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.\" ========================================================================
.\"
.IX Title "EXPR 1"
.TH EXPR 1 "2001-06-06" "perl v5.20.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
expr \-\- evaluate expression
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
expr expression
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The expr utility evaluates expression and writes the result
on standard output.
.PP
All operators are separate arguments to the expr utility.  Characters
special to the command interpreter must be escaped.
.PP
Operators are listed below in order of increasing precedence.  Operators
with equal precedence are grouped within { } symbols.
.IP "expr1 | expr2" 4
.IX Item "expr1 | expr2"
Returns the evaluation of expr1 if it is neither an empty string
nor zero; otherwise, returns the evaluation of expr2.
.IP "expr1 & expr2" 4
.IX Item "expr1 & expr2"
Returns the evaluation of expr1 if neither expression evaluates
to an empty string or zero; otherwise, returns zero.
.IP "expr1 {=, >, >=, <, <=, !=} expr2" 4
.IX Item "expr1 {=, >, >=, <, <=, !=} expr2"
Returns the results of integer comparison if both arguments are
integers; otherwise, returns the results of string comparison us\-
ing the locale-specific collation sequence.  The result of each
comparison is 1 if the specified relation is true, or 0 if the
relation is false.
.IP "expr1 {+, \-} expr2" 4
.IX Item "expr1 {+, -} expr2"
Returns the results of addition or subtraction of integer-valued
arguments.
.IP "expr1 {*, /, %} expr2" 4
.IX Item "expr1 {*, /, %} expr2"
Returns the results of multiplication, integer division, or re\-
mainder of integer-valued arguments.
.IP "expr1 : expr2" 4
.IX Item "expr1 : expr2"
The ``:'' operator matches expr1 against expr2, which must be
a regular expression.  The regular expression is anchored to
the beginning of the string with an implicit ``^''.  The
regular expression language is \fIperlre\fR\|(1).
.Sp
If the match succeeds and the pattern contains at least one regu\-
lar expression subexpression ``(...)'', the string correspond\-
ing to ``$1'' is returned; otherwise the matching operator re\-
turns the number of characters matched.  If the match fails and
the pattern contains a regular expression subexpression the null
string is returned; otherwise 0.
.Sp
Parentheses are used for grouping in the usual manner.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
.IP "1." 4
The following example adds one to the variable a.
.Sp
.Vb 1
\& a=\`expr $a + 1\`
.Ve
.IP "2." 4
The following example returns the filename portion of a pathname
stored in variable a.  The // characters act to eliminate ambiguity
with the division operator.
.Sp
.Vb 1
\& expr //$a : \*(Aq.*/\e(.*\e)\*(Aq
.Ve
.IP "3." 4
The following example returns the number of characters in variable a.
.Sp
.Vb 1
\& expr $a : \*(Aq.*\*(Aq
.Ve
.SH "DIAGNOSTICS"
.IX Header "DIAGNOSTICS"
The expr utility exits with one of the following values:
.PP
.Vb 3
\& 0       the expression is neither an empty string nor 0.
\& 1       the expression is an empty string or 0.
\& 2       the expression is invalid.
.Ve
.SH "STANDARDS"
.IX Header "STANDARDS"
The expr utility conforms to \s-1IEEE\s0 Std1003.2 (``\s-1POSIX.2\s0'').
.SH "POD ERRORS"
.IX Header "POD ERRORS"
Hey! \fBThe above document had some coding errors, which are explained below:\fR
.IP "Around line 165:" 4
.IX Item "Around line 165:"
You forgot a '=back' before '=head1'