EXPR(1) EXPR(1)
NAME
expr - integer and string-match expression evaluator for
shell scripts
SYNOPSIS
expr arg ...
DESCRIPTION
The arguments are taken as an expression. After evaluation,
the result is written on the standard output. Each token of
the expression is a separate argument.
The operators and keywords are listed below in order of
increasing precedence, with equal precedence operators
grouped.
expr1 | expr2
Value is the value of expr1 if that is neither
empty nor 0, otherwise the value of expr2.
expr1 & expr2
Value is the value of expr1 if neither expr1 nor
expr2 is empty or 0, otherwise 0.
expr1 relop expr2
Relop is one of `< <= = != >= > .' Value is 1 if
the indicated comparison is true, 0 if false. The
comparison is numeric if both expr are integers,
otherwise lexicographic.
expr1 + expr2
expr1 - expr2
Value is the sum or difference of the (integer)
values of expr1 and expr2.
expr1 * expr2
expr1 / expr2
expr1 % expr2
Value is the product, quotient, or remainder of the
(integer) values of expr1 and expr2.
expr : regexp
Match the string value of expr with the regular
expression regexp; regular expression syntax is the
same as in ed(1), but matches are anchored at the
left. On success a subexpression \(...\), if pre-
sent in regexp, picks out a return value from the
matched string. Otherwise, the matching operator
yields the number of characters matched (0 on fail-
ure).
EXPR(1) EXPR(1)
( expr ) Parentheses for grouping.
arg Value is the string arg.
EXAMPLES
a=`expr $a + 1`
Add 1 to shell variable a.
expr $a : '.*/\(.*\)' '|' $a
Same as `basename $a'.
SEE ALSO
sh(1), test(1)
DIAGNOSTICS
Expr returns exit code 0 if the expression is neither null
nor 0, 1 if the expression is null or 0, 2 for invalid
expressions.