Manual page for EXPR(1)
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 indicated comparison is true, `0' if false.
The comparison is numeric 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
-
- match expr expr
-
compares the first argument (a string)
with the second argument (a regular expression);
regular expression syntax is the same as that of
ed.1
The
\(...\)
pattern symbols can be used to select a portion of the
first argument.
Otherwise,
this operator yields the number of characters matched
(`0' on failure).
- index expr expr
-
finds the second argument (a string) in the first.
Returns the location of the first matched character
(where the first character is at location `1')
or `0' if the second argument is not a substring of the first.
- substr expr expr expr
-
returns the substring of the first argument (a string)
that starts at the position specified by the second argument
(where `1' refers to the first character)
and has length equal to the third argument (a numeral).
- length expr
-
returns the length of the argument (a string).
- ( 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
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.
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97
