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Help/command/list.rst

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list

Operations on :ref:semicolon-separated lists <CMake Language Lists>.

Synopsis ^^^^^^^^

.. parsed-literal::

Reading_ list(LENGTH_ <list> <out-var>) list(GET_ <list> <element index> [<index> ...] <out-var>) list(JOIN_ <list> <glue> <out-var>) list(SUBLIST_ <list> <begin> <length> <out-var>)

Search_ list(FIND_ <list> <value> <out-var>)

Modification_ list(APPEND_ <list> [<element>...]) list(FILTER_ <list> {INCLUDE | EXCLUDE} REGEX <regex>) list(INSERT_ <list> <index> [<element>...]) list(POP_BACK_ <list> [<out-var>...]) list(POP_FRONT_ <list> [<out-var>...]) list(PREPEND_ <list> [<element>...]) list(REMOVE_ITEM_ <list> <value>...) list(REMOVE_AT_ <list> <index>...) list(REMOVE_DUPLICATES_ <list>) list(TRANSFORM_ <list> <ACTION> [...])

Ordering_ list(REVERSE_ <list>) list(SORT_ <list> [...])

Introduction ^^^^^^^^^^^^

The list subcommands :cref:APPEND, :cref:INSERT, :cref:FILTER, :cref:PREPEND, :cref:POP_BACK, :cref:POP_FRONT, :cref:REMOVE_AT, :cref:REMOVE_ITEM, :cref:REMOVE_DUPLICATES, :cref:REVERSE and :cref:SORT may create new values for the list within the current CMake variable scope. Similar to the :command:set command, the list command creates new variable values in the current scope, even if the list itself is actually defined in a parent scope. To propagate the results of these operations upwards, use :command:set with PARENT_SCOPE, :command:set with CACHE INTERNAL, or some other means of value propagation.

.. note::

A list in cmake is a ; separated group of strings. To create a list, the :command:set command can be used. For example, set(var a b c d e) creates a list with a;b;c;d;e, and set(var "a b c d e") creates a string or a list with one item in it. (Note that macro arguments are not variables, and therefore cannot be used in LIST commands.)

Individual elements may not contain an unequal number of [ and ] characters, and may not end in a backslash (\). See :ref:semicolon-separated lists <CMake Language Lists> for details.

.. note::

When specifying index values, if <element index> is 0 or greater, it is indexed from the beginning of the list, with 0 representing the first list element. If <element index> is -1 or lesser, it is indexed from the end of the list, with -1 representing the last list element. Be careful when counting with negative indices: they do not start from 0. -0 is equivalent to 0, the first list element.

Reading ^^^^^^^

.. signature:: list(LENGTH <list> <output variable>)

Returns the list's length.

.. signature:: list(GET <list> <element index> [<element index> ...] <output variable>)

Returns the list of elements specified by indices from the list.

.. signature:: list(JOIN <list> <glue> <output variable>)

.. versionadded:: 3.12

Returns a string joining all list's elements using the glue string. To join multiple strings, which are not part of a list, use :command:string(JOIN).

.. signature:: list(SUBLIST <list> <begin> <length> <output variable>)

.. versionadded:: 3.12

Returns a sublist of the given list. If <length> is 0, an empty list will be returned. If <length> is -1 or the list is smaller than <begin>+<length> then the remaining elements of the list starting at <begin> will be returned.

Search ^^^^^^

.. signature:: list(FIND <list> <value> <output variable>)

Returns the index of the element specified in the list or -1 if it wasn't found.

Modification ^^^^^^^^^^^^

.. signature:: list(APPEND <list> [<element> ...])

Appends elements to the list. If no variable named <list> exists in the current scope its value is treated as empty and the elements are appended to that empty list.

.. signature:: list(FILTER <list> <INCLUDE|EXCLUDE> REGEX <regular_expression>)

.. versionadded:: 3.6

Includes or removes items from the list that match the mode's pattern. In REGEX mode, items will be matched against the given regular expression.

For more information on regular expressions look under :ref:string(REGEX) <Regex Specification>.

.. signature:: list(INSERT <list> <element_index> <element> [<element> ...])

Inserts elements to the list to the specified index. It is an error to specify an out-of-range index. Valid indexes are 0 to N where N is the length of the list, inclusive. An empty list has length 0. If no variable named <list> exists in the current scope its value is treated as empty and the elements are inserted in that empty list.

.. signature:: list(POP_BACK <list> [<out-var>...])

.. versionadded:: 3.15

If no variable name is given, removes exactly one element. Otherwise, with N variable names provided, assign the last N elements' values to the given variables and then remove the last N values from <list>.

.. signature:: list(POP_FRONT <list> [<out-var>...])

.. versionadded:: 3.15

If no variable name is given, removes exactly one element. Otherwise, with N variable names provided, assign the first N elements' values to the given variables and then remove the first N values from <list>.

.. signature:: list(PREPEND <list> [<element> ...])

.. versionadded:: 3.15

Insert elements to the 0th position in the list. If no variable named <list> exists in the current scope its value is treated as empty and the elements are prepended to that empty list.

.. signature:: list(REMOVE_ITEM <list> <value> [<value> ...])

Removes all instances of the given items from the list.

.. signature:: list(REMOVE_AT <list> <index> [<index> ...])

Removes items at given indices from the list.

.. signature:: list(REMOVE_DUPLICATES <list>)

Removes duplicated items in the list. The relative order of items is preserved, but if duplicates are encountered, only the first instance is preserved.

.. signature:: list(TRANSFORM <list> <ACTION> [<SELECTOR>] [OUTPUT_VARIABLE <output variable>])

.. versionadded:: 3.12

Transforms the list by applying an <ACTION> to all or, by specifying a <SELECTOR>, to the selected elements of the list, storing the result in-place or in the specified output variable.

.. note::

The ``TRANSFORM`` sub-command does not change the number of elements in the
list. If a ``<SELECTOR>`` is specified, only some elements will be changed,
the other ones will remain the same as before the transformation.

<ACTION> specifies the action to apply to the elements of the list. The actions have exactly the same semantics as sub-commands of the :command:string command. <ACTION> must be one of the following:

:command:`APPEND <string(APPEND)>`, :command:`PREPEND <string(PREPEND)>`
  Append, prepend specified value to each element of the list.

  .. signature::
    list(TRANSFORM <list> (APPEND|PREPEND) <value> ...)
    :target: TRANSFORM_APPEND

:command:`TOLOWER <string(TOLOWER)>`, :command:`TOUPPER <string(TOUPPER)>`
  Convert each element of the list to lower, upper characters.

  .. signature::
    list(TRANSFORM <list> (TOLOWER|TOUPPER) ...)
    :target: TRANSFORM_TOLOWER

:command:`STRIP <string(STRIP)>`
  Remove leading and trailing spaces from each element of the list.

  .. signature::
    list(TRANSFORM <list> STRIP ...)
    :target: TRANSFORM_STRIP

:command:`GENEX_STRIP <string(GENEX_STRIP)>`
  Strip any
  :manual:`generator expressions <cmake-generator-expressions(7)>`
  from each element of the list.

  .. signature::
    list(TRANSFORM <list> GENEX_STRIP ...)
    :target: TRANSFORM_GENEX_STRIP

:command:`REPLACE <string(REGEX REPLACE)>`
  Match the regular expression as many times as possible and substitute
  the replacement expression for the match for each element of the list
  (same semantic as :command:`string(REGEX REPLACE)`).

  .. signature::
    list(TRANSFORM <list> REPLACE <regular_expression>
                                  <replace_expression> ...)
    :target: TRANSFORM_REPLACE

  .. versionchanged:: 4.1
    The ``^`` anchor now matches only at the beginning of the input
    element instead of the beginning of each repeated search.
    See policy :policy:`CMP0186`.

<SELECTOR> determines which elements of the list will be transformed. Only one type of selector can be specified at a time. When given, <SELECTOR> must be one of the following:

``AT``
  Specify a list of indexes.

  .. code-block:: cmake

    list(TRANSFORM <list> <ACTION> AT <index> [<index> ...] ...)

``FOR``
  Specify a range with, optionally,
  an increment used to iterate over the range.

  .. code-block:: cmake

    list(TRANSFORM <list> <ACTION> FOR <start> <stop> [<step>] ...)

``REGEX``
  Specify a regular expression.
  Only elements matching the regular expression will be transformed.

  .. code-block:: cmake

    list(TRANSFORM <list> <ACTION> REGEX <regular_expression> ...)

Ordering ^^^^^^^^

.. signature:: list(REVERSE <list>)

Reverses the contents of the list in-place.

.. signature:: list(SORT <list> [COMPARE <compare>] [CASE <case>] [ORDER <order>])

Sorts the list in-place alphabetically.

.. versionadded:: 3.13 Added the COMPARE, CASE, and ORDER options.

.. versionadded:: 3.18 Added the COMPARE NATURAL option.

Use the COMPARE keyword to select the comparison method for sorting. The <compare> option should be one of:

``STRING``
  Sorts a list of strings alphabetically.
  This is the default behavior if the ``COMPARE`` option is not given.

``FILE_BASENAME``
  Sorts a list of pathnames of files by their basenames.

``NATURAL``
  Sorts a list of strings using natural order
  (see ``strverscmp(3)`` manual), i.e. such that contiguous digits
  are compared as whole numbers.
  For example: the following list *10.0 1.1 2.1 8.0 2.0 3.1*
  will be sorted as *1.1 2.0 2.1 3.1 8.0 10.0* if the ``NATURAL``
  comparison is selected where it will be sorted as
  *1.1 10.0 2.0 2.1 3.1 8.0* with the ``STRING`` comparison.

Use the CASE keyword to select a case sensitive or case insensitive sort mode. The <case> option should be one of:

``SENSITIVE``
  List items are sorted in a case-sensitive manner.
  This is the default behavior if the ``CASE`` option is not given.

``INSENSITIVE``
  List items are sorted case insensitively.  The order of
  items which differ only by upper/lowercase is not specified.

To control the sort order, the ORDER keyword can be given. The <order> option should be one of:

``ASCENDING``
  Sorts the list in ascending order.
  This is the default behavior when the ``ORDER`` option is not given.

``DESCENDING``
  Sorts the list in descending order.