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.\" Sccsid @(#)expr.1	1.16 (gritter) 2/3/05
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.TH EXPR 1 "2/3/05" "Heirloom Toolchest" "User Commands"
.SH NAME
expr \- evaluate arguments as an expression
.SH SYNOPSIS
.B expr
.I arguments
\&.\|.\|.
.SH 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.
.PP
The operators and keywords are listed below.
The list is in order of increasing precedence,
with equal precedence operators grouped.
.TP
.I expr | expr
yields the first
.I expr
if it is neither null nor `0', otherwise
yields the second
.I expr.
.TP
.I expr & expr
yields the first
.I expr
if neither
.I expr
is null or `0', otherwise yields `0'.
.TP
.I expr relop expr
where
.I relop is one of
< <= = != >= >,
yields `1' if the indicated comparison is true, `0' if false.
The comparison is numeric if both
.I expr
are integers, otherwise lexicographic.
.TP
.IR expr " + " expr
.br
.IR expr " - " expr
.br
addition or subtraction of the arguments.
.TP
.IR expr " * " expr
.br
.IR expr " / " expr
.br
.IR expr " % " expr
.br
multiplication, division, or remainder of the arguments.
.TP
.IR expr " : " expr
The matching operator compares the string first argument
with the regular expression second argument.
Regular expression syntax is the same as that of
.IR ed (1);
.B /usr/5bin/expr
uses simple regular expressions,
.BR /usr/5bin/posix/expr ,
.BR /usr/5bin/posix2001/expr ,
and
.B /usr/5bin/s42/expr
use basic regular expressions.
The
\fB\\(\|.\|.\|.\|\\)\fP
pattern symbols can be used to select a portion of the
first argument.
Otherwise,
the matching operator yields the number of characters matched
(`0' on failure).
.TP
.RI match " expr expr"
Same as
.IR expr " : " expr .
.TP
.RI ( " expr " )
parentheses for grouping.
.TP
.I string
Yields itself
unless it is part of a larger expression.
With
.BR /usr/5bin/posix/expr
and
.BR /usr/5bin/posix2001/expr ,
all
.I strings
that form valid decimal numbers
are converted to the canonical form.
.PP
The following operators are supported only by
.B /usr/5bin/s42/expr
or if the
.B SYSV3
environment variable is set:
.TP
.RI length " string"
Returns the number of characters in
.IR string .
.TP
.RI substr " string index count"
Returns a string that consists of
.I count
characters
beginning at position
.I index
of
.I string
(starting at 1).
.TP
.RI index " string set"
Returns the index in
.I string
(starting at 1) of the first occurrence
of one of the characters in
.IR set ,
or 0 if no character is found.
.SH "ENVIRONMENT VARIABLES"
.TP
.BR LANG ", " LC_ALL
See locale(7).
.TP
.B LC_COLLATE
Sets the collation sequence for string comparison,
and for range expressions,
equivalence classes, and collation symbols
in basic regular expressions.
.TP
.B LC_CTYPE
Determines the mapping of bytes to characters in regular expressions,
for the match, length, substr, and index operators,
and the availability and composition of character classes
in basic regular expressions.
.TP
.B SYSV3
Enables some additional operators as described above.
.SH EXAMPLES
.PP
To add 1 to the Shell variable
.IR a :
.IP
a=\`expr $a + 1\`
.PP
To find the filename part (least significant part)
of the pathname stored in variable
.I a,
which may or may not contain `/':
.IP
expr "$a" : \'.*/\e(\^.*\e)\' \'\^|\' "$a"
.LP
Note the quoted Shell metacharacters.
.\" Historic example, not to be deleted and useful just because of its errors
Also note that this example generates wrong results
if the result of the substitution is `0'
or if `$a' equals one of the
.I expr
operators.
Be sure that your code avoids such problems
and use
.IR basename (1)
if to actually cut out filename parts.
.SH "SEE ALSO"
ed(1), sh(1), test(1)
.SH DIAGNOSTICS
.I Expr
returns the following exit codes:
.PP
	0	if the expression is neither null nor `0',
.br
	1	if the expression
is null or `0',
.br
	2	for invalid expressions.
.SH NOTES
Integers are treated as 64-bit, 2's complement numbers.