string¶
String operations.
Synopsis¶
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> <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 | LENGTH | 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¶
- string(FIND <string> <substring> <output_variable> [REVERSE])¶
Return the position where the given
<substring>was found in the supplied<string>. If theREVERSEflag 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.
- 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¶
- 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.
- 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.
- 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¶
The following characters have special meaning in regular expressions:
^Matches at beginning of input
$Matches at end of input
.Matches any single character
\<char>Matches the single character specified by
<char>. Use this to match special regex characters, e.g.\.for a literal.or\\for a literal backslash\. Escaping a non-special character is unnecessary but allowed, e.g.\amatchesa.[ ]Matches any character(s) inside the brackets. To match a literal
], make it the first character, e.g.,[]ab].[^ ]Matches any character(s) not inside the brackets. To not match a literal
], make it the first character, e.g.,[^]ab].-Inside brackets, specifies an inclusive range between characters on either side, e.g.,
[a-f]is[abcdef]. To match a literal-using brackets, make it the first or the last character, e.g.,[+*/-]matches basic mathematical operators.*Matches preceding pattern zero or more times
+Matches preceding pattern one or more times
?Matches preceding pattern zero or once only
|Matches a pattern on either side of the
|()Saves a matched subexpression, which can be referenced in the
REGEX REPLACEoperation.New in version 3.9: All regular expression-related commands, including e.g.
if(MATCHES), save subgroup matches in the variablesCMAKE_MATCH_<n>for<n>0..9.
*, + and ? have higher precedence than concatenation. |
has lower precedence than concatenation. This means that the regular
expression ^ab+d$ matches abbd but not ababd, and the regular
expression ^(ab|cd)$ matches ab but not abd.
CMake language 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 Bracket Argument without having to escape the backslashes, e.g.[[\(\a\+\b\)]].
Manipulation¶
- string(APPEND <string_variable> [<input>...])¶
New in version 3.4.
Append all the
<input>arguments to the string.
- string(PREPEND <string_variable> [<input>...])¶
New in version 3.10.
Prepend all the
<input>arguments to the string.
- string(CONCAT <output_variable> [<input>...])¶
Concatenate all the
<input>arguments together and store the result in the named<output_variable>.
- string(JOIN <glue> <output_variable> [<input>...])¶
New in version 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
JOINoperator from thelist()command. This allows for the elements to have special characters like;in them.
- string(TOLOWER <string> <output_variable>)¶
Convert
<string>to lower characters.
- string(TOUPPER <string> <output_variable>)¶
Convert
<string>to upper characters.
- 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.
- string(SUBSTRING <string> <begin> <length> <output_variable>)¶
Store in an
<output_variable>a substring of a given<string>. If<length>is-1the remainder of the string starting at<begin>will be returned.Changed in version 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.
- string(STRIP <string> <output_variable>)¶
Store in an
<output_variable>a substring of a given<string>with leading and trailing spaces removed.
- string(GENEX_STRIP <string> <output_variable>)¶
New in version 3.1.
Strip any
generator expressionsfrom the input<string>and store the result in the<output_variable>.
- string(REPEAT <string> <count> <output_variable>)¶
New in version 3.15.
Produce the output string as the input
<string>repeated<count>times.
Comparison¶
- 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>.New in version 3.7: Added the
LESS_EQUALandGREATER_EQUALoptions.
Hashing¶
- string(<HASH> <output_variable> <input>)¶
Compute a cryptographic hash of the
<input>string. The supported<HASH>algorithm names are:MD5Message-Digest Algorithm 5, RFC 1321.
SHA1US Secure Hash Algorithm 1, RFC 3174.
SHA224US Secure Hash Algorithms, RFC 4634.
SHA256US Secure Hash Algorithms, RFC 4634.
SHA384US Secure Hash Algorithms, RFC 4634.
SHA512US Secure Hash Algorithms, RFC 4634.
SHA3_224Keccak SHA-3.
SHA3_256Keccak SHA-3.
SHA3_384Keccak SHA-3.
SHA3_512Keccak SHA-3.
New in version 3.8: Added the
SHA3_*hash algorithms.
Generation¶
- string(ASCII <number> [<number> ...] <output_variable>)¶
Convert all numbers into corresponding ASCII characters.
- string(HEX <string> <output_variable>)¶
New in version 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 (athroughf) are in lowercase.
- string(CONFIGURE <string> <output_variable> [@ONLY] [ESCAPE_QUOTES])¶
Transform a
<string>likeconfigure_file()transforms a file.
- 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.
- 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 integerRANDOM_SEEDis given, its value will be used to seed the random number generator.
- 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
UTCflag 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:%%New in version 3.8.
A literal percent sign (%).
%dThe day of the current month (01-31).
%HThe hour on a 24-hour clock (00-23).
%IThe hour on a 12-hour clock (01-12).
%jThe day of the current year (001-366).
%mThe month of the current year (01-12).
%bNew in version 3.7.
Abbreviated month name (e.g. Oct).
%BNew in version 3.10.
Full month name (e.g. October).
%MThe minute of the current hour (00-59).
%sNew in version 3.6.
Seconds since midnight (UTC) 1-Jan-1970 (UNIX time).
%SThe second of the current minute. 60 represents a leap second. (00-60)
%fNew in version 3.23.
The microsecond of the current second (000000-999999).
%UThe week number of the current year (00-53).
%VNew in version 3.22.
The ISO 8601 week number of the current year (01-53).
%wThe day of the current week. 0 is Sunday. (0-6)
%aNew in version 3.7.
Abbreviated weekday name (e.g. Fri).
%ANew in version 3.10.
Full weekday name (e.g. Friday).
%yThe last two digits of the current year (00-99).
%YThe current year.
%zNew in version 3.26.
The offset of the time zone from UTC, in hours and minutes, with format
+hhmmor-hhmm.%ZNew in version 3.26.
The time zone name.
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.
New in version 3.8: If the
SOURCE_DATE_EPOCHenvironment variable is set, its value will be used instead of the current time. See https://reproducible-builds.org/specs/source-date-epoch/ for details.
- string(UUID <output_variable> NAMESPACE <namespace> NAME <name> TYPE <MD5|SHA1> [UPPER])¶
New in version 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 eitherMD5(Version 3 UUID) orSHA1(Version 5 UUID). A UUID has the formatxxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxxwhere eachxrepresents a lower case hexadecimal character. Where required, an uppercase representation can be requested with the optionalUPPERflag.
JSON¶
New in version 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.
- 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 asONorOFF. Null elements will be returned as an empty string. Number and string types will be returned as strings.
- 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 ofNULL,NUMBER,STRING,BOOLEAN,ARRAY, orOBJECT.
- 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.
- string(JSON <out-var> [ERROR_VARIABLE <error-variable>] LENGTH <json-string> [<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.
- 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>.
- 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. If<json-string>is an array,<value>can be appended to the end of the array by using a number greater or equal to the array length as the<member|index>argument.
- 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.