CMake/Help/command/string.rst
Antons Jeļkins aafa392c12 string(TIMESTAMP): Add %V specifier for ISO 8601 week number
In ISO 8601 weeks begin with Monday. The first week of
the year is the week which contains the first Thursday
of the year.
2021-08-02 16:31:53 +02:00

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ReStructuredText

string
------
String operations.
Synopsis
^^^^^^^^
.. parsed-literal::
`Search and Replace`_
string(`FIND`_ <string> <substring> <out-var> [...])
string(`REPLACE`_ <match-string> <replace-string> <out-var> <input>...)
string(`REGEX MATCH`_ <match-regex> <out-var> <input>...)
string(`REGEX MATCHALL`_ <match-regex> <out-var> <input>...)
string(`REGEX REPLACE`_ <match-regex> <replace-expr> <out-var> <input>...)
`Manipulation`_
string(`APPEND`_ <string-var> [<input>...])
string(`PREPEND`_ <string-var> [<input>...])
string(`CONCAT`_ <out-var> [<input>...])
string(`JOIN`_ <glue> <out-var> [<input>...])
string(`TOLOWER`_ <string> <out-var>)
string(`TOUPPER`_ <string> <out-var>)
string(`LENGTH`_ <string> <out-var>)
string(`SUBSTRING`_ <string> <begin> <length> <out-var>)
string(`STRIP`_ <string> <out-var>)
string(`GENEX_STRIP`_ <string> <out-var>)
string(`REPEAT`_ <string> <count> <out-var>)
`Comparison`_
string(`COMPARE`_ <op> <string1> <string2> <out-var>)
`Hashing`_
string(`\<HASH\> <HASH_>`_ <out-var> <input>)
`Generation`_
string(`ASCII`_ <number>... <out-var>)
string(`HEX`_ <string> <out-var>)
string(`CONFIGURE`_ <string> <out-var> [...])
string(`MAKE_C_IDENTIFIER`_ <string> <out-var>)
string(`RANDOM`_ [<option>...] <out-var>)
string(`TIMESTAMP`_ <out-var> [<format string>] [UTC])
string(`UUID`_ <out-var> ...)
`JSON`_
string(JSON <out-var> [ERROR_VARIABLE <error-var>]
{`GET`_ | `TYPE`_ | :ref:`LENGTH <JSONLENGTH>` | `REMOVE`_}
<json-string> <member|index> [<member|index> ...])
string(JSON <out-var> [ERROR_VARIABLE <error-var>]
`MEMBER`_ <json-string>
[<member|index> ...] <index>)
string(JSON <out-var> [ERROR_VARIABLE <error-var>]
`SET`_ <json-string>
<member|index> [<member|index> ...] <value>)
string(JSON <out-var> [ERROR_VARIABLE <error-var>]
`EQUAL`_ <json-string1> <json-string2>)
Search and Replace
^^^^^^^^^^^^^^^^^^
Search and Replace With Plain Strings
"""""""""""""""""""""""""""""""""""""
.. _FIND:
.. code-block:: cmake
string(FIND <string> <substring> <output_variable> [REVERSE])
Return the position where the given ``<substring>`` was found in
the supplied ``<string>``. If the ``REVERSE`` flag was used, the command will
search for the position of the last occurrence of the specified
``<substring>``. If the ``<substring>`` is not found, a position of -1 is
returned.
The ``string(FIND)`` subcommand treats all strings as ASCII-only characters.
The index stored in ``<output_variable>`` will also be counted in bytes,
so strings containing multi-byte characters may lead to unexpected results.
.. _REPLACE:
.. code-block:: cmake
string(REPLACE <match_string>
<replace_string> <output_variable>
<input> [<input>...])
Replace all occurrences of ``<match_string>`` in the ``<input>``
with ``<replace_string>`` and store the result in the ``<output_variable>``.
Search and Replace With Regular Expressions
"""""""""""""""""""""""""""""""""""""""""""
.. _`REGEX MATCH`:
.. code-block:: cmake
string(REGEX MATCH <regular_expression>
<output_variable> <input> [<input>...])
Match the ``<regular_expression>`` once and store the match in the
``<output_variable>``.
All ``<input>`` arguments are concatenated before matching.
Regular expressions are specified in the subsection just below.
.. _`REGEX MATCHALL`:
.. code-block:: cmake
string(REGEX MATCHALL <regular_expression>
<output_variable> <input> [<input>...])
Match the ``<regular_expression>`` as many times as possible and store the
matches in the ``<output_variable>`` as a list.
All ``<input>`` arguments are concatenated before matching.
.. _`REGEX REPLACE`:
.. code-block:: cmake
string(REGEX REPLACE <regular_expression>
<replacement_expression> <output_variable>
<input> [<input>...])
Match the ``<regular_expression>`` as many times as possible and substitute
the ``<replacement_expression>`` for the match in the output.
All ``<input>`` arguments are concatenated before matching.
The ``<replacement_expression>`` may refer to parenthesis-delimited
subexpressions of the match using ``\1``, ``\2``, ..., ``\9``. Note that
two backslashes (``\\1``) are required in CMake code to get a backslash
through argument parsing.
.. _`Regex Specification`:
Regex Specification
"""""""""""""""""""
The following characters have special meaning in regular expressions:
``^``
Matches at beginning of input
``$``
Matches at end of input
``.``
Matches any single character
``\<char>``
Matches the single character specified by ``<char>``. Use this to
match special regex characters, e.g. ``\.`` for a literal ``.``
or ``\\`` for a literal backslash ``\``. Escaping a non-special
character is unnecessary but allowed, e.g. ``\a`` matches ``a``.
``[ ]``
Matches any character(s) inside the brackets
``[^ ]``
Matches any character(s) not inside the brackets
``-``
Inside brackets, specifies an inclusive range between
characters on either side e.g. ``[a-f]`` is ``[abcdef]``
To match a literal ``-`` using brackets, make it the first
or the last character e.g. ``[+*/-]`` matches basic
mathematical operators.
``*``
Matches preceding pattern zero or more times
``+``
Matches preceding pattern one or more times
``?``
Matches preceding pattern zero or once only
``|``
Matches a pattern on either side of the ``|``
``()``
Saves a matched subexpression, which can be referenced
in the ``REGEX REPLACE`` operation.
.. versionadded:: 3.9
All regular expression-related commands, including e.g.
:command:`if(MATCHES)`, save subgroup matches in the variables
:variable:`CMAKE_MATCH_<n>` for ``<n>`` 0..9.
``*``, ``+`` and ``?`` have higher precedence than concatenation. ``|``
has lower precedence than concatenation. This means that the regular
expression ``^ab+d$`` matches ``abbd`` but not ``ababd``, and the regular
expression ``^(ab|cd)$`` matches ``ab`` but not ``abd``.
CMake language :ref:`Escape Sequences` such as ``\t``, ``\r``, ``\n``,
and ``\\`` may be used to construct literal tabs, carriage returns,
newlines, and backslashes (respectively) to pass in a regex. For example:
* The quoted argument ``"[ \t\r\n]"`` specifies a regex that matches
any single whitespace character.
* The quoted argument ``"[/\\]"`` specifies a regex that matches
a single forward slash ``/`` or backslash ``\``.
* The quoted argument ``"[A-Za-z0-9_]"`` specifies a regex that matches
any single "word" character in the C locale.
* The quoted argument ``"\\(\\a\\+b\\)"`` specifies a regex that matches
the exact string ``(a+b)``. Each ``\\`` is parsed in a quoted argument
as just ``\``, so the regex itself is actually ``\(\a\+\b\)``. This
can alternatively be specified in a :ref:`bracket argument` without
having to escape the backslashes, e.g. ``[[\(\a\+\b\)]]``.
Manipulation
^^^^^^^^^^^^
.. _APPEND:
.. code-block:: cmake
string(APPEND <string_variable> [<input>...])
.. versionadded:: 3.4
Append all the ``<input>`` arguments to the string.
.. _PREPEND:
.. code-block:: cmake
string(PREPEND <string_variable> [<input>...])
.. versionadded:: 3.10
Prepend all the ``<input>`` arguments to the string.
.. _CONCAT:
.. code-block:: cmake
string(CONCAT <output_variable> [<input>...])
Concatenate all the ``<input>`` arguments together and store
the result in the named ``<output_variable>``.
.. _JOIN:
.. code-block:: cmake
string(JOIN <glue> <output_variable> [<input>...])
.. versionadded:: 3.12
Join all the ``<input>`` arguments together using the ``<glue>``
string and store the result in the named ``<output_variable>``.
To join a list's elements, prefer to use the ``JOIN`` operator
from the :command:`list` command. This allows for the elements to have
special characters like ``;`` in them.
.. _TOLOWER:
.. code-block:: cmake
string(TOLOWER <string> <output_variable>)
Convert ``<string>`` to lower characters.
.. _TOUPPER:
.. code-block:: cmake
string(TOUPPER <string> <output_variable>)
Convert ``<string>`` to upper characters.
.. _LENGTH:
.. code-block:: cmake
string(LENGTH <string> <output_variable>)
Store in an ``<output_variable>`` a given string's length in bytes.
Note that this means if ``<string>`` contains multi-byte characters, the
result stored in ``<output_variable>`` will *not* be the number of characters.
.. _SUBSTRING:
.. code-block:: cmake
string(SUBSTRING <string> <begin> <length> <output_variable>)
Store in an ``<output_variable>`` a substring of a given ``<string>``. If
``<length>`` is ``-1`` the remainder of the string starting at ``<begin>``
will be returned.
.. versionchanged:: 3.2
If ``<string>`` is shorter than ``<length>`` then the end of the string
is used instead. Previous versions of CMake reported an error in this case.
Both ``<begin>`` and ``<length>`` are counted in bytes, so care must
be exercised if ``<string>`` could contain multi-byte characters.
.. _STRIP:
.. code-block:: cmake
string(STRIP <string> <output_variable>)
Store in an ``<output_variable>`` a substring of a given ``<string>`` with
leading and trailing spaces removed.
.. _GENEX_STRIP:
.. code-block:: cmake
string(GENEX_STRIP <string> <output_variable>)
.. versionadded:: 3.1
Strip any :manual:`generator expressions <cmake-generator-expressions(7)>`
from the input ``<string>`` and store the result in the ``<output_variable>``.
.. _REPEAT:
.. code-block:: cmake
string(REPEAT <string> <count> <output_variable>)
.. versionadded:: 3.15
Produce the output string as the input ``<string>`` repeated ``<count>`` times.
Comparison
^^^^^^^^^^
.. _COMPARE:
.. code-block:: cmake
string(COMPARE LESS <string1> <string2> <output_variable>)
string(COMPARE GREATER <string1> <string2> <output_variable>)
string(COMPARE EQUAL <string1> <string2> <output_variable>)
string(COMPARE NOTEQUAL <string1> <string2> <output_variable>)
string(COMPARE LESS_EQUAL <string1> <string2> <output_variable>)
string(COMPARE GREATER_EQUAL <string1> <string2> <output_variable>)
Compare the strings and store true or false in the ``<output_variable>``.
.. versionadded:: 3.7
Added the ``LESS_EQUAL`` and ``GREATER_EQUAL`` options.
.. _`Supported Hash Algorithms`:
Hashing
^^^^^^^
.. _`HASH`:
.. code-block:: cmake
string(<HASH> <output_variable> <input>)
Compute a cryptographic hash of the ``<input>`` string.
The supported ``<HASH>`` algorithm names are:
``MD5``
Message-Digest Algorithm 5, RFC 1321.
``SHA1``
US Secure Hash Algorithm 1, RFC 3174.
``SHA224``
US Secure Hash Algorithms, RFC 4634.
``SHA256``
US Secure Hash Algorithms, RFC 4634.
``SHA384``
US Secure Hash Algorithms, RFC 4634.
``SHA512``
US Secure Hash Algorithms, RFC 4634.
``SHA3_224``
Keccak SHA-3.
``SHA3_256``
Keccak SHA-3.
``SHA3_384``
Keccak SHA-3.
``SHA3_512``
Keccak SHA-3.
.. versionadded:: 3.8
Added the ``SHA3_*`` hash algorithms.
Generation
^^^^^^^^^^
.. _ASCII:
.. code-block:: cmake
string(ASCII <number> [<number> ...] <output_variable>)
Convert all numbers into corresponding ASCII characters.
.. _HEX:
.. code-block:: cmake
string(HEX <string> <output_variable>)
.. versionadded:: 3.18
Convert each byte in the input ``<string>`` to its hexadecimal representation
and store the concatenated hex digits in the ``<output_variable>``. Letters in
the output (``a`` through ``f``) are in lowercase.
.. _CONFIGURE:
.. code-block:: cmake
string(CONFIGURE <string> <output_variable>
[@ONLY] [ESCAPE_QUOTES])
Transform a ``<string>`` like :command:`configure_file` transforms a file.
.. _MAKE_C_IDENTIFIER:
.. code-block:: cmake
string(MAKE_C_IDENTIFIER <string> <output_variable>)
Convert each non-alphanumeric character in the input ``<string>`` to an
underscore and store the result in the ``<output_variable>``. If the first
character of the ``<string>`` is a digit, an underscore will also be prepended
to the result.
.. _RANDOM:
.. code-block:: cmake
string(RANDOM [LENGTH <length>] [ALPHABET <alphabet>]
[RANDOM_SEED <seed>] <output_variable>)
Return a random string of given ``<length>`` consisting of
characters from the given ``<alphabet>``. Default length is 5 characters
and default alphabet is all numbers and upper and lower case letters.
If an integer ``RANDOM_SEED`` is given, its value will be used to seed the
random number generator.
.. _TIMESTAMP:
.. code-block:: cmake
string(TIMESTAMP <output_variable> [<format_string>] [UTC])
Write a string representation of the current date
and/or time to the ``<output_variable>``.
If the command is unable to obtain a timestamp, the ``<output_variable>``
will be set to the empty string ``""``.
The optional ``UTC`` flag requests the current date/time representation to
be in Coordinated Universal Time (UTC) rather than local time.
The optional ``<format_string>`` may contain the following format
specifiers:
``%%``
.. versionadded:: 3.8
A literal percent sign (%).
``%d``
The day of the current month (01-31).
``%H``
The hour on a 24-hour clock (00-23).
``%I``
The hour on a 12-hour clock (01-12).
``%j``
The day of the current year (001-366).
``%m``
The month of the current year (01-12).
``%b``
.. versionadded:: 3.7
Abbreviated month name (e.g. Oct).
``%B``
.. versionadded:: 3.10
Full month name (e.g. October).
``%M``
The minute of the current hour (00-59).
``%s``
.. versionadded:: 3.6
Seconds since midnight (UTC) 1-Jan-1970 (UNIX time).
``%S``
The second of the current minute. 60 represents a leap second. (00-60)
``%U``
The week number of the current year (00-53).
``%V``
.. versionadded:: 3.22
The ISO 8601 week number of the current year (01-53).
``%w``
The day of the current week. 0 is Sunday. (0-6)
``%a``
.. versionadded:: 3.7
Abbreviated weekday name (e.g. Fri).
``%A``
.. versionadded:: 3.10
Full weekday name (e.g. Friday).
``%y``
The last two digits of the current year (00-99).
``%Y``
The current year.
Unknown format specifiers will be ignored and copied to the output
as-is.
If no explicit ``<format_string>`` is given, it will default to:
::
%Y-%m-%dT%H:%M:%S for local time.
%Y-%m-%dT%H:%M:%SZ for UTC.
.. versionadded:: 3.8
If the ``SOURCE_DATE_EPOCH`` environment variable is set,
its value will be used instead of the current time.
See https://reproducible-builds.org/specs/source-date-epoch/ for details.
.. _UUID:
.. code-block:: cmake
string(UUID <output_variable> NAMESPACE <namespace> NAME <name>
TYPE <MD5|SHA1> [UPPER])
.. versionadded:: 3.1
Create a universally unique identifier (aka GUID) as per RFC4122
based on the hash of the combined values of ``<namespace>``
(which itself has to be a valid UUID) and ``<name>``.
The hash algorithm can be either ``MD5`` (Version 3 UUID) or
``SHA1`` (Version 5 UUID).
A UUID has the format ``xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx``
where each ``x`` represents a lower case hexadecimal character.
Where required, an uppercase representation can be requested
with the optional ``UPPER`` flag.
.. _JSON:
JSON
^^^^
.. versionadded:: 3.19
Functionality for querying a JSON string.
.. note::
In each of the following JSON-related subcommands, if the optional
``ERROR_VARIABLE`` argument is given, errors will be reported in
``<error-variable>`` and the ``<out-var>`` will be set to
``<member|index>-[<member|index>...]-NOTFOUND`` with the path elements
up to the point where the error occurred, or just ``NOTFOUND`` if there
is no relevant path. If an error occurs but the ``ERROR_VARIABLE``
option is not present, a fatal error message is generated. If no error
occurs, the ``<error-variable>`` will be set to ``NOTFOUND``.
.. _GET:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-variable>]
GET <json-string> <member|index> [<member|index> ...])
Get an element from ``<json-string>`` at the location given
by the list of ``<member|index>`` arguments.
Array and object elements will be returned as a JSON string.
Boolean elements will be returned as ``ON`` or ``OFF``.
Null elements will be returned as an empty string.
Number and string types will be returned as strings.
.. _TYPE:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-variable>]
TYPE <json-string> <member|index> [<member|index> ...])
Get the type of an element in ``<json-string>`` at the location
given by the list of ``<member|index>`` arguments. The ``<out-var>``
will be set to one of ``NULL``, ``NUMBER``, ``STRING``, ``BOOLEAN``,
``ARRAY``, or ``OBJECT``.
.. _MEMBER:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-var>]
MEMBER <json-string>
[<member|index> ...] <index>)
Get the name of the ``<index>``-th member in ``<json-string>`` at the location
given by the list of ``<member|index>`` arguments.
Requires an element of object type.
.. _JSONLENGTH:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-variable>]
LENGTH <json-string> <member|index> [<member|index> ...])
Get the length of an element in ``<json-string>`` at the location
given by the list of ``<member|index>`` arguments.
Requires an element of array or object type.
.. _REMOVE:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-variable>]
REMOVE <json-string> <member|index> [<member|index> ...])
Remove an element from ``<json-string>`` at the location
given by the list of ``<member|index>`` arguments. The JSON string
without the removed element will be stored in ``<out-var>``.
.. _SET:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-variable>]
SET <json-string> <member|index> [<member|index> ...] <value>)
Set an element in ``<json-string>`` at the location
given by the list of ``<member|index>`` arguments to ``<value>``.
The contents of ``<value>`` should be valid JSON.
.. _EQUAL:
.. code-block:: cmake
string(JSON <out-var> [ERROR_VARIABLE <error-var>]
EQUAL <json-string1> <json-string2>)
Compare the two JSON objects given by ``<json-string1>`` and ``<json-string2>``
for equality. The contents of ``<json-string1>`` and ``<json-string2>``
should be valid JSON. The ``<out-var>`` will be set to a true value if the
JSON objects are considered equal, or a false value otherwise.