term% cat index.txt EXPR(1) General Commands Manual EXPR(1)
NAME
expr - evaluate arguments as an expression
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. The list is in order of
increasing precedence, with equal precedence operators grouped.
expr | expr
yields the first expr if it is neither null nor `0', otherwise
yields the second expr.
expr & expr
yields the first expr if neither expr is null or `0', otherwise
yields `0'.
expr relop expr
where relop is one of < <= = != >= >, yields `1' if the indi‐
cated comparison is true, `0' if false. The comparison is nu‐
meric if both expr are integers, otherwise lexicographic.
expr + expr
expr - expr
addition or subtraction of the arguments.
expr * expr
expr / expr
expr % expr
multiplication, division, or remainder of the arguments.
expr : expr
The matching operator compares the string first argument with
the regular expression second argument; regular expression syn‐
tax is the same as that of ed(1). The \(...\) pattern symbols
can be used to select a portion of the first argument. Other‐
wise, the matching operator yields the number of characters
matched (`0' on failure).
( expr )
parentheses for grouping.
Examples:
To add 1 to the Shell variable a:
a=`expr $a + 1`
To find the filename part (least significant part) of the pathname
stored in variable a, which may or may not contain `/':
expr $a : '.*/\(.*\)' '|' $a
Note the quoted Shell metacharacters.
SEE ALSO
ed(1), sh(1), test(1)
DIAGNOSTICS
Expr returns the following exit codes:
0 if the expression is neither null nor `0',
1 if the expression is null or `0',
2 for invalid expressions.
EXPR(1)