expr(1) | expr(1) |
International Code Set Support
Single- and
RETURN VALUE
As a side effect of expression evaluation, expr returns the following exit values:
0Expression is neither null nor zero.
1Expression is null or zero.
2Invalid expression.
>2 An error occurred while evaluating the expression.
DIAGNOSTICS |
| Operator or operand errors |
syntax error | ||
argument | Arithmetic attempted on a string | |
EXAMPLES |
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Add 1 to the shell variable a: |
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a=`expr | $a + 1` |
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For $a equal to either /usr/abc/file or just file, return the last segment of a path name (i.e., file). Beware of / alone as an argument because expr interprets it as the division operator (see WARNINGS below):
expr $a : '.*/\(.*\)' \ $a
A better representation of the previous example. The addition of the // characters eliminates any ambiguity about the division operator and simpli®es the whole expression:
expr //$a : '.*/\(.*\)'
Return the number of characters in $VAR:
expr $VAR : '.*'
WARNINGS
After argument processing by the shell, expr cannot tell the difference between an operator and an operand except by the value. If $a is an =, the command:
expr $a = '='
resembles:
expr = = =
as the arguments are passed to expr (and they will all be taken as the = operator). The following works:
expr X$a = X=
AUTHOR
expr was developed by OSF and HP.
SEE ALSO
sh(1), test(1), environ(5), lang(5), regexp(5).
STANDARDS CONFORMANCE
expr: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2
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