github.com/rstandt/terraform@v0.12.32-0.20230710220336-b1063613405c/website/docs/configuration/functions/regex.html.md (about) 1 --- 2 layout: "functions" 3 page_title: "regex - Functions - Configuration Language" 4 sidebar_current: "docs-funcs-string-regex" 5 description: |- 6 The regex function applies a regular expression to a string and returns the 7 matching substrings. 8 --- 9 10 # `regex` Function 11 12 -> **Note:** This page is about Terraform 0.12 and later. For Terraform 0.11 and 13 earlier, see 14 [0.11 Configuration Language: Interpolation Syntax](../../configuration-0-11/interpolation.html). 15 16 `regex` applies a 17 [regular expression](https://en.wikipedia.org/wiki/Regular_expression) 18 to a string and returns the matching substrings. 19 20 ```hcl 21 regex(pattern, string) 22 ``` 23 24 The return type of `regex` depends on the capture groups, if any, in the 25 pattern: 26 27 - If the pattern has no capture groups at all, the result is a single string 28 covering the substring matched by the pattern as a whole. 29 - If the pattern has one or more _unnamed_ capture groups, the result is a 30 list of the captured substrings in the same order as the definition of 31 the capture groups. 32 - If the pattern has one or more _named_ capture groups, the result is a 33 map of the captured substrings, using the capture group names as map keys. 34 35 It's not valid to mix both named and unnamed capture groups in the same pattern. 36 37 If the given pattern does not match at all, the `regex` raises an error. To 38 _test_ whether a given pattern matches a string, use 39 [`regexall`](./regexall.html) and test that the result has length greater than 40 zero. 41 42 The pattern is a string containing a mixture of literal characters and special 43 matching operators as described in the following table. Note that when giving a 44 regular expression pattern as a literal quoted string in the Terraform 45 language, the quoted string itself already uses backslash `\` as an escape 46 character for the string, so any backslashes intended to be recognized as part 47 of the pattern must be escaped as `\\`. 48 49 | Sequence | Matches | 50 | -------------- | -------------------------------------------------------------------------------- | 51 | `.` | Any character except newline | 52 | `[xyz]` | Any character listed between the brackets (`x`, `y`, and `z` in this example) | 53 | `[a-z]` | Any character between `a` and `z`, inclusive | 54 | `[^xyz]` | The opposite of `[xyz]` | 55 | `\d` | ASCII digits (0 through 9, inclusive) | 56 | `\D` | Anything except ASCII digits | 57 | `\s` | ASCII spaces (space, tab, newline, carriage return, form feed) | 58 | `\S` | Anything except ASCII spaces | 59 | `\w` | The same as `[0-9A-Za-z_]` | 60 | `\W` | Anything except the characters matched by `\w` | 61 | `[[:alnum:]]` | The same as `[0-9A-Za-z]` | 62 | `[[:alpha:]]` | The same as `[A-Za-z]` | 63 | `[[:ascii:]]` | Any ASCII character | 64 | `[[:blank:]]` | ASCII tab or space | 65 | `[[:cntrl:]]` | ASCII/Unicode control characters | 66 | `[[:digit:]]` | The same as `[0-9]` | 67 | `[[:graph:]]` | All "graphical" (printable) ASCII characters | 68 | `[[:lower:]]` | The same as `[a-z]` | 69 | `[[:print:]]` | The same as `[[:graph:]]` | 70 | `[[:punct:]]` | The same as `` [!-/:-@[-`{-~] `` | 71 | `[[:space:]]` | The same as `[\t\n\v\f\r ]` | 72 | `[[:upper:]]` | The same as `[A-Z]` | 73 | `[[:word:]]` | The same as `\w` | 74 | `[[:xdigit:]]` | The same as `[0-9A-Fa-f]` | 75 | `\pN` | Unicode character class by using single-letter class names ("N" in this example) | 76 | `\p{Greek}` | Unicode character class by unicode name ("Greek" in this example) | 77 | `\PN` | The opposite of `\pN` | 78 | `\P{Greek}` | The opposite of `\p{Greek}` | 79 | `xy` | `x` followed immediately by `y` | 80 | `x|y` | either `x` or `y`, preferring `x` | 81 | `x*` | zero or more `x`, preferring more | 82 | `x*?` | zero or more `x`, preferring fewer | 83 | `x+` | one or more `x`, preferring more | 84 | `x+?` | one or more `x`, preferring fewer | 85 | `x?` | zero or one `x`, preferring one | 86 | `x??` | zero or one `x`, preferring zero | 87 | `x{n,m}` | between `n` and `m` repetitions of `x`, preferring more | 88 | `x{n,m}?` | between `n` and `m` repetitions of `x`, preferring fewer | 89 | `x{n,}` | at least `n` repetitions of `x`, preferring more | 90 | `x{n,}?` | at least `n` repetitions of `x`, preferring fewer | 91 | `x{n}` | exactly `n` repetitions of `x` | 92 | `(x)` | unnamed capture group for sub-pattern `x` | 93 | `(?P<name>x)` | named capture group, named `name`, for sub-pattern `x` | 94 | `(?:x)` | non-capturing sub-pattern `x` | 95 | `\*` | Literal `*` for any punctuation character `*` | 96 | `\Q...\E` | Literal `...` for any text `...` as long as it does not include literally `\E` | 97 98 In addition to the above matching operators that consume the characters they 99 match, there are some additional operators that _only_ match, but consume 100 no characters. These are "zero-width" matching operators: 101 102 | Sequence | Matches | 103 | -------- | ------------------------------------------------------------------------------------------------ | 104 | `^` | At the beginning of the given string | 105 | `$` | At the end of the given string | 106 | `\A` | At the beginning of the given string | 107 | `\z` | At the end of the given string | 108 | `\b` | At an ASCII word boundary (transition between `\w` and either `\W`, `\A` or `\z`, or vice-versa) | 109 | `\B` | Not at an ASCII word boundary | 110 111 Terraform uses the 112 [RE2](https://github.com/google/re2/wiki/Syntax) regular expression language. 113 This engine does not support all of the features found in some other regular 114 expression engines; in particular, it does not support backreferences. 115 116 ## Matching Flags 117 118 Some of the matching behaviors described above can be modified by setting 119 matching flags, activated using either the `(?flags)` operator (to activate 120 within the current sub-pattern) or the `(?flags:x)` operator (to match `x` with 121 the modified flags). Each flag is a single letter, and multiple flags can be 122 set at once by listing multiple letters in the `flags` position. 123 The available flags are listed in the table below: 124 125 | Flag | Meaning | 126 | ---- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- | 127 | `i` | Case insensitive: a literal letter in the pattern matches both lowercase and uppercase versions of that letter | 128 | `m` | The `^` and `$` operators also match the beginning and end of lines within the string, marked by newline characters; behavior of `\A` and `\z` is unchanged | 129 | `s` | The `.` operator also matches newline | 130 | `U` | The meaning of presence or absense `?` after a repetition operator is inverted. For example, `x*` is interpreted like `x*?` and vice-versa. | 131 132 ## Examples 133 134 ``` 135 > regex("[a-z]+", "53453453.345345aaabbbccc23454") 136 aaabbbccc 137 138 > regex("(\\d\\d\\d\\d)-(\\d\\d)-(\\d\\d)", "2019-02-01") 139 [ 140 "2019", 141 "02", 142 "01", 143 ] 144 145 > regex("^(?:(?P<scheme>[^:/?#]+):)?(?://(?P<authority>[^/?#]*))?", "https://terraform.io/docs/") 146 { 147 "authority" = "terraform.io" 148 "scheme" = "https" 149 } 150 151 > regex("[a-z]+", "53453453.34534523454") 152 153 Error: Error in function call 154 155 Call to function "regex" failed: pattern did not match any part of the given 156 string. 157 ``` 158 159 ## Related Functions 160 161 - [`regexall`](./regexall.html) searches for potentially multiple matches of a given pattern in a string. 162 - [`replace`](./replace.html) replaces a substring of a string with another string, optionally matching using the same regular expression syntax as `regex`. 163 164 If Terraform already has a more specialized function to parse the syntax you 165 are trying to match, prefer to use that function instead. Regular expressions 166 can be hard to read and can obscure your intent, making a configuration harder 167 to read and understand.