'\"! tbl|mmdoc
'\"macro stdmacro
.if n .pH g1.expr @(#)expr	41.8 of 5/26/91
.\" Copyright 1991 UNIX System Laboratories, Inc.
.\" Copyright 1989, 1990 AT&T
.nr X
.if \nX=0 .ds x} expr 1 "Essential Utilities" "\&"
.if \nX=1 .ds x} expr 1 "Essential Utilities"
.if \nX=2 .ds x} expr 1 "" "\&"
.if \nX=3 .ds x} expr "" "" "\&"
.TH \*(x}
.if t .ds ' \h@.05m@\s+4\v@.333m@\'\v@-.333m@\s-4\h@.05m@
.if n .ds ' '
.if t .ds ` \h@.05m@\s+4\v@.333m@\`\v@-.333m@\s-4\h@.05m@
.if n .ds ` `
.SH NAME
\f4expr\f1 \- evaluate arguments as an expression
.SH SYNOPSIS
\f4expr\f1
.I arguments
.SH DESCRIPTION
The
.I arguments
are taken as an expression.
After evaluation, the result is written on the standard output.
Terms of the expression must be separated by blanks.
Characters special to the shell
must be escaped.
Note that \f40\fP is returned to indicate a zero value,
rather than the null string.
Strings containing blanks or other special characters should be quoted.
Integer-valued arguments may be preceded by a unary minus sign.
Internally, integers are treated as 32-bit, 2s complement numbers.
The length of the expression is limited to 512 bytes.
\f4expr\fP processes supplementary code set characters
according to the locale specified in the \f4LC_CTYPE\fP
environment variable [see \f4LANG\fP on \f4environ\fP(5)].
In regular expressions, pattern searches are performed
on characters, not bytes, as described in \f4regcomp\f1(5).
.PP
The operators and keywords are listed below.  Characters that need to be 
escaped in the shell [see \f4sh\fP(1)] are preceded by \f4\\\fP.  The list 
is in order of increasing precedence, with equal precedence operators 
grouped within \f4{\|}\fP symbols.
.TP .5i
\f2expr1 \f4\e|\f2 expr2\f1
returns the evaluation of \f2expr1\fP if it is neither null nor \f40\fP, 
otherwise returns the evaluation of \f2expr2\fP.
.TP .5i
\f2expr1 \f4\e&\f2 expr2\f1
returns the evaluation of \f2expr1\fP
if neither expression evaluates
to null or \f40\fP, otherwise returns \f40\fP.
.sp
Returns the result of a decimal integer comparison if both arguments
are integers; otherwise, returns the result of a string comparison using
the locale-specific collation sequence. The result of each comparison
will be \f41\fP if the specified relationship is true, or \f40\fP if the
relationship is false.
.TP .5i
\f2expr1 \f1{ \f4=\f1, \f4\e>\f1, \f4\e>=\f1, \f4\e<\f1, \f4\e<=\f1, \f4!=\f1 } \f2expr2\fP
returns the result of an integer comparison if both arguments are integers,
otherwise returns the result of a lexical comparison.
.TP .5i
\f2expr1 \f1{ \f4+\f1, \f4\- \f1} \f2expr2\fP
addition or subtraction of decimal integer-valued arguments.
.TP .5i
\f2expr1 \f1{ \f4\e\(**\f1, \f4/\f1, \f4% \f1} \f2expr2\fP
multiplication, division, or remainder of the decimal integer-valued 
arguments.
.TP .5i
\f2expr1\f4 : \f2expr2\f1
The matching operator \f4:\fP compares \f2expr1\fP
with \f2expr2\fP, which must be a regular expression.
Regular expression syntax is defined is defined in the
\f4regcomp(5)\fP man page under the section titled: 
\f2Basic Regular Expression\fP, Normally,
the matching operator returns the number of bytes matched
(\f40\fP on failure).  Alternatively, if the pattern contains at least 
one regular expression subexpression [\\( . . .\\)], the string 
corresponding to \\1 will be returned.
.PP
The use of string arguments \f4length\fP, \f4substr\fP, \f4index\fP or
\f4match\fP produces unspecified results.
.SH EXAMPLES
Add 1 to the shell variable
\f4a\fP:
.PP
.RS
.ft 4
a=\*`expr\| $a\| +\| 1\*`
.ft 1
.RE
.ne 5
.PP
The following example emulates
\f4basename\fP(1)\-it returns the last segment of the path name \f4$a\fP.
For \f4$a\fP equal to either \f4/usr/abc/file\fP or just \f4file\fP, the 
example returns \f4file\fP.  (Watch out for \f4/\fP alone as an argument:
\f4expr\fP takes it as the division operator; see the NOTES below.)
.PP
.RS
.ft 4
expr $a : \*'.\(**/\e(.\(**\e)\*' \e| $a
.ft 1
.RE
.PP
Here is a better version of the previous example.
The addition of the
\f4//\f1
characters eliminates any ambiguity about the division operator and 
simplifies the whole expression.
.PP
.RS
.ft 4
expr //$a : \*'.\(**/\e(.\(**\e)\*'
.ft 1
.RE
.PP
Return the number of characters in
\f4$VAR\f1:
.PP
.RS
.ft 4
expr $VAR : \*'.\(**\*'
.ft 1
.RE
.SH FILES
.TP
\f4/usr/lib/locale/\f2locale\f4/LC_MESSAGES/uxcore.abi\f1
language-specific message file [See \f4LANG\fP on \f4environ\f1 (5).]
.SH "SEE ALSO"
\f4regcomp\fP(5), \f4sh\fP(1)
.SH STDOUT
\f2expr\fP will evaluate the expression and write the result to standard 
output. The character \f40\fP will be written to indicate a zero value and 
nothing will be written to indicate a null string.
.SH STDERR
Used only for diagnostic messages.
.SH DIAGNOSTICS
As a side effect of expression evaluation,
\f4expr\fP
returns the following exit values:
.TS
n l.
0	if the expression is neither null nor \f40\fP
1	if the expression is null or \f40\fP
2	for invalid expressions.
>2	An error occurred.
.TE
.PP
.PD 0
.TP 1.75i
\f4syntax error\fP
for operator/operand errors
.TP
\f4non-numeric argument\fP
if arithmetic is attempted on such a string
.PD
.SH NOTES
After argument processing by the shell,
\f4expr\fP
cannot tell the difference between an operator and an operand
except by the value.
If
\f4$a\f1
is an
\f4=\f1,
the command:
.PP
.RS
.ft 4
expr $a = \*'=\*'
.ft 1
.RE
.PP
looks like:
.PP
.RS
.ft 4
expr = = =
.ft 1
.RE
.PP
as the arguments are passed to
\f4expr\fP
(and they are all taken as the
\f4=\f1
operator).
The following works:
.PP
.RS
.ft 4
expr X$a = X=
.ft 1
.RE
.\"	@(#)expr.1	6.2 of 9/2/83
.Ee