| Roland Gaudig | d5ae0ec | 2021-07-23 12:29:22 +0000 | [diff] [blame] | 1 | .. SPDX-License-Identifier: GPL-2.0+ |
| 2 | |
| 3 | setexpr command |
| 4 | =============== |
| 5 | |
| 6 | Synopsis |
| 7 | -------- |
| 8 | |
| 9 | :: |
| 10 | |
| 11 | setexpr[.b, .w, .l .s] <name> [*]<value> <op> [*]<value2> |
| 12 | setexpr[.b, .w, .l] <name> [*]<value> |
| 13 | setexpr <name> fmt <format> [value]... |
| 14 | setexpr <name> gsub r s [t] |
| 15 | setexpr <name> sub r s [t] |
| 16 | |
| 17 | Description |
| 18 | ----------- |
| 19 | |
| 20 | The setexpr command is used to set an environment variable to the result |
| 21 | of an evaluation. |
| 22 | |
| 23 | setexpr[.b, .w, .l .s] <name> [*]<value> <op> [*]<value2> |
| 24 | Set environment variable <name> to the result of the evaluated |
| 25 | expression specified by <op>. |
| 26 | |
| 27 | setexpr[.b, .w, .l] name [*]value |
| 28 | Load <value> into environment variable <name> |
| 29 | |
| 30 | setexpr name fmt <format> value |
| 31 | Set environment variable <name> to the result of the C like |
| 32 | format string <format> evaluation of <value>. |
| 33 | |
| 34 | setexpr name gsub <r> <s> [<t>] |
| 35 | For each substring matching the regular expression <r> in the |
| 36 | string <t>, substitute the string <s>. |
| 37 | The result is assigned to <name>. |
| 38 | If <t> is not supplied, use the old value of <name>. |
| 39 | |
| 40 | setexpr name sub <r> <s> [<t>] |
| 41 | Just like gsub(), but replace only the first matching substring |
| 42 | |
| 43 | The setexpr command takes the following arguments: |
| 44 | |
| 45 | format |
| 46 | This parameter contains a C or Bash like format string. |
| 47 | The number of arguments is limited to 4. |
| 48 | The following format types are supported: |
| 49 | |
| 50 | c |
| 51 | single character |
| 52 | d, i |
| 53 | decimal value |
| 54 | o |
| 55 | octal value |
| 56 | s |
| 57 | string |
| 58 | u |
| 59 | unsigned decimal value |
| 60 | x, X |
| 61 | hexadecimal value |
| 62 | '%' |
| 63 | no conversion, instead a % character will be written |
| 64 | |
| 65 | Backslash escapes: |
| 66 | |
| 67 | \" = double quote |
| 68 | \\ = backslash |
| 69 | \a = alert (bell) |
| 70 | \b = backspace |
| 71 | \c = produce no further output |
| 72 | \f = form feed |
| 73 | \n = new line |
| 74 | \r = carriage return |
| 75 | \t = horizontal tab |
| 76 | \v = vertical tab |
| 77 | \NNN = octal number (NNN is 0 to 3 digits) |
| 78 | |
| 79 | name |
| 80 | The name of the environment variable to be set |
| 81 | |
| 82 | op |
| 83 | '|' |
| 84 | name = value | value2 |
| 85 | '&' |
| 86 | name = value & value2 |
| 87 | '+' |
| 88 | name = value + value2 |
| 89 | (This is the only operator supported for strings. |
| 90 | It acts as concatenation operator on strings) |
| 91 | '^' |
| 92 | name = value ^ value2 |
| 93 | '-' |
| 94 | name = value - value2 |
| 95 | '*' |
| 96 | name = value * value2 |
| 97 | '/' |
| 98 | name = value / value2 |
| 99 | '%' |
| 100 | name = value % value2 |
| 101 | |
| 102 | r |
| 103 | Regular expression |
| 104 | |
| 105 | s |
| 106 | Substitution string |
| 107 | |
| 108 | t |
| 109 | string |
| 110 | |
| 111 | value |
| 112 | Can either be an integer value, a string. |
| 113 | If the pointer prefix '*' is given value is treated as memory address. |
| 114 | |
| 115 | value2 |
| 116 | See value |
| 117 | |
| 118 | Example |
| 119 | ------- |
| 120 | |
| 121 | :: |
| 122 | |
| 123 | => setexpr foo fmt %d 0x100 |
| 124 | => echo $foo |
| 125 | 256 |
| 126 | => |
| 127 | |
| 128 | => setexpr foo fmt 0x%08x 63 |
| 129 | => echo $foo |
| 130 | 0x00000063 |
| 131 | => |
| 132 | |
| 133 | => setexpr foo fmt %%%o 8 |
| 134 | => echo $foo |
| 135 | %10 |
| 136 | => |
| 137 | |
| 138 | Configuration |
| 139 | ------------- |
| 140 | |
| 141 | The setexpr gsub and sub operations are only available if CONFIG_REGEX=y. |
| 142 | |
| 143 | Return value |
| 144 | ------------ |
| 145 | |
| 146 | The return value $? is set to 0 (true) if the operation was successful. |
| 147 | |
| 148 | If an error occurs, the return value $? is set to 1 (false). |