projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 3cc4e5af DR |
1 | .pa 1 |
| 2 | .he 'IF (I)'3/15/72'IF (I)' | |
| 3 | .ti 0 | |
| 4 | NAME if -- conditional command | |
| 5 | .sp | |
| 6 | .ti 0 | |
| 7 | SYNOPSIS if\b\b__ expr command [ arg\e91\e8 ... ] | |
| 8 | .sp | |
| 9 | .ti 0 | |
| 10 | DESCRIPTION if\b\b__ | |
| 11 | evaluates the expression expr\b\b\b\b____, and if its value is true\b\b\b\b____, | |
| 12 | executes the given command\b\b\b\b\b\b\b_______ with the given arguments. | |
| 13 | ||
| 14 | The following primitives are used to construct | |
| 15 | the expr\b\b\b\b____: | |
| 16 | ||
| 17 | .in +9 | |
| 18 | .ti -4 | |
| 19 | -r\b\b__ file | |
| 20 | .br | |
| 21 | true if the file exists and is readable. | |
| 22 | ||
| 23 | .ti -4 | |
| 24 | -w\b\b__ file | |
| 25 | .br | |
| 26 | true if the file exists and is writable | |
| 27 | ||
| 28 | .ti -4 | |
| 29 | s1 =\b_ s2 | |
| 30 | .br | |
| 31 | true if the strings s1\b\b__ and s2\b\b__ are equal. | |
| 32 | ||
| 33 | .ti -4 | |
| 34 | s1 !=\b\b__ s2 | |
| 35 | .br | |
| 36 | true if the strings s1\b\b__ and s2\b\b__ are not equal. | |
| 37 | ||
| 38 | .in -9 | |
| 39 | These primaries may be combined with the | |
| 40 | following operators: | |
| 41 | ||
| 42 | .in +5 | |
| 43 | !\b_ | |
| 44 | .ti +4 | |
| 45 | unary negation operator | |
| 46 | ||
| 47 | -a\b\b__ | |
| 48 | .ti +4 | |
| 49 | binary and\b\b\b___ operator | |
| 50 | ||
| 51 | -o\b\b__ | |
| 52 | .ti +4 | |
| 53 | binary or\b\b__ operator | |
| 54 | ||
| 55 | (\b_ expr )\b_ | |
| 56 | .ti +4 | |
| 57 | parentheses for grouping. | |
| 58 | ||
| 59 | .in -5 | |
| 60 | -a\b\b__ has higher precedence than -o\b\b__. | |
| 61 | Notice that all the operators and flags are separate | |
| 62 | arguments to if\b\b__ and hence must be surrounded by spaces. | |
| 63 | .sp | |
| 64 | .ti 0 | |
| 65 | FILES -- | |
| 66 | .sp | |
| 67 | .ti 0 | |
| 68 | SEE ALSO sh(I) | |
| 69 | .sp | |
| 70 | .ti 0 | |
| 71 | DIAGNOSTICS "if error", | |
| 72 | if the expression has the wrong syntax; | |
| 73 | "command not found." | |
| 74 | .sp | |
| 75 | .ti 0 | |
| 76 | BUGS -- |