting. You cannot edit the data displayed in a composite column. If you edit a composite column, for example -by double-clicking it, you will open the template for editing, not the underlying data. Editing the -template on the GUI is a quick way of testing and changing composite columns. +by double-clicking it, calibre will open the template for editing, not the underlying data. Editing the template on the GUI is a quick way of testing and changing composite columns. .. _single_mode: Using functions in templates - Single Function Mode --------------------------------------------------- -Suppose you want to display the value of a field in upper case, when that field is normally in title case. -You can do this (and many more things) using the functions available for templates. For example, to -display the title in upper case, use ``{title:uppercase()}``. To display it in title case, -use ``{title:titlecase()}``. +Suppose you want to display the value of a field in upper case, when that field is normally in title case. You can do this using the functions available for templates. For example, to display the title in upper case, use the ``uppercase`` function, as in ``{title:uppercase()}``. To display it in title case, use ``{title:titlecase()}``. -Functions are put in the format part, going after the ``:`` and before the first ``|`` or the closing ``}``. -If you have both a format and a function reference, the function comes after another ``:``. -Functions must always end with ``()``. Some functions take extra values (arguments), and these go inside the ``()``. +Functions are put in the format part of the template, going after the ``:`` and before the first ``|`` or the closing ``}`` if no prefix/suffix is used. If you have both a format and a function reference, the function comes after another ``:``. Functions return the value of the field used in the template, suitably modified. -Functions are always applied before format specifications. See further down for an example of using -both a format and a function, where this order is demonstrated. +The syntax for using functions is ``{lookup_name:function(arguments)}``, or ``{lookup_name:function(arguments)|prefix|suffix}``. Arguments are separated by commas. Literal commas (commas as arguments) must be preceded by a backslash ( ``\`` ). The last (or only) argument cannot contain a closing parenthesis ( ``)`` ). Function names must always end with ``()``. Some functions require extra values (arguments), and these go inside the ``()``. -The syntax for using functions is ``{field:function(arguments)}``, -or ``{field:function(arguments)|prefix|suffix}``. Arguments are separated by commas. Literal commas (commas as -arguments) must be preceded by a backslash ( ``\`` ). The last (or only) argument cannot contain a -closing parenthesis ( ``)`` ). Functions return the value of the field used in the template, -suitably modified. +Functions are evaluated before format specifications and the prefix/suffix. See further down for an example of using both a format and a function. -Important: If you have programming experience, please note that the syntax in this mode (single function) -is not what you might expect. Strings are not quoted. Spaces are significant. All arguments must be -constants; there is no sub-evaluation. +Important: If you have programming experience, please note that the syntax in this mode (Single Function Mode) is not what you expect. Strings are not quoted. Spaces are significant. All arguments must be constants; there is no sub-evaluation. -**Do not use subtemplates (`{ ... }`) as function arguments.** Instead, -use :ref:`Template Program Mode ` and :ref:`General Program Mode `. +**Do not use subtemplates (`{ ... }`) as function arguments.** Instead, use :ref:`Template Program Mode ` and :ref:`General Program Mode `. -Many functions use regular expressions. In all cases, regular expression matching is case-insensitive. +Some functions use regular expressions. In the template language regular expression matching is case-insensitive. -The functions available are listed below. Note that the definitive documentation for functions is -available in the section :ref:`Function reference `: +The functions intended for use in Single Function Mode are listed below. Note: the definitive documentation for functions is available in the section :ref:`Function reference `: + + * ``lowercase()`` -- returns the value of the field in lower case. + * ``uppercase()`` -- returns the value of the field in upper case. + * ``titlecase()`` -- returns the value of the field in title case. + * ``capitalize()`` -- returns the value with the first letter upper case and the rest lower case. + * ``contains(pattern, text if match, text if not match)`` -- checks if the field's value is matched by the regular expression ``pattern``. Returns ``text if match`` if if the pattern matches the value, otherwise it returns ``text if no match``. + * ``count(separator)`` -- interprets the value as a list of items separated by ``separator`` and returns the number of items in the list. Most lists use a comma as the separator, but ``authors`` uses an ampersand (&). Examples: ``{tags:count(,)}``, ``{authors:count(&)}``. Aliases: ``count()``, ``list_count()`` + * ``format_number(template)`` -- interprets the value as a number and formats that number using a Python formatting template such as ``"{0:5.2f}"`` or ``"{0:,d}"`` or ``"${0:5,.2f}"``. The formatting template must begin with ``{0:`` and end with ``}`` as in the above examples. Exception: you can leave off the leading "{0:" and trailing "}" if the format template contains only a format. See the template language and the `Python documentation `_ for more examples. Returns the empty string if formatting fails. + * ``human_readable()`` -- expects the value to be a number and returns a string representing that number in KB, MB, GB, etc. + * ``ifempty(text if empty)`` -- if the value is not empty then return the value of the field, otherwise return `text if empty`. + * ``in_list(separator, pattern, found_val, ..., not_found_val)`` -- interpret the value as a list of items separated by ``separator``, checking the ``pattern`` against each item in the list. If the ``pattern`` matches an item then return ``found_val``, otherwise return ``not_found_val``. The pair ``pattern`` and ``found_value`` can be repeated as many times as desired, permitting returning different values depending on the item value. The patterns are checked in order. The first match is returned. + * ``language_codes(lang_strings)`` -- return the `language codes `_ for the language names passed in `lang_strings`. The strings must be in the language of the current locale. ``Lang_strings`` is a comma-separated list. + * ``language_strings(lang_codes, localize)`` -- return the `language names `_ for the language codes passed in `lang_codes`. If `localize` is zero, return the strings in English. If ``localize`` is not zero, return the strings in the language of the current locale. ``Lang_codes`` is a comma-separated list. + * ``list_item(index, separator)`` -- interpret the value as a list of items separated by ``separator``, returning the `index`th item. The first item is number zero. The last item can be returned using an index of ``-1`` as in ``list_item(-1,separator)``. If the item is not in the list, then the empty string is returned. + * ``lookup(pattern, field, pattern, field, ..., else_field)`` -- like ``switch`` (below), except the ``field`` arguments are ``lookup names``, not text. The value of the field named by ``lookup key`` will be used. Note that because composite columns are fields, you can use this function in one composite column to use the value of some other composite column. + * ``rating_to_stars(use_half_stars)`` -- Returns the rating as string of star (``★``) characters. The value must be a number between 0 and 5. Set use_half_stars to 1 if you want half star characters for fractional numbers. + * ``re(pattern, replacement)`` -- return the field after applying the regular expression. All instances of `pattern` are replaced with `replacement`. The template language uses `Python regular expressions `_. + * ``select(key)`` -- interpret the value as a comma-separated list of items, with each item having the form ``id:value`` (``identifier`` format). The function finds the first pair with the id equal to key and returns the corresponding value. This function is particularly useful for extracting a value such as an ISBN from the set of identifiers for a book. + * ``shorten(left chars, middle text, right chars)`` -- Return a shortened version of the value, consisting of ``left chars`` characters from the beginning of the value, followed by ``middle text``, followed by ``right chars`` characters from the end of the value. ``Left chars`` and ``right chars`` must be postive integers. Example: assume you want to display the title in a field at most 15 characters in length. One template that does this is ``{title:shorten(9,-,5)}``. For a book with the title `Ancient English Laws in the Times of Ivanhoe` the result will be `Ancient E-nhoe`: the first 9 characters of the title, a ``-``, then the last 5 characters. If the value's length is less than ``left chars`` + ``right chars`` + the length of ``middle text`` then the value will be returned unchanged. For example, the title `The Dome` would not be changed. + * ``str_in_list(separator, string, found_val, ..., not_found_val)`` -- interpret the field as a list of items separated by ``separator``, comparing ``string`` against each value in the list. The ``string`` is not a regular expression. If ``string`` equals an item (ignoring case) then return ``found_val``, otherwise return ``not_found_val``. If ``string`` contains separators then it is also treated as a list and each subvalue is checked. The ``string`` and ``found_value`` pairs can be repeated as many times as desired, permitting returning different values depending on the search. If none of the strings match then ``not_found_value`` is returned. The strings are checked in order. The first match is returned. + * ``subitems(start_index, end_index)`` -- This function breaks apart lists of tag-like hierarchical items such as genres. It interprets the value as a comma-separated list of tag-like items, where each item is a period-separated list. It returns a new list made by extracting from each item the components from ``start_index`` to ``end_index``, then merging the results back together. Duplicates are removed. The first subitem in a period-separated list has an index of zero. If an index is negative then it counts from the end of the list. As a special case, an end_index of zero is assumed to be the length of the list. - * ``lowercase()`` -- return value of the field in lower case. - * ``uppercase()`` -- return the value of the field in upper case. - * ``titlecase()`` -- return the value of the field in title case. - * ``capitalize()`` -- return the value with the first letter upper case and the rest lower case. - * ``contains(pattern, text if match, text if not match)`` -- checks if field contains matches for the - regular expression `pattern`. Returns `text if match` if matches are found, otherwise it - returns `text if no match`. - * ``count(separator)`` -- interprets the value as a list of items separated by `separator`, returning - the number of items in the list. Most lists use a comma as the separator, but authors uses an ampersand. - Examples: `{tags:count(,)}`, `{authors:count(&)}`. - Aliases: ``count()``, ``list_count()`` - * ``format_number(template)`` -- interprets the field as a number and format that number using a - Python formatting template such as ``"{0:5.2f}"`` or ``"{0:,d}"`` or ``"${0:5,.2f}"``. The - field_name part of the template must be a 0 (zero) (the "{0:" in the above examples). - You can leave off the leading "{0:" and trailing "}" if the template contains only a format. See - the template language and Python documentation for more examples. Returns the empty string if - formatting fails. - * ``human_readable()`` -- expects the value to be a number and returns a string representing that - number in KB, MB, GB, etc. - * ``ifempty(text)`` -- if the field is not empty, return the value of the field. Otherwise return `text`. - * ``in_list(separator, pattern, found_val, ..., not_found_val)`` -- interpret the field as a list of - items separated by `separator`, evaluating the `pattern` against each value in the list. If - the `pattern` matches a value, return `found_val`, otherwise return `not_found_val`. The `pattern` and - `found_value` can be repeated as many times as desired, permitting returning different values - depending on the search. The patterns are checked in order. The first match is returned. - * ``language_codes(lang_strings)`` -- return the language codes for the strings passed in `lang_strings`. - The strings must be in the language of the current locale. `Lang_strings` is a comma-separated list. - * ``language_strings(lang_codes, localize)`` -- return the strings for the language codes passed - in `lang_codes`. If `localize` is zero, return the strings in English. If localize is not zero, - return the strings in the language of the current locale. `Lang_codes` is a comma-separated list. - * ``list_item(index, separator)`` -- interpret the field as a list of items separated by `separator`, - returning the `index`th item. The first item is number zero. The last item can be returned using - `list_item(-1,separator)`. If the item is not in the list, then the empty value is returned. The - separator has the same meaning as in the `count` function. - * ``lookup(pattern, field, pattern, field, ..., else_field)`` -- like switch, except the arguments - are field (metadata) names, not text. The value of the appropriate field will be fetched and used. - Note that because composite columns are fields, you can use this function in one composite field to - use the value of some other composite field. This is useful when constructing variable save paths - (more later). - * ``rating_to_stars(use_half_stars)`` -- Returns the rating as string of star characters. The source - value must be a number between 0 and 5. Set use_half_stars to 1 if you want half star characters - for custom ratings columns that are not integers, for example 2.5. - * ``re(pattern, replacement)`` -- return the field after applying the regular expression. All instances - of `pattern` are replaced with `replacement`. As in all of calibre, these are Python-compatible - regular expressions. - * ``select(key)`` -- interpret the field as a comma-separated list of items, with the items being - of the form "id:value". It finds the pair with the id equal to key and returns the corresponding value. - This function is particularly useful for extracting a value such as an ISBN from the set of identifiers - for a book. - * ``shorten(left chars, middle text, right chars)`` -- Return a shortened version of the field, - consisting of `left chars` characters from the beginning of the field, followed by `middle text`, - followed by `right chars` characters from the end of the string. `Left chars` and - `right chars` must be integers. For example, assume the title of the book - is `Ancient English Laws in the Times of Ivanhoe`, and you want it to fit in a space of at most 15 - characters. If you use ``{title:shorten(9,-,5)}``, the result will be `Ancient E-nhoe`. If the field's - length is less than ``left chars`` + ``right chars`` + the length of ``middle text``, then the field - will be used intact. For example, the title `The Dome` would not be changed. - * ``str_in_list(separator, string, found_val, ..., not_found_val)`` -- interpret the field as a - list of items separated by `separator`, comparing the `string` against each value in the list. - If the `string` matches a value (ignoring case), return `found_val`, otherwise return - `not_found_val`. If the string contains separators, then it is also treated as a list and each - value is checked. The `string` and `found_value` can be repeated as many times as desired, permitting - returning different values depending on the search. The strings are checked in order. The first match - is returned. - * ``subitems(start_index, end_index)`` -- This function is used to break apart lists of tag-like - hierarchical items such as genres. It interprets the field as a comma-separated list of tag-like items, - where each item is a period-separated list. Returns a new list made by first finding all the - period-separated tag-like items, then for each such item extracting the components from `start_index` to - `end_index`, then combining the results back together. The first component in a period-separated list - has an index of zero. If an index is negative, then it counts from the end of the list. As a special case, - an end_index of zero is assumed to be the length of the list. Examples:: - Assuming a #genre column containing "A.B.C": + * Assuming a #genre column containing "A.B.C" {#genre:subitems(0,1)} returns "A" {#genre:subitems(0,2)} returns "A.B" {#genre:subitems(1,0)} returns "B.C" - Assuming a #genre column containing "A.B.C, D.E": + * Assuming a #genre column containing "A.B.C, D.E": {#genre:subitems(0,1)} returns "A, D" {#genre:subitems(0,2)} returns "A.B, D.E" - * ``sublist(start_index, end_index, separator)`` -- interpret the field as a list of items separated - by `separator`, returning a new list made from the items from `start_index` to `end_index`. The first - item is number zero. If an index is negative, then it counts from the end of the list. As a special - case, an end_index of zero is assumed to be the length of the list. Examples assuming that the tags column - (which is comma-separated) contains "A, B ,C":: + * ``sublist(start_index, end_index, separator)`` -- interpret the value as a list of items separated by ``separator``, returning a new list made from the items from ``start_index`` to ``end_index``. The first item is number zero. If an index is negative, then it counts from the end of the list. As a special case, an end_index of zero is assumed to be the length of the list. + + Examples assuming that the tags column (which is comma-separated) contains "A, B ,C":: {tags:sublist(0,1,\,)} returns "A" {tags:sublist(-1,0,\,)} returns "C" {tags:sublist(0,-1,\,)} returns "A, B" - * ``swap_around_articles(separator)`` -- returns the val with articles moved to the end. The value ca - be a list, in which case each member of the list is processed. If the value is a list then you must - provide the list value separator. If no separator is provided then the value is treated as being a - single value, not a list. - * ``swap_around_comma()`` -- given a field with a value of the form ``B, A``, return ``A B``. - This is most useful for converting names in LN, FN format to FN LN. If there is no comma, - the function returns val unchanged. - * ``switch(pattern, value, pattern, value, ..., else_value)`` -- for each ``pattern, value`` pair, - checks if the field matches the regular expression ``pattern`` and if so, returns that ``value``. - If no ``pattern`` matches, then ``else_value`` is returned. You can have as many ``pattern, value`` pairs - as you wish. - * ``test(text if not empty, text if empty)`` -- return `text if not empty` if the field is not - empty, otherwise return `text if empty`. - * ``transliterate()`` -- Returns a string in a latin alphabet formed by approximating the sound of - the words in the source field. For example, if the source field is ``Фёдор Миха́йлович Достоевский`` - the function returns ``Fiodor Mikhailovich Dostoievskii``.' + * ``swap_around_articles(separator)`` -- returns the value with articles moved to the end. The value can be a list, in which case each item in the list is processed. If the value is a list then you must provide the ``separator``. If no ``separator`` is provided then the value is treated as being a single value, not a list. + * ``swap_around_comma()`` -- given a value of the form ``B, A``, return ``A B``. This is most useful for converting names in LN, FN format to FN LN. If there is no comma in the value then the function returns the value unchanged. + * ``switch(pattern, value, pattern, value, ..., else_value)`` -- for each ``pattern, value`` pair, checks if the field value matches the regular expression ``pattern`` and if so, returns the associated ``value``. If no ``pattern`` matches, then ``else_value`` is returned. You can have as many ``pattern, value`` pairs as you wish. The first match is returned. + * ``test(text if not empty, text if empty)`` -- return ``text if not empty`` if the value is not empty, otherwise return ``text if empty``. + * ``transliterate()`` -- Return a string in a latin alphabet formed by approximating the sound of the words in the source field. For example, if the source field is ``Фёдор Миха́йлович Достоевский`` this function returns ``Fiodor Mikhailovich Dostoievskii``. **Using functions and formatting in the same template** -Suppose you have an integer custom column called ``#myint`` that you want to -see with leading zeros, as in ``003``. To do this, you would use a format of ``0>3s``. However, by default, -if a number (integer or float) equals zero then the field produces the empty value, so zero values will -produce the empty string, not ``000``. If you really want to see ``000`` values, then you use both the -format string and the ``ifempty`` function to change the empty value back to a zero. -The field reference would be:: +Suppose you have an integer custom column ``#myint`` that you want displayed with leading zeros, as in ``003``. To do this, you would use a format of ``0>3s``. However, by default if a number (integer or float) equals zero then the value is displayed as the empty string so zero values will produce the empty string, not ``000``. If you want to see ``000`` values then you use both the format string and the ``ifempty`` function to change the empty value back to a zero. The template would be:: {#myint:0>3s:ifempty(0)} -Note that you can use the prefix and suffix as well. If you want the number to appear as ``[003]`` or ``[000]``, -then use the field:: +Note that you can use the prefix and suffix as well. If you want the number to appear as ``[003]`` or ``[000]``, then use the template:: {#myint:0>3s:ifempty(0)|[|]} @@ -296,8 +190,7 @@ then use the field:: General Program Mode ----------------------------------- -General Program Mode replaces the template with a program written in the Template Language. The syntax of the language -is shown by the following grammar: +General Program Mode replaces the template with a program written in the `template language`. The syntax of the language is defined by the following grammar:: program ::= 'program:' expression_list expression_list ::= top_expression [ ';' top_expression ]* @@ -306,25 +199,32 @@ is shown by the following grammar: and_expression ::= not_expression [ '&&' not_expression ]* not_expression ::= ['!' not_expression]* | compare_exp compare_expr ::= add_sub_expr [ compare_op add_sub_expr ] - compare_op ::= '==' | '!=' | '>=' | '>' | '<=' | '<' | 'in' | '==#' | '!=#' | '>=#' | '>#' | '<=#' | '<#' + compare_op ::= '==' | '!=' | '>=' | '>' | '<=' | '<' | 'in' | + '==#' | '!=#' | '>=#' | '>#' | '<=#' | '<#' add_sub_expr ::= times_div_expr [ add_sub_op times_div_expr ]* add_sub_op ::= '+' | '-' times_div_expr ::= unary_op_expr [ times_div_op unary_op_expr ]* times_div_op ::= '*' | '/' unary_op_expr ::= [ add_sub_op unary_op_expr ]* | expression - expression ::= identifier | constant | function | assignment | compare | if_expression | for_expression | '(' top_expression ')' + expression ::= identifier | constant | function | assignment | + compare | if_expression | for_expression | '(' top_expression ')' identifier ::= sequence of letters or ``_`` characters constant ::= " string " | ' string ' | number function ::= identifier '(' top_expression [ ',' top_expression ]* ')' assignment ::= identifier '=' top_expression - if_expression ::= 'if' top_expression 'then' expression_list [elif_expression] ['else' expression_list] 'fi' - elif_expression ::= 'elif' top_expression 'then' expression_list elif_expression | '' - for_expression ::= 'for' identifier 'in' top_expression [ 'separator' top_expression ] ':' expression_list 'rof' + if_expression ::= 'if' condition 'then' expression_list + [elif_expression] ['else' expression_list] 'fi' + condition ::= top_expression + elif_expression ::= 'elif' condition 'then' expression_list elif_expression | '' + for_expression ::= 'for' identifier 'in' list_expression + [ 'separator' separator_expr ] ':' expression_list 'rof' + list_expression ::= top_expression + separator_expr ::= top_expression -Comments are lines with a '#' character at the beginning of the line. +Comments are lines with a '#' character at the beginning of the line. You can't have comments that begin later in the line. A ``top_expression`` always has a value. The value of an ``expression_list`` is the value -of the last top_expression in the list. For example the value of the program (expression_list):: +of the last ``top_expression`` in the list. For example the value of the following ``expression_list``:: 1; 2; 'foobar'; 3 @@ -334,48 +234,36 @@ is 3. The operator precedence (order of evaluation) specified by the above grammar is: - * Function calls, constants, parenthesized expressions, statement expressions, - assignment expressions. In the template language, 'if', 'for', and assignment - return a value (see below). - * Unary plus (+) and minus (-). These operators evaluate right to left. - These and the other arithmetic operators return integers if the expression has a fractional part - equal to zero (i.e., 3.0). - * Multiply (*) and divide (/). These operators are associative and evaluate left to right. - Use parentheses if you want to change the order of evaluation. - * Add (+) and subtract (-). These operators are associative and evaluate left to right. - * Numeric and string comparisons. These operators return '1' (the number one) if the comparison is True, - otherwise the empty string (``''``). Comparisons are not associative: ``a < b < c`` is a syntax error. - * Unary logical not (!). This operator returns '1' if the expression is False (evaluates to the - empty string), otherwise ''. - * Logical and (&&). This operator returns '1' if both the left-hand and right-hand - expressions are True or the empty string '' if either is False. It is associative, evaluates left to - right, and does `short-circuiting `_. - * Logical or (||). This operator returns '1' if either the left-hand or right-hand expression is - True or '' if both are False. It is associative, evaluates left to right, and does short-circuiting. The - operator is an inclusive or, returning '1' if both the left- and right-hand expressions are True. + * Function calls, constants, parenthesized expressions, statement expressions, assignment expressions. In the template language, ``if``, ``for``, and assignments return a value (see below). + * Unary plus (``+``) and minus (``-``). These operators evaluate right to left. These and all the other arithmetic operators return integers if the expression results in a fractional part equal to zero. Example: if an expression returns ``3.0`` it is changed to ``3``. + * Multiply (``*``) and divide (``/``). These operators are associative and evaluate left to right. Use parentheses if you want to change the order of evaluation. + * Add (``+``) and subtract (``-``). These operators are associative and evaluate left to right. + * Numeric and string comparisons. These operators return ``1`` (the number one) if the comparison is True (a non-empty string), otherwise the empty string (``''``). Comparisons are not associative: ``a < b < c`` is a syntax error. + * Unary logical not (``!``). This operator returns '1' if the expression is False (evaluates to the empty string), otherwise ``''``. + * Logical and (``&&``). This operator returns '1' if both the left-hand and right-hand expressions are True or the empty string ``''`` if either is False. It is associative, evaluates left to right, and does `short-circuiting `_. + * Logical or (``||``). This operator returns ``'1'`` if either the left-hand or right-hand expression is True or ``''`` if both are False. It is associative, evaluates left to right, and does short-circuiting. The operator is an inclusive or, returning '1' if both the left- and right-hand expressions are True. **If Expressions** -If expressions evaluate the first top_expression, called the condition. The condition is True if it evaluates -to anything other than the empty string. If it is True then the expression list in the ``then`` section is -evaluated. If it is False then the expression in the ``elif`` or ``else`` expression is evaluated. The -``elif`` and ``else`` parts are optional. The words ``if``, ``then``, ``elif``, ``else``, and ``fi`` are -reserved; you cannot use them as identifier names. You can put newlines and white space wherever they -make sense. The condition is a top_expression; semicolons are not allowed. The expression_lists are -semicolon-separated sequences of template language top_expressions, including nested ifs. An if expression -returns the last expression in an evaluated expression_list, or '' if no expression list was evaluated. +``If`` expressions first evaluate the ``condition``, which is True if it evaluates to anything other than the empty string. If it is True then the ``expression_list`` in the ``then`` clause is evaluated. If it is False then the ``expression_list`` in the ``elif`` or ``else`` clause is evaluated. The ``elif`` and ``else`` parts are optional. The words ``if``, ``then``, ``elif``, ``else``, and ``fi`` are reserved; you cannot use them as identifier names. You can put newlines and white space wherever they make sense. The ``condition`` is a ``top_expression`` not an ``expression_list``; semicolons are not allowed. The ``expression_lists`` are semicolon-separated sequences of template language top_expressions. An ``if`` expression returns the result of the last ``top_expression`` in the evaluated ``expression_list``, or '' if no expression list was evaluated. -Examples: +Examples:: - * ``program: if field('series') then 'yes' else 'no' fi`` - * ``program: if field('series') then a = 'yes'; b = 'no' else a = 'no'; b='yes' fi; strcat(a, '-', b)`` + * program: if field('series') then 'yes' else 'no' fi + * program: + if field('series') then + a = 'yes'; + b = 'no' + else + a = 'no'; + b='yes' + fi; + strcat(a, '-', b) * Nested ``if`` example:: program: - if field('series') - then - if check_yes_no(field('#mybool'), '', '', '1') - then + if field('series') then + if check_yes_no(field('#mybool'), '', '', '1') then 'yes' else 'no' @@ -384,26 +272,22 @@ Examples: 'no series' fi -As said above, an ``if`` produces a value like any other language expression. This means that all the -following are valid: +As said above, like all ``expressions`` an ``if`` produces a value. This means that all the +following are equivalent:: - * ``program: if field('series') then 'foo' else 'bar' fi`` - * ``program: if field('series') then a = 'foo' else a = 'bar' fi; a`` - * ``program: a = if field('series') then 'foo' else 'bar' fi; a`` - * ``program: a = field(if field('series') then 'series' else 'title' fi); a`` + * program: if field('series') then 'foo' else 'bar' fi + * program: if field('series') then a = 'foo' else a = 'bar' fi; a + * program: a = if field('series') then 'foo' else 'bar' fi; a -** For Expressions** +As a last example, this program returns the word `series` if the book has a series otherwise the word `title`:: -The top_expression in ``for`` must evaluate to either a metadata field lookup key, for example ``tags`` or ``#genre``, -or a list of values. If the result is a valid lookup name then the field's value is fetched and the separator -specified for that field type is used. If the result isn't a valid lookup name then it is assumed to be a -list of values. If the optional keyword ``separator`` is supplied then the list values must be separated -by the result of evaluating the second top_expression. If the separator is not specified then the list -values must be separated by commas. Each resulting value in the list is assigned to the variable ``id`` then -the ``expression_list`` is evaluated. + program: a = field(if field('series') then 'series' else 'title' fi); a -Example: This template removes the first hierarchical name for each value in Genre (``#genre``), constructing a -list with the new names:: +**For Expressions** + +The ``list_expression`` in a ``for`` must evaluate to either a metadata field lookup key, for example ``tags`` or ``#genre``, or a list of values. If the result is a valid lookup key then the field's value is fetched and the separator specified for that field type is used. If the result isn't a valid lookup name then it is assumed to be a list of values. The list is assumed to be separated by commas unless the optional keyword ``separator`` is supplied, in which case the list values must be separated by the result of evaluating the ``separator_expr``. Each value in the list is assigned to the variable ``id`` then the ``expression_list`` is evaluated. + +Example: This template removes the first hierarchical name for each value in Genre (``#genre``), constructing a list with the new names:: program: new_tags = ''; @@ -413,109 +297,68 @@ list with the new names:: rof; new_tags -If the original Genre is ``History.Military, Science Fiction.Alternate History, ReadMe`` then the template returns -``Military, Alternate History, ReadMe``. You could use this template in calibre's -:guilabel:`Edit metadata in bulk -> Search & replace` with :guilabel:`Search for` set to ``template`` to strip -off the first level of the hierarchy and assign the resulting value to Genre. +If the original Genre is `History.Military, Science Fiction.Alternate History, ReadMe` then the template returns `Military, Alternate History, ReadMe`. You could use this template in calibre's +:guilabel:`Edit metadata in bulk -> Search & replace` with :guilabel:`Search for` set to ``template`` to strip off the first level of the hierarchy and assign the resulting value to Genre. -Note: the last line in the template, ``new_tags``, isn't strictly necessary in this case because ``for`` returns -the value of the last top_expression in the expression list. +Note: the last line in the template, ``new_tags``, isn't strictly necessary in this case because ``for`` returns the value of the last top_expression in the expression list. **Relational Operators** Relational operators return '1' if they evaluate to True, otherwise the empty string (''). -There are two forms of relational operator: string comparisons and numeric comparisons. The supported string -comparison operators are ``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``, and ``in``. -They do case-insensitive string comparison using lexical order. For the ``in`` operator, the result of -the left hand expression is interpreted as a regular expression pattern. The ``in`` operator is True if the -pattern matches the value of the right hand expression. The match is case-insensitive. +There are two forms of relational operator: string comparisons and numeric comparisons. The supported string comparison operators are ``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``, and ``in``. +They do case-insensitive string comparison using lexical order. For the ``in`` operator, the result of the left hand expression is interpreted as a regular expression pattern. The ``in`` operator is True if the pattern matches the result of the right hand expression. The match is case-insensitive. -The numeric comparison operators are ``==#``, ``!=#``, ``<#``, ``<=#``, ``>#``, ``>=#``. The left and right -expressions must evaluate to numeric values. Two exceptions: the string value "None" (undefined field) -and the empty string evaluate to the value zero. +The numeric comparison operators are ``==#``, ``!=#``, ``<#``, ``<=#``, ``>#``, ``>=#``. The left and right expressions must evaluate to numeric values with two exceptions: the string value "None" (undefined field) and the empty string evaluate to the value zero. Examples: - * ``program: field('series') == 'foo'`` returns '1' if the book's series is 'foo', otherwise ''. - * ``program: 'f.o' in field('series')`` returns '1' if the book's series matches the regular expression ``f.o``, otherwise ''. - * ``program: if field('series') != 'foo' then 'bar' else 'mumble' fi`` returns 'bar' if the book's series is not 'foo', else 'mumble'. - * ``program: if or(field('series') == 'foo', field('series') == '1632') then 'yes' else 'no' fi`` returns 'yes' if series is either - 'foo' or '1632', otherwise 'no'. - * ``program: if '^(foo|1632)$' in field('series') then 'yes' else 'no' fi`` returns 'yes' if series is either 'foo' or '1632', - otherwise 'no'. - * ``program: if '11' > '2' then 'yes' else 'no' fi`` returns 'no' because it does a lexical comparison. - * ``program: if '11' ># '2' then 'yes' else 'no' fi`` returns 'yes' because it does a numeric comparison. + * ``program: field('series') == 'foo'`` returns '1' if the book's series is 'foo', otherwise ``''``. + * ``program: 'f.o' in field('series')`` returns '1' if the book's series matches the regular expression ``f.o``, otherwise ``''``. + * ``program: if field('series') != 'foo' then 'bar' else 'mumble' fi`` returns ``bar`` if the book's series is not ``foo``, else ``mumble``. + * ``program: if or(field('series') == 'foo', field('series') == '1632') then 'yes' else 'no' fi`` returns ``yes`` if series is either `foo` or `1632`, otherwise ``no``. + * ``program: if '^(foo|1632)$' in field('series') then 'yes' else 'no' fi`` returns 'yes' if series is either `foo` or `1632`, otherwise 'no'. + * ``program: if '11' > '2' then 'yes' else 'no' fi`` returns `no` because it does a lexical comparison. + * ``program: if '11' ># '2' then 'yes' else 'no' fi`` returns `yes` because it does a numeric comparison. **Additional Available Functions** The following functions are available in addition to those described in :ref:`Single Function Mode `. -In General Program Mode the Single Function Mode functions require an additional first parameter -specifying the value to operate on. All parameters are top_expressions (see the grammar above). Note -that the definitive documentation for functions is available in the section -:ref:`Function reference `: - * ``and(value, value, ...)`` -- returns the string "1" if all values are not empty, otherwise returns - the empty string. This function works - well with test or first_non_empty. You can have as many values as you want. - * ``add(x, y, ...)`` -- returns the sum of its arguments. Throws an exception if an argument is not a number. - * ``assign(id, val)`` -- assigns val to id, then returns val. id must be an identifier, not an expression - * ``approximate_formats()`` -- return a comma-separated list of formats that at one point were associated - with the book. There is no - guarantee that the list is correct, although it probably is. This function can be called in Template Program - Mode using the template - ``{:'approximate_formats()'}``. Note that format names are always uppercase, as in EPUB. - * ``author_links(val_separator, pair_separator)`` -- returns a string containing a list of authors and that author's link values in - the form ``author1 val_separator author1link pair_separator author2 val_separator author2link`` etc. An author is separated from its link - value by the ``val_separator`` string with no added spaces. ``author:linkvalue`` pairs are separated by the ``pair_separator`` string - argument with no added spaces. It is up to you to choose separator strings that do not occur in author names or links. An author is included - even if the author link is empty. - * ``author_sorts(val_separator)`` -- returns a string containing a list of author's sort values for the authors of the book. The sort is the - one in the author metadata (different from the author_sort in books). The returned list has the form author sort 1 ``val_separator`` author - sort 2 etc. The author sort values in this list are in the same order as the authors of the book. If you want spaces around ``val_separator`` - then include them in the separator string +In General Program Mode the Single Function Mode functions require an additional first parameter +specifying the value to operate upon. All parameters are top_expressions (see the grammar above). Note that the definitive documentation for functions is available in the section :ref:`Function reference `: + + * ``add(x, y, ...)`` -- returns the sum of its arguments. Throws an exception if an argument is not a number. In most cases you can use the ``+`` operator instead of this function. + * ``and(value, value, ...)`` -- returns the string "1" if all values are not empty, otherwise returns the empty string. This function works well with test or first_non_empty. You can have as many values as you want. In most cases you can use the ``&&`` operator instead of this function. A reason it cannot be replaced is if short-circuiting will change the results. + * ``assign(id, val)`` -- assigns val to id, then returns val. id must be an identifier, not an expression. In most cases you can use the ``=`` operator instead of this function. + * ``approximate_formats()`` -- return a comma-separated list of formats that at one point were associated with the book. There is no guarantee that the list is correct, although it probably is. This and other zero-parameter functions can be called in Template Program Mode (see below) using the template ``{:'approximate_formats()'}``. Note that resulting format names are always uppercase, as in EPUB. + * ``author_links(val_separator, pair_separator)`` -- returns a string containing a list of authors and those authors' link values in the form: + + ``author1 val_separator author1_link pair_separator author2 val_separator author2_link`` etc. + + An author is separated from its link value by the ``val_separator`` string with no added spaces. ``author:linkvalue`` pairs are separated by the ``pair_separator`` string argument with no added spaces. It is up to you to choose separator strings that do not occur in author names or links. An author is included even if the author link is empty. + * ``author_sorts(val_separator)`` -- returns a string containing a list of author's sort values for the authors of the book. The sort is the one in the author metadata information (different from the author_sort in books). The returned list has the form ``author sort 1`` ``val_separator`` ``author sort 2`` etc. The author sort values in this list are in the same order as the authors of the book. If you want spaces around ``val_separator`` then include them in the ``val_separator`` string. * ``booksize()`` -- returns the value of the calibre 'size' field. Returns '' if there are no formats. - * ``check_yes_no(field_name, is_undefined, is_false, is_true)`` -- checks the value of the yes/no field named by the lookup key - ``field_name`` for a value specified by the parameters, returning "yes" if a match is found, otherwise returning an empty string. Set the - parameter ``is_undefined``, ``is_false``, or ``is_true`` to 1 (the number) to check that condition, otherwise set it to 0. Example:: + * ``check_yes_no(field_name, is_undefined, is_false, is_true)`` -- checks the value of the yes/no field named by the lookup key ``field_name`` for a value specified by the parameters, returning ``'yes'`` if a match is found, otherwise returning the empty string. Set the parameter ``is_undefined``, ``is_false``, or ``is_true`` to 1 (the number) to check that condition, otherwise set it to 0. Example:: check_yes_no("#bool", 1, 0, 1) - returns "yes" if the yes/no field ``"#bool"`` is either undefined (neither True nor False) or True. More than one of ``is_undefined``, - ``is_false``, or ``is_true`` can be set to 1. This function is usually used by the ``test()`` or ``is_empty()`` functions. - * ``ceiling(x)`` -- returns the smallest integer greater than or equal to x. Throws an exception if x is not a number. - * ``cmp(x, y, lt, eq, gt)`` -- compares x and y after converting both to numbers. Returns ``lt`` if x < y. Returns ``eq`` if x == y. - Otherwise returns ``gt``. - * ``connected_device_name(storage_location)`` -- if a device is connected then return the device name, otherwise return the empty string. - Each storage location on a device can have a different name. The location names are 'main', 'carda' and 'cardb'. This function works - only in the GUI. - * ``connected_device_uuid(storage_location)`` -- if a device is connected then return the device uuid (unique id), - otherwise return the empty string. Each storage location on a device has a different uuid. The location names are ``'main'``, - ``'carda'`` and ``'cardb'``. This function works only in the GUI. - * ``current_library_name()`` -- return the last name on the path to the current calibre library. This function can be called in - Template Program Mode using the template ``{:'current_library_name()'}``. - * ``current_library_path()`` -- return the path to the current calibre library. This function can be called in Template Program Mode - using the template ``{:'current_library_path()'}``. - * ``days_between(date1, date2)`` -- return the number of days between ``date1`` and ``date2``. The number is positive if ``date1`` - is greater than ``date2``, otherwise negative. If either ``date1`` or ``date2`` are not dates, the function returns the empty string. - * ``divide(x, y)`` -- returns ``x / y``. Throws an exception if either ``x`` or ``y`` are not numbers. - * ``eval(string)`` -- evaluates the string as a program, passing the local variables (those ``assign`` ed to). This permits using the - template processor to construct complex results from local variables. Because the `{` and `}` characters are special, you must use - `[[` for the `{` character and `]]` for the '}' character; they are converted automatically. Note also that prefixes and suffixes - (the `|prefix|suffix` syntax) cannot be used in the argument to this function when using Template Program Mode. - * ``field(name)`` -- returns the metadata field named by ``name``. - * ``field_exists(field_name)`` -- checks if a field (column) named ``field_name`` exists, returning '1' if so and '' if not. - * ``finish_formatting(val, fmt, prefix, suffix)`` -- apply the format, - prefix, and suffix to a value in the same way as done in a template like - ``{series_index:05.2f| - |- }``. This function is provided to ease - conversion of complex single-function- or template-program-mode templates - to :ref:`General Program Mode ` (see below) to take - advantage of GPM template compilation. For example, the following program - produces the same output as the above template:: + returns ``'yes'`` if the yes/no field ``"#bool"`` is either undefined (neither True nor False) or True. More than one of ``is_undefined``, ``is_false``, or ``is_true`` can be set to 1. + * ``ceiling(x)`` -- returns the smallest integer greater than or equal to ``x``. Throws an exception if ``x`` is not a number. + * ``cmp(x, y, lt, eq, gt)`` -- compares ``x`` and ``y`` after converting both to numbers. Returns ``lt`` if ``x`` < ``y``. Returns ``eq`` if ``x`` == ``y``, otherwise returns ``gt``. + * ``connected_device_name(storage_location_key)`` -- if a device is connected then return the device name, otherwise return the empty string. Each storage location on a device can have a different device name. The ``storage_location_key`` names are ``'main'``, ``'carda'`` and ``'cardb'``. This function works only in the GUI. + * ``connected_device_uuid(storage_location_key)`` -- if a device is connected then return the device uuid (unique id), otherwise return the empty string. Each storage location on a device has a different uuid. The ``storage_location_key`` location names are ``'main'``, ``'carda'`` and ``'cardb'``. This function works only in the GUI. + * ``current_library_name()`` -- return the last name on the path to the current calibre library. + * ``current_library_path()`` -- return the full path to the current calibre library. + * ``days_between(date1, date2)`` -- return the number of days between ``date1`` and ``date2``. The number is positive if ``date1`` is greater than ``date2``, otherwise negative. If either ``date1`` or ``date2`` are not dates, the function returns the empty string. + * ``divide(x, y)`` -- returns ``x / y``. Throws an exception if either ``x`` or ``y`` are not numbers. This function can usually be replaced by the ``/`` operator. + * ``eval(string)`` -- evaluates the string as a program, passing the local variables (those ``assign`` ed to). This permits using the template processor to construct complex results from local variables. In Template Program Mode, because the `{` and `}` characters are interpreted before the template is evaluated you must use `[[` for the `{` character and `]]` for the ``}`` character. they are converted automatically. Note also that prefixes and suffixes (the `|prefix|suffix` syntax) cannot be used in the argument to this function when using Template Program Mode. + * ``field(name)`` -- returns the value of the metadata field named by ``name``. + * ``field_exists(field_name)`` -- checks if a field (column) named ``field_name`` exists, returning ``'1'`` if so and ``''`` if not. + * ``finish_formatting(val, fmt, prefix, suffix)`` -- apply the format, prefix, and suffix to a value in the same way as done in a template like ``{series_index:05.2f| - |- }``. This function is provided to ease conversion of complex single-function- or template-program-mode templates to General Program Mode Templates. For example, the following program produces the same output as the above template:: program: finish_formatting(field("series_index"), "05.2f", " - ", " - ") - Another example: for the template ``{series:re(([^\s])[^\s]+(\s|$),\1)}{series_index:0>2s| - | - }{title}`` use:: program: @@ -525,20 +368,15 @@ that the definitive documentation for functions is available in the section field('title') ) - * ``first_matching_cmp(val, cmp1, result1, cmp2, r2, ..., else_result)`` -- compares ``val < cmpN`` in sequence, returning resultN for the - first comparison that succeeds. Returns else_result if no comparison succeeds. Example:: + * ``first_matching_cmp(val, cmp1, result1, cmp2, r2, ..., else_result)`` -- compares ``val < cmpN`` in sequence, returning resultN for the first comparison that succeeds. Returns else_result if no comparison succeeds. Example:: first_matching_cmp(10,5,"small",10,"middle",15,"large","giant") - returns "large". The same example with a first value of 16 returns "giant". - * ``first_non_empty(value, value, ...)`` -- returns the first value that is not empty. If all values are empty, then the empty - value is returned. You can have as many values as you want. - * ``floor(x)`` -- returns the largest integer less than or equal to x. Throws an exception if x is not a number. - * ``format_date(val, format_string)`` -- format the value, which must be a date - field, using the format_string, returning a string. The formatting codes - are:: + * ``first_non_empty(value, value, ...)`` -- returns the first ``value`` that is not empty. If all values are empty, then the empty value is returned. You can have as many values as you want. + * ``floor(x)`` -- returns the largest integer less than or equal to ``x``. Throws an exception if ``x`` is not a number. + * ``format_date(val, format_string)`` -- format the value, which must be a date string, using the format_string, returning a string. The formatting codes are:: d : the day as number without a leading zero (1 to 31) dd : the day as number with a leading zero (01 to 31) @@ -560,107 +398,60 @@ that the definitive documentation for functions is available in the section AP : use a 12-hour clock instead of a 24-hour clock, with 'AP' replaced by the localized string for AM or PM. iso : the date with time and timezone. Must be the only format present. + You might get unexpected results if the date you are formatting contains localized month names, which can happen if you changed the date format tweaks to contain ``MMMM``. In this case, instead of using something like ``format_date(field('pubdate'), 'yyyy')``, write the template using ``raw_field``, as in ``format_date(raw_field('pubdate'), 'yyyy')``. + * ``formats_modtimes(date_format_string)`` -- return a comma-separated list of colon-separated items ``FMT:DATE`` representing modification times for the formats of a book. The ``date_format_string`` parameter specifies how the date is to be formatted. See the ``format_date()`` function for details. You can use the ``select`` function to get the modification time for a specific format. Note that format names are always uppercase, as in EPUB. + * ``formats_paths()`` -- return a comma-separated list of colon-separated items ``FMT:PATH`` giving the full path to the formats of a book. You can use the select function to get the path for a specific format. Note that format names are always uppercase, as in EPUB. + * ``formats_sizes()`` -- return a comma-separated list of colon-separated ``FMT:SIZE`` items giving the sizes in bytes of the formats of a book. You can use the select function to get the size for a specific format. Note that format names are always uppercase, as in EPUB. + * ``fractional_part(x)`` -- returns the value after the decimal point. For example, ``fractional_part(3.14)`` returns ``0.14``. Throws an exception if ``x`` is not a number. + * ``has_cover()`` -- return ``'Yes'`` if the book has a cover, otherwise the empty string. + * ``is_marked()`` -- check whether the book is `marked` in calibre. If it is then return the value of the mark, either ``'true'`` (lower case) or a comma-separated list of named marks. Returns ``''`` (the empty string) if the book is not marked. This function works only in the GUI. + * ``list_contains(separator, pattern, found_val, ..., not_found_val)`` -- (Alias of ``in_list``) Interpret the value as a list of items separated by ``separator``, evaluating the ``pattern`` against each value in the list. If the ``pattern`` matches any value, return ``found_val``, otherwise return ``not_found_val``. The ``pattern`` and ``found_value`` can be repeated as many times as desired, permitting returning different values depending on the search. The patterns are checked in order. The first match is returned. Aliases: ``in_list()``, ``list_contains()`` + * ``list_count(separator)`` -- interprets the value as a list of items separated by ``separator``, returning the number of items in the list. Aliases: ``count()``, ``list_count()`` + * ``list_count_matching(list, pattern, separator)`` -- interprets ``list`` as a list of items separated by ``separator``, returning the number of items in the list that match the regular expression ``pattern``. Aliases: ``list_count_matching()``, ``count_matching()`` + * ``list_difference(list1, list2, separator)`` -- return a list made by removing from ``list1`` any item found in ``list2`` using a case-insensitive comparison. The items in ``list1`` and ``list2`` are separated by separator, as are the items in the returned list. + * ``list_equals(list1, sep1, list2, sep2, yes_val, no_val)`` -- return ``yes_val`` if ``list1`` and `list2` contain the same items, otherwise return ``no_val``. The items are determined by splitting each list using the appropriate separator character (``sep1`` or ``sep2``). The order of items in the lists is not relevant. The comparison is case-insensitive. + * ``list_intersection(list1, list2, separator)`` -- return a list made by removing from ``list1`` any item not found in ``list2``, using a case-insensitive comparison. The items in ``list1`` and ``list2`` are separated by separator, as are the items in the returned list. + * ``list_re(src_list, separator, include_re, opt_replace)`` -- Construct a list by first separating ``src_list`` into items using the ``separator`` character. For each item in the list, check if it matches ``include_re``. If it does then add it to the list to be returned. If ``opt_replace`` is not the empty string then apply the replacement before adding the item to the returned list. + * ``list_re_group(src_list, separator, include_re, search_re, template_for_group_1, for_group_2, ...)`` -- Like list_re except replacements are not optional. It uses ``re_group(item, search_re, template ...)`` when doing the replacements. + * ``list_remove_duplicates(list, separator)`` -- return a list made by removing duplicate items in ``list``. If items differ only in case then the last is returned. The items in ``list`` are separated by ``separator``, as are the items in the returned list. + * ``list_sort(list, direction, separator)`` -- return ``list`` sorted using a case-insensitive lexical sort. If ``direction`` is zero, ``list`` is sorted ascending, otherwise descending. The list items are separated by ``separator``, as are the items in the returned list. + * ``list_union(list1, list2, separator)`` -- return a list made by merging the items in ``list1`` and ``list2``, removing duplicate items using a case-insensitive comparison. If items differ in case, the one in ``list1`` is used. The items in ``list1`` and ``list2`` are separated by ``separator``, as are the items in the returned list. Aliases: ``merge_lists()``, ``list_union()`` + * ``mod(x, y)`` -- returns the ``floor`` of the remainder of ``x / y``. Throws an exception if either ``x`` or ``y`` is not a number. + * ``multiply(x, y, ...)`` -- returns the product of its arguments. Throws an exception if any argument is not a number. This function can usually be replaced by the ``*`` operator. + * ``not(value)`` -- returns the string "1" if the value is empty, otherwise returns the empty string. This function can usually be replaced with the unary not (``!``) operator. + * ``ondevice()`` -- return the string ``'Yes'`` if ``ondevice`` is set, otherwise return the empty string. + * ``or(value, value, ...)`` -- returns the string ``"1"`` if any value is not empty, otherwise returns the empty string. You can have as many values as you want. This function can usually be replaced by the ``||`` operator. A reason it cannot be replaced is if short-circuiting will change the results. + * ``print(a, b, ...)`` -- prints the arguments to standard output. Unless you start calibre from the command line (``calibre-debug -g``), the output will go to a black hole. The ``print`` function always returns the empty string. + * ``raw_field(name [, optional_default]))`` -- returns the metadata field named by name without applying any formatting. It evaluates and returns the optional second argument ``optional_default`` if the field's value is undefined (``None``). + * ``raw_list(``lookup_name``, separator)`` -- returns the metadata list named by ``lookup_name`` without applying any formatting or sorting and with items separated by separator. + * ``re_group(value, pattern, template_for_group_1, for_group_2, ...)`` -- return a string made by applying the regular expression pattern to ``value`` and replacing each matched instance with the the value returned by the corresponding template. In Template Program Mode, like for the ``template`` and the ``eval`` functions, you use ``[[`` for ``{`` and ``]]`` for ``}``. - You might get unexpected results if the date you are formatting contains localized month names, which can happen if you changed the - format tweaks to contain ``MMMM``. In this case, instead of using something like ``{pubdate:format_date(yyyy)}``, write the template - using Template Program Mode as in ``{:'format_date(raw_field('pubdate'),'yyyy')'}``. - * ``formats_modtimes(format_string)`` -- return a comma-separated list of colon-separated items representing modification times for the - formats of a book. The format_string parameter specifies how the date is to be formatted. See the `format_date()` function for details. - You can use the select function to get the mod time for a specific format. Note that format names are always uppercase, as in EPUB. - * ``formats_paths()`` -- return a comma-separated list of colon-separated items representing full path to the formats of a book. You can - use the select function to get the path for a specific format. Note that format names are always uppercase, as in EPUB. - * ``formats_sizes()`` -- return a comma-separated list of colon-separated items representing sizes in bytes of the formats of a book. - You can use the select function to get the size for a specific format. Note that format names are always uppercase, as in EPUB. - * ``fractional_part(x)`` -- returns the value after the decimal point. For example, ``fractional_part(3.14)`` returns ``0.14``. - Throws an exception if ``x`` is not a number. - * ``has_cover()`` -- return ``Yes`` if the book has a cover, otherwise return the empty string. - * ``is_marked()`` -- check whether the book is `marked` in calibre. If it is then return the value of the mark, - either `true` (lower case) or the comma-separated list of named marks. Returns '' (the empty string) if the book is not marked. - This function works only in the GUI. - * ``list_contains(separator, pattern, found_val, ..., not_found_val)`` -- (Alias of ``in_list``) Interpret the field as a list - of items separated by `separator`, evaluating the `pattern` against each value in the list. If the `pattern` matches a value, - return `found_val`, otherwise return `not_found_val`. The `pattern` and `found_value` can be repeated as many times as desired, - permitting returning different values depending on the search. The patterns are checked in order. The first match is returned. - Aliases: ``in_list()``, ``list_contains()`` - * ``list_count(separator)`` -- interprets the value as a list of items separated by `separator`, returning the number of items - in the list. Aliases: ``count()``, ``list_count()`` - * ``list_count_matching(list, pattern, separator)`` -- interprets ``list`` as a list of items separated by ``separator``, - returning the number of items in the list that match the regular expression ``pattern``. - Aliases: ``list_count_matching()``, ``count_matching()`` - * ``list_difference(list1, list2, separator)`` -- return a list made by removing from `list1` any item found in `list2`, - using a case-insensitive comparison. The items in `list1` and `list2` are separated by separator, as are the items in the returned list. - * ``list_equals(list1, sep1, list2, sep2, yes_val, no_val)`` -- return `yes_val` if `list1` and `list2` contain the same items, - otherwise return `no_val`. The items are determined by splitting each list using the appropriate separator character (`sep1` or `sep2`). - The order of items in the lists is not relevant. The comparison is case-insensitive. - * ``list_intersection(list1, list2, separator)`` -- return a list made by removing from `list1` any item not found in `list2`, using a - case-insensitive comparison. The items in `list1` and `list2` are separated by separator, as are the items in the returned list. - * ``list_re(src_list, separator, include_re, opt_replace)`` -- Construct a list by first separating `src_list` into items using the - `separator` character. For each item in the list, check if it matches `include_re`. If it does, then add it to the list to be returned. - If `opt_replace` is not the empty string, then apply the replacement before adding the item to the returned list. - * ``list_re_group(src_list, separator, include_re, search_re, template_for_group_1, for_group_2, ...)`` -- Like list_re except - replacements are not optional. It uses re_group(item, search_re, template ...) when doing the replacements. - * ``list_remove_duplicates(list, separator)`` -- return a list made by removing duplicate items in the source list. If items - differ only in case, the last of them is returned. The items in source list are separated by separator, as are - the items in the returned list. - * ``list_sort(list, direction, separator)`` -- return list sorted using a case-insensitive sort. If ``direction`` is zero, ``list`` is - sorted ascending, otherwise descending. The list items are separated by separator, as are the items in the returned list. - * ``list_union(list1, list2, separator)`` -- return a list made by merging the items in ``list1`` and ``list2``, removing - duplicate items using a case-insensitive comparison. If items differ in case, the one in ``list1`` is used. The items - in ``list1`` and ``list2`` are separated by ``separator``, as are the items in the returned list. - Aliases: ``merge_lists()``, ``list_union()`` - * ``mod(x)`` -- returns the remainder of ``x / y``, where ``x``, ``y``, and the result are integers. Throws an exception if either ``x`` or - ``y`` is not a number. - * ``multiply(x, y, ...)`` -- returns the product of its arguments. Throws an exception if any argument is not a number. - * ``not(value)`` -- returns the string "1" if the value is empty, otherwise returns the empty string. This function works well - with test or first_non_empty. - * ``ondevice()`` -- return the string "Yes" if ``ondevice`` is set, otherwise return the empty string - * ``or(value, value, ...)`` -- returns the string ``"1"`` if any value is not empty, otherwise returns the empty string. This function works - well with test or `first_non_empty`. You can have as many values as you want. - * ``print(a, b, ...)`` -- prints the arguments to standard output. Unless you start calibre from the command line (``calibre-debug -g``), - the output will go to a black hole. - * ``raw_field(name [, optional_default]))`` -- returns the metadata field named by name without applying any formatting. - It evaluates and returns the optional second argument ``default`` if the field is undefined (``None``). - * ``raw_list(name, separator)`` -- returns the metadata list named by name without applying any formatting or sorting and with items separated by separator. - * ``re_group(val, pattern, template_for_group_1, for_group_2, ...)`` -- return a string made by applying the regular expression pattern to - the val and replacing each matched instance with the string computed by replacing each matched group by the value returned by the corresponding - template. The original matched value for the group is available as ``$``. In Template Program Mode, like for the template and the eval functions, - you use [[ for { and ]] for }. The following example in Template Program Mode looks for series with more than one word and uppercases the first word:: + The following example looks for a series with more than one word and uppercases the first word:: - {series:'re_group($, "(\S* )(.*)", "[[$:uppercase()]]", "[[$]]")'} + program: re_group(field('series'), "(\S* )(.*)", "{$:uppercase()}", "{$}")'} - * ``round(x)`` -- returns the nearest integer to x. Throws an exception if x is not a number. + * ``round(x)`` -- returns the nearest integer to ``x``. Throws an exception if ``x`` is not a number. * ``series_sort()`` -- returns the series sort value. - * ``'split(list_val, sep, id_prefix)`` -- splits the ``list_val`` into separate values using ``sep``, then assigns the values to variables named - ``id_prefix_N`` where N is the position of the value in the list. The first item has position 0 (zero). The function returns the last element - in the list. Example:: + * ``split(list_val, sep, id_prefix)`` -- splits ``list_val`` into separate values using ``sep``, then assigns the values to variables named ``id_prefix_N`` where N is the position of the value in the list. The first item has position 0 (zero). The function returns the last element in the list. + + Example:: split('one, two, foo', ',', 'var') - is equivalent to:: + is equivalent to:: var_0 = 'one'; var_1 = 'two'; var_3 = 'foo * ``strcat(a, b, ...)`` -- can take any number of arguments. Returns a string formed by concatenating all the arguments. - * ``strcat_max(max, string1, prefix2, string2, ...)`` -- Returns a string formed by concatenating the arguments. The returned value is - initialized to ``string1``. ``prefix, string`` pairs are added to the end of the value as long as the resulting string length is less than ``max``. - Returns ``string1`` even if ``string1`` is longer than ``max``. You can pass as many ``prefix, string`` pairs as you wish. - * ``strcmp(x, y, lt, eq, gt)`` -- does a case-insensitive comparison ``x`` and ``y`` as strings. Returns ``lt`` if ``x < y``. - Returns ``eq`` if ``x == y``. Otherwise returns ``gt``. - * ``strlen(a)`` -- Returns the length of the string passed as the argument. - * ``substr(str, start, end)`` -- returns the ``start``'th through the ``end``'th characters of ``str``. The first character in ``str`` - is the zero'th character. If end is negative, then it indicates that many characters counting from the right. If end is zero, then it - indicates the last character. For example, ``substr('12345', 1, 0)`` returns ``'2345'``, and ``substr('12345', 1, -1)`` returns ``'234'``. - * ``subtract(x, y)`` -- returns ``x - y``. Throws an exception if either ``x`` or ``y`` are not numbers. - * ``today()`` -- return a date string for today. This value is designed for use in `format_date` or `days_between`, but can be manipulated - like any other string. The date is in ISO format. - * ``template(x)`` -- evaluates ``x`` as a template. The evaluation is done in its own context, meaning that variables are not shared between - the caller and the template evaluation. Because the `{` and `}` characters are special, you must use `[[` for the `{` character and - `]]` for the '}' character; they are converted automatically. For example, ``template('[[title_sort]]') will evaluate the template - ``{title_sort}`` and return its value. Note also that prefixes and suffixes (the `|prefix|suffix` syntax) cannot be used in the argument - to this function when using Template Program Mode. - + * ``strcat_max(max, string1, prefix2, string2, ...)`` -- Returns a string formed by concatenating the arguments. The returned value is initialized to ``string1``. Strings made from ``prefix, string`` pairs are added to the end of the value as long as the resulting string length is less than ``max``. Prefixes can be empty. Returns ``string1`` even if ``string1`` is longer than ``max``. You can pass as many ``prefix, string`` pairs as you wish. + * ``strcmp(x, y, lt, eq, gt)`` -- does a case-insensitive lexical comparison of ``x`` and ``y``. Returns ``lt`` if ``x < y``, ``eq`` if ``x == y``, otherwise ``gt``. + * ``strlen(value)`` -- Returns the length of the string ``value``. + * ``substr(str, start, end)`` -- returns the ``start``'th through the ``end``'th characters of ``str``. The first character in ``str`` is the zero'th character. If ``end`` is negative, then it indicates that many characters counting from the right. If ``end`` is zero, then it indicates the last character. For example, ``substr('12345', 1, 0)`` returns ``'2345'``, and ``substr('12345', 1, -1)`` returns ``'234'``. + * ``subtract(x, y)`` -- returns ``x - y``. Throws an exception if either ``x`` or ``y`` are not numbers. This function can usually be replaced by the ``-`` operator. + * ``today()`` -- return a date+time string for today (now). This value is designed for use in `format_date` or `days_between`, but can be manipulated like any other string. The date is in `ISO `_ date/time format. + * ``template(x)`` -- evaluates ``x`` as a template. The evaluation is done in its own context, meaning that variables are not shared between the caller and the template evaluation. .. _template_mode: @@ -669,31 +460,21 @@ More complex programs in templates - Template Program Mode Template Program Mode is a blend of :ref:`General Program Mode ` and :ref:`Single Function Mode `. Template Program Mode differs from -Single Function Mode in that it permits -writing template expressions that refer to other metadata fields, use nested functions, modify variables, -and do arithmetic. It differs from General Program Mode in that the template is contained -between ``{`` and ``}`` characters and doesn't begin with the word ``program:``. The program portion -of the template is a General Program Mode expression list. +Single Function Mode in that it permits writing template expressions that refer to other metadata fields, use nested functions, modify variables, and do arithmetic. It differs from General Program Mode in that the template is contained between ``{`` and ``}`` characters and doesn't begin with the word ``program:``. The program portion of the template is a General Program Mode expression list. Example: assume you want a template to show the series for a book if it has one, otherwise show -the value of a custom field #genre. You cannot do this in the :ref:`Single Function Mode ` because -you cannot make reference to another metadata field within a template expression. In Template Program Mode -you can, as the following expression demonstrates:: +the value of a custom field #genre. You cannot do this in the :ref:`Single Function Mode ` because you cannot make reference to another metadata field within a template expression. In Template Program Mode you can, as the following expression demonstrates:: {#series:'ifempty($, field('#genre'))'} The example shows several things: - * Template Program Mode is used if the expression begins with ``:'`` and ends with ``'``. Anything else is - assumed to be in :ref:`Single Function Mode `. - * the variable ``$`` stands for the field the expression is operating upon, ``#series`` in this case. - * functions must be given all their arguments. There is no default value. For example, the standard - built-in functions must be given an additional initial parameter indicating the source field, which is - a significant difference from single-function mode. + * Template Program Mode is used if the expression begins with ``:'`` and ends with ``'``. Anything else is assumed to be in :ref:`Single Function Mode `. + * the variable ``$`` stands for the field named in the template: the expression is operating upon, ``#series`` in this case. + * functions must be given all their arguments. There is no default value. For example, the standard built-in functions must be given an additional initial parameter indicating the source field. * white space is ignored and can be used anywhere within the expression. * constant strings are enclosed in matching quotes, either ``'`` or ``"``. - Another example of a complex but rather silly program might help make things clearer:: {series_index:' @@ -707,26 +488,12 @@ Another example of a complex but rather silly program might help make things cle This program does the following: - * specify that the field being looked at is series_index. The variable ``$`` is set to its value. - * calls the ``substr`` function, which takes 3 parameters ``(str, start, end)``. It returns a string formed by extracting the start - through end characters from string, zero-based (the first character is character zero). In this case the string will be computed by the - ``strcat`` function, the start is 0, and the end is 6. In this case it will return the first 6 characters of the string returned by - ``strcat``, which must be evaluated before substr can return. - * calls the ``strcat`` (string concatenation) function. Strcat accepts 1 or more arguments, and returns a string formed by concatenating - all the values. In this case there are three arguments. The first parameter is the value in ``$``, which here is the value of ``series_index``. - The second paremeter is the constant string ``'->'``. The third parameter is the value returned by the ``cmp`` function, which must be fully - evaluated before ``strcat`` can return. - * The ``cmp`` function takes 5 arguments ``(x, y, lt, eq, gt)``. It compares ``x`` and ``y`` and returns the third argument ``lt`` if ``x < y``, - the fourth argument ``eq`` if ``x == y``, and the fifth argument ``gt`` if ``x > y``. As with all functions, all of the parameters can be - statements. In this case the first parameter (the value for ``x``) is the result of dividing the ``series_index`` by 2. The second parameter - ``y`` is the constant ``1``. The third parameter ``lt`` is a statement (more later). The fourth parameter ``eq`` is the constant string - ``'eq'``. The fifth parameter is the constant string ``'gt'``. - * The third parameter (the one for ``lt``) is a statement, or a sequence of expressions. Remember that a statement (a sequence of - semicolon-separated expressions) is also an expression, returning the value of the last expression in the list. In this case, the program - first assigns the value ``1`` to a local variable ``c``, then returns a substring made by extracting the ``c``'th character to the end. - Since ``c`` always contains the constant ``1``, the substring will return the second through ``end``'th characters, or ``'t123'``. - * Once the statement providing the value to the third parameter is executed, ``cmp`` can return a value. At that point, ``strcat` can return - a value, then ``substr`` can return a value. The program then terminates. + * specifies that the value being used is the field `series_index`. The variable ``$`` is set to its value. + * calls the ``substr`` function, which takes 3 parameters ``(str, start, end)``. It returns a string formed by extracting the ``start`` through ``end`` characters from string, zero-based (the first character is character zero). In this case ``substr`` will return the first 6 characters of the string returned by ``strcat``, which must be evaluated before substr can return. + * calls the ``strcat`` (string concatenation) function. Strcat accepts 1 or more arguments, and returns a string formed by concatenating all the arguments. In this case there are three arguments. The first parameter is the value in ``$``, here the value of ``series_index``. The second paremeter is the constant string ``'->'``. The third parameter is the value returned by the ``cmp`` function, which must be fully evaluated before ``strcat`` can return. + * The ``cmp`` function takes 5 arguments ``(x, y, lt, eq, gt)``. It compares ``x`` and ``y`` and returns the third argument ``lt`` if ``x < y``, the fourth argument ``eq`` if ``x == y``, and the fifth argument ``gt`` if ``x > y``. As with all functions, all of the parameters can be an ``expression list``. In this case the first argument (the value for ``x``) is the result of dividing the ``series_index`` by 2. The second argument ``y`` is the constant ``1``. The third argument ``lt`` is an ``expression_list`` (more later). The fourth argument ``eq`` is the constant string ``'eq'``. The fifth argument is the constant string ``'gt'``. + * The third argument (the one for ``lt``) is an ``expression_list``, or a sequence of ``top_expressions``. Remember that an ``expression_list`` is also an expression, returning the value of the last ``top_expression in the list``. In this case, the program first assigns the value ``1`` to a local variable ``c``, then returns a substring made by extracting the ``c``'th character to the end. Since ``c`` always contains the constant ``1``, the substring will return the second through ``end``'th characters, or ``'t123'``. + * Once the statement providing the value to the third parameter is executed, ``cmp`` can return a value. At that point, ``strcat` can return a value, then ``substr`` can return a value. The program then terminates. For various values of series_index, the program returns: @@ -737,32 +504,21 @@ For various values of series_index, the program returns: * series_index == 3, result = ``prefix 3->gt suffix`` **All the functions listed under :ref:`Single Function Mode ` -and :ref:`General Program Mode ` can be used in Template Program Mode**. For functions -documented under :ref:`Single Function Mode ` you must supply the value the function is to act -upon as the first parameter in addition to the documented parameters. For example, -in :ref:`General Program Mode ` the parameters of the `test` function -are ``test(x, text_if_not_empty, text_if_empty)``. The `x` parameter, which is -the value to be tested, will almost always be a variable or a function call, often `field()`. +and :ref:`General Program Mode ` can be used in Template Program Mode**. + +For functions documented under :ref:`Single Function Mode ` you must supply the value the function is to act upon as the first parameter in addition to the documented parameters. In Template Program Mode you can use ``$`` to access the value specified for the template. In General Program Mode that first parameter is frequently be a variable or a function call, often `field()`. Stored General Program Mode Templates ---------------------------------------- -:ref:`General Program Mode ` supports saving templates and calling those templates from another template. -You save templates using :guilabel:`Preferences->Advanced->Template functions`. More information is provided in -that dialog. You call a template the same way you call a function, passing positional arguments if desired. -An argument can be any expression. Examples of calling a template, assuming the stored template is named ``foo``: +:ref:`General Program Mode ` supports saving templates and calling those templates from another template. You save templates using :guilabel:`Preferences->Advanced->Template functions`. More information is provided in that dialog. You call a template the same way you call a function, passing positional arguments if desired. An argument can be any expression. Examples of calling a template, assuming the stored template is named ``foo``: * ``foo()`` -- call the template passing no arguments. * ``foo(a, b)`` call the template passing the values of the two variables ``a`` and ``b``. * ``foo(if field('series') then field('series_index') else 0 fi)`` -- if the book has a ``series`` then pass the ``series_index``, otherwise pass the value ``0``. -In the stored template you retrieve the arguments passed in the call using the ``arguments`` function. It both -declares and initializes local variables, effectively parameters. The variables are positional; they get -the value of the value given in the call in the same position. If the corresponding parameter is not provided -in the call then ``arguments`` assigns that variable the provided default value. If there is no -default value then the variable is set to the empty string. For example, the -following ``arguments`` function declares 2 variables, ``key``, ``alternate``:: +In the stored template you retrieve the arguments passed in the call using the ``arguments`` function. It both declares and initializes local variables, effectively parameters. The variables are positional; they get the value of the value given in the call in the same position. If the corresponding parameter is not provided in the call then ``arguments`` assigns that variable the provided default value. If there is no default value then the variable is set to the empty string. For example, the following ``arguments`` function declares 2 variables, ``key``, ``alternate``:: arguments(key, alternate='series') @@ -772,26 +528,18 @@ Examples, again assuming the stored template is named ``foo``: * ``foo('series', '#genre')`` the variable ``key`` is assigned the value ``series`` and the variable ``alternate`` is assigned the value ``#genre``. * ``foo()`` -- the variable ``key`` is assigned the empty string and the variable ``alternate`` is assigned the value ``#genre``. -An easy way to test stored templates is using the ``Template tester`` dialog. Give it a keyboard shortcut in -:guilabel:`Preferences->Advanced->Keyboard shortcuts->Template tester`. Giving the ``Stored templates`` dialog a -shortcut will help switching more rapidly between the tester and editing the stored template's source code. +An easy way to test stored templates is using the ``Template tester`` dialog. Give it a keyboard shortcut in :guilabel:`Preferences->Advanced->Keyboard shortcuts->Template tester`. Giving the ``Stored templates`` dialog a shortcut will help switching more rapidly between the tester and editing the stored template's source code. Providing additional information to templates ---------------------------------------------- -A developer can choose to pass additional information to the template processor, such as application-specific book -metadata or information about what the processor is being asked to do. A template can access this information -and use it during the evaluation. +A developer can choose to pass additional information to the template processor, such as application-specific book metadata or information about what the processor is being asked to do. A template can access this information and use it during the evaluation. **Developer: how to pass additional information** -The additional information is a Python dictionary containing pairs ``variable_name: variable_value`` where the values -must be strings. The template can access the dict, creating template local variables named ``variable_name`` -containing the value ``variable_value``. The user cannot change the name so it is best to use names that -won't collide with other template local variables, for example by prefixing the name with an underscore. +The additional information is a Python dictionary containing pairs ``variable_name: variable_value`` where the values must be strings. The template can access the dict, creating template local variables named ``variable_name`` containing the value ``variable_value``. The user cannot change the name so it is best to use names that won't collide with other template local variables, for example by prefixing the name with an underscore. -This dict is passed to the template processor (the ``formatter``) using the named parameter ``global_vars=your_dict``. -The full method signature is: +This dict is passed to the template processor (the ``formatter``) using the named parameter ``global_vars=your_dict``. The full method signature is: def safe_format(self, fmt, kwargs, error_value, book, column_name=None, template_cache=None, @@ -801,28 +549,23 @@ The full method signature is: **Template writer: how to access the additional information** -You access the additional information (the ``globals`` dict) in a template using the template function -``globals(id[=expression] [, id[=expression]]*)`` -where ``id`` is any legal variable name. This function checks whether the additional information provided -by the developer contains the name. If it does then the function assigns the provided value to a template -local variable with that name. If the name is not in the additional information and if an ``expression`` is -provided, the ``expression`` is evaluated and the result is assigned to the local variable. If neither -a value nor an expression is provided, the function assigns the empty string (``''``) to the local variable. +You access the additional information (the ``globals`` dict) in a template using the template function:: -A template can set a value in the ``globals`` dict using the template function -``set_globals(id[=expression] [, id[=expression]]*)``. This function sets the ``globals`` dict -key:value pair ``id:value`` where ``value`` is the value of the template local variable ``id``. If -that local variable doesn't exist then ``value`` is set to the result of evaluating ``expression``. + globals(id[=expression] [, id[=expression]]*) + +where ``id`` is any legal variable name. This function checks whether the additional information provided by the developer contains the name. If it does then the function assigns the provided value to a template local variable with that name. If the name is not in the additional information and if an ``expression`` is provided, the ``expression`` is evaluated and the result is assigned to the local variable. If neither a value nor an expression is provided, the function assigns the empty string (``''``) to the local variable. + +A template can set a value in the ``globals`` dict using the template function:: + + set_globals(id[=expression] [, id[=expression]]*) + +This function sets the ``globals`` dict key:value pair ``id:value`` where ``value`` is the value of the template local variable ``id``. If that local variable doesn't exist then ``value`` is set to the result of evaluating ``expression``. Notes on the difference between modes ----------------------------------------- -The three program modes, :ref:`Single Function Mode ` (SFM), :ref:`Template Program Mode ` -(TPM), and :ref:`General Program Mode ` (GPM), work differently. SFM is intended to be 'simple' so -it hides a lot of programming language bits. For example, the value of the column is always passed as -an 'invisible' first argument to a function included in the template. SFM also doesn't support the difference -between variables and strings; all values are strings. +The three program modes, :ref:`Single Function Mode ` (SFM), :ref:`Template Program Mode ` (TPM), and :ref:`General Program Mode ` (GPM), work differently. SFM is intended to be 'simple' so it hides a lot of programming language bits. For example, the value of the column is always passed as an 'invisible' first argument to a function included in the template. SFM also doesn't support the difference between variables and strings; all values are strings. Example: the following SFM template returns either the series name or the string "no series":: @@ -830,86 +573,63 @@ Example: the following SFM template returns either the series name or the string The equivalent template in TPM is :: - ``{series:'ifempty($, 'no series')'}`` + {series:'ifempty($, 'no series')'} The equivalent template in GPM is:: - ``program: ifempty(field('series'), 'no series')`` + program: ifempty(field('series'), 'no series') -The first argument to ``ifempty`` is the value of the field ``series``. The second argument -is the string ``no series``. In SFM the first argument, the value of the field, -is automatically passed (the invisible argument). +The first argument to ``ifempty`` is the value of the field ``series``. The second argument is the string ``no series``. In SFM the first argument, the value of the field, is automatically passed (the invisible argument). -Several template functions, for example ``booksize()`` and ``current_library_name()``, take no arguments. -Because of the 'invisible argument' you cannot use these functions in SFM. +Several template functions, for example ``booksize()`` and ``current_library_name()``, take no arguments. Because of the 'invisible argument' you cannot use these functions in SFM. -Nested functions, where a function calls another function to compute an argument, cannot be used in SFM. -For example this template, intended to return the first 5 characters of the series value uppercased, won't work in SFM:: +Nested functions, where a function calls another function to compute an argument, cannot be used in SFM. For example this template, intended to return the first 5 characters of the series value uppercased, won't work in SFM:: - ``{series:uppercase(substr(0,5))}`` + {series:uppercase(substr(0,5))} TPM and GPM support nested functions. The above template in TPM would be:: - ``{series:'uppercase(substr($, 0,5))'}`` + {series:'uppercase(substr($, 0,5))'} In GPM it would be:: - ``program: uppercase(substr(field('series'), 0,5))`` + program: uppercase(substr(field('series'), 0,5)) User-defined Python template functions ------------------------------------------ -You can add your own Python functions to the template processor. Such functions can be used in any of the three -template programming modes. The functions are added by going to -:guilabel:`Preferences -> Advanced -> Template functions`. Instructions are shown in that dialog. +You can add your own Python functions to the template processor. Such functions can be used in any of the three template programming modes. The functions are added by going to :guilabel:`Preferences -> Advanced -> Template functions`. Instructions are shown in that dialog. Special notes for save/send templates --------------------------------------- -Special processing is applied when a template is used in a `save to disk` or `send to device` template. The -values of the fields are cleaned, replacing characters that are special to file systems with underscores, -including slashes. This means that field text cannot be used to create folders. However, slashes are not -changed in prefix or suffix strings, so slashes in these strings will cause folders to be created. -Because of this, you can create variable-depth folder structure. +Special processing is applied when a template is used in a `save to disk` or `send to device` template. The values of the fields are cleaned, replacing characters that are special to file systems with underscores, including slashes. This means that field text cannot be used to create folders. However, slashes are not changed in prefix or suffix strings, so slashes in these strings will cause folders to be created. Because of this, you can create variable-depth folder structure. -For example, assume we want the folder structure `series/series_index - title`, with the caveat that if -series does not exist, then the title should be in the top folder. The template to do this is:: +For example, assume we want the folder structure `series/series_index - title`, with the caveat that if series does not exist, then the title should be in the top folder. The template to do this is:: {series:||/}{series_index:|| - }{title} The slash and the hyphen appear only if series is not empty. -The lookup function lets us do even fancier processing. For example, assume that if a book has a series, -then we want the folder structure `series/series index - title.fmt`. If the book does not have a series -then we want the folder structure `genre/author_sort/title.fmt`. If the book has no genre then we want to -use 'Unknown'. We want two completely different paths, depending on the value of series. +The lookup function lets us do even fancier processing. For example, assume that if a book has a series, then we want the folder structure `series/series index - title.fmt`. If the book does not have a series then we want the folder structure `genre/author_sort/title.fmt`. If the book has no genre then we want to use 'Unknown'. We want two completely different paths, depending on the value of series. To accomplish this, we: - 1. Create a composite field (give it lookup name #AA) containing ``{series}/{series_index} - {title}``. If + 1. Create a composite field (give it lookup name #aa) containing ``{series}/{series_index} - {title}``. If the series is not empty, then this template will produce `series/series_index - title`. - 2. Create a composite field (give it lookup name #BB) containing ``{#genre:ifempty(Unknown)}/{author_sort}/{title}``. + 2. Create a composite field (give it lookup name #bb) containing ``{#genre:ifempty(Unknown)}/{author_sort}/{title}``. This template produces `genre/author_sort/title`, where an empty genre is replaced with `Unknown`. - 3. Set the save template to ``{series:lookup(.,#AA,#BB)}``. This template chooses composite field #AA if series is not empty, - and composite field #BB if series is empty. We therefore have two completely different save paths, depending on whether or not `series` is empty. + 3. Set the save template to ``{series:lookup(.,#aa,#bb}``. This template chooses composite field ``#aa`` if series is not empty and composite field ``#bb`` if series is empty. We therefore have two completely different save paths, depending on whether or not `series` is empty. Templates and plugboards --------------------------- -Plugboards are used for changing the metadata written into books during send-to-device and save-to-disk operations. -A plugboard permits you to specify a template to provide the data to write into the book's metadata. You can use -plugboards to modify the following fields: authors, author_sort, language, publisher, tags, title, title_sort. This -feature helps people who want to use different metadata in books on devices to solve sorting or display issues. +Plugboards are used for changing the metadata written into books during send-to-device and save-to-disk operations. A plugboard permits you to specify a template to provide the data to write into the book's metadata. You can use plugboards to modify the following fields: authors, author_sort, language, publisher, tags, title, title_sort. This feature helps people who want to use different metadata in books on devices to solve sorting or display issues. -When you create a plugboard, you specify the format and device for which the plugboard is to be used. A -special device is provided, ``save_to_disk``, that is used when saving formats (as opposed to sending them to a -device). Once you have chosen the format and device, you choose the metadata fields to change, providing -templates to supply the new values. These templates are `connected` to their destination fields, hence the name -`plugboards`. You can, of course, use composite columns in these templates. +When you create a plugboard, you specify the format and device for which the plugboard is to be used. A special device is provided, ``save_to_disk``, that is used when saving formats (as opposed to sending them to a device). Once you have chosen the format and device, you choose the metadata fields to change, providing templates to supply the new values. These templates are `connected` to their destination fields, hence the name `plugboards`. You can of course use composite columns in these templates. When a plugboard might apply (Content server, save to disk, or send to device), calibre searches the -defined plugboards to choose the correct one for the given format and device. For example, to find the -appropriate plugboard for an EPUB book being sent to an ANDROID device, calibre searches +defined plugboards to choose the correct one for the given format and device. For example, to find the appropriate plugboard for an EPUB book being sent to an ANDROID device, calibre searches the plugboards using the following search order: * a plugboard with an exact match on format and device, e.g., ``EPUB`` and ``ANDROID`` @@ -917,34 +637,20 @@ the plugboards using the following search order: * a plugboard with the special ``any format`` choice and an exact match on device, e.g., ``any format`` and ``ANDROID`` * a plugboard with ``any format`` and ``any device`` -The tags and authors fields have special treatment, because both of these fields can hold more than one item. -A book can have many tags and many authors. When you specify that one of these two fields is to be changed, -the template's result is examined to see if more than one item is there. -For tags, the result is cut apart wherever calibre finds a comma. For example, if the template produces -the value ``Thriller, Horror``, then the result will be two tags, ``Thriller`` and ``Horror``. There is no way -to put a comma in the middle of a tag. +The tags and authors fields have special treatment, because both of these fields can hold more than one item. A book can have many tags and many authors. When you specify that one of these two fields is to be changed, the template's result is examined to see if more than one item is there. For tags, the result is cut apart wherever calibre finds a comma. For example, if the template produces +the value ``Thriller, Horror``, then the result will be two tags, ``Thriller`` and ``Horror``. There is no way to put a comma in the middle of a tag. -The same thing happens for authors, but using a different character for the cut, a `&` (ampersand) instead of -a comma. For example, if the template produces the value ``Blogs, Joe&Posts, Susan``, then the book will -end up with two authors, ``Blogs, Joe`` and ``Posts, Susan``. If the template produces the -value ``Blogs, Joe;Posts, Susan``, then the book will have one author with a rather strange name. +The same thing happens for authors, but using a different character for the cut, a `&` (ampersand) instead of a comma. For example, if the template produces the value ``Blogs, Joe&Posts, Susan``, then the book will end up with two authors, ``Blogs, Joe`` and ``Posts, Susan``. If the template produces the value ``Blogs, Joe;Posts, Susan``, then the book will have one author with a rather strange name. -Plugboards affect the metadata written into the book when it is saved to disk or written to the device. -Plugboards do not affect the metadata used by ``save to disk`` and ``send to device`` to create the file names. -Instead, file names are constructed using the templates entered on the appropriate -preferences window. +Plugboards affect the metadata written into the book when it is saved to disk or written to the device. Plugboards do not affect the metadata used by ``save to disk`` and ``send to device`` to create the file names. Instead, file names are constructed using the templates entered on the appropriate preferences window. -Tips +Tips: ------------ -You might find the following tips useful. - * Use the Template Tester to test templates. Add the tester to the context menu for books in the library and/or give it a keyboard shortcut. - * Templates can use other templates by referencing composite columns built with the desired template. - Alternatively, you could use Stored Templates. - * In a plugboard, you can set a field to empty (or whatever is equivalent to empty) by using the special template ``{}``. - This template will always evaluate to an empty string. + * Templates can use other templates by referencing composite columns built with the desired template. Alternatively, you can use Stored Templates. + * In a plugboard, you can set a field to empty (or whatever is equivalent to empty) by using the special template ``{}``. This template will always evaluate to an empty string. * The technique described above to show numbers even if they have a zero value works with the standard field series_index. .. _template_functions_reference: