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'\" te .\" Copyright (c) 1989, AT&T. All rights reserved. .\" Copyright (c) 2003, 2022, Oracle and/or its affiliates. .\" Portions Copyright (c) 1992, The X/Open Company Ltd. All rights reserved. .\" Oracle gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at http://www.opengroup.org/bookstore/. .\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html. This notice shall appear on any product containing this material. .TH expr 1 "29 Nov 2022" "Oracle Solaris 11.4" "User Commands" .SH NAME expr \- evaluate arguments as an expression .SH SYNOPSIS .LP .nf \fB/usr/bin/expr\fR \fIargument\fR... .fi .LP .nf \fB/usr/xpg4/bin/expr\fR \fIargument\fR... .fi .LP .nf \fB/usr/xpg6/bin/expr\fR \fIargument\fR... .fi .SH DESCRIPTION .SS "/usr/bin/expr, /usr/xpg4/bin/expr" .sp .LP The \fBexpr\fR utility evaluates the expression and writes the result to standard output. The character \fB0\fR is written to indicate a zero value and nothing is written to indicate a null string. .SS "/usr/xpg6/bin/expr" .sp .LP The \fBexpr\fR utility evaluates the expression and writes the result to standard output followed by a NEWLINE. If there is no result from \fBexpr\fR processing, a NEWLINE is written to standard output. .SH OPERANDS .sp .LP The \fIargument\fR operand is evaluated as an expression. Terms of the expression must be separated by blanks. Characters special to the shell must be escaped (see \fBsh\fR(1)). Strings containing blanks or other special characters should be quoted. The length of the expression is limited to \fBLINE_MAX\fR (2048 characters). .sp .LP The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence operators grouped within \fB{\|}\fR symbols. All of the operators are left-associative. .sp .ne 2 .mk .na \fB\fIexpr\fR \fB|\fR \fIexpr\fR\fR .ad .br .sp .6 .RS 4n Returns the evaluation of the first \fIexpr\fR if it is neither \fINULL\fR nor \fB0\fR; otherwise, returns the evaluation of the second \fIexpr\fR if it is not \fINULL\fR; otherwise, \fB0\fR. .RE .sp .ne 2 .mk .na \fB\fIexpr\fR \fB&\fR \fIexpr\fR\fR .ad .br .sp .6 .RS 4n Returns the first \fIexpr\fR if neither \fIexpr\fR is \fINULL\fR or \fB0\fR, otherwise returns \fB0\fR. .RE .sp .ne 2 .mk .na \fB\fIexpr\fR { \fB=\fR, \fB>\fR, \fB>=\fR, \fB<\fR, \fB<=\fR, \fB!=\fR } \fIexpr\fR\fR .ad .br .sp .6 .RS 4n Returns the result of an integer comparison if both arguments are integers, otherwise returns the result of a string comparison using the locale-specific coalition sequence. The result of each comparison is \fB1\fR if the specified relationship is \fBTRUE\fR, \fB0\fR if the relationship is \fBFALSE\fR. .RE .sp .ne 2 .mk .na \fB\fIexpr\fR { \fB+\fR, \fB\(mi\fR } \fIexpr\fR\fR .ad .br .sp .6 .RS 4n Addition or subtraction of integer-valued arguments. .RE .sp .ne 2 .mk .na \fB\fIexpr\fR { \fB*\fR, \fB/\fR, \fB%\fR } \fIexpr\fR\fR .ad .br .sp .6 .RS 4n Multiplication, division, or remainder of the integer-valued arguments. .RE .sp .ne 2 .mk .na \fB\fIexpr\fR \fB:\fR \fIexpr\fR\fR .ad .br .sp .6 .RS 4n The matching operator \fB:\fR (colon) compares the first argument with the second argument, which must be an internationalized basic regular expression (BRE), except that all patterns are anchored to the beginning of the string. That is, only sequences starting at the first character of a string are matched by the regular expression. See \fBregex\fR(7) and NOTES. Normally, the \fB/usr/bin/expr\fR matching operator returns the number of bytes matched and the \fB/usr/xpg4/bin/expr\fR and \fB/usr/xpg6/bin/expr\fR matching operator returns the number of characters matched (\fB0\fR on failure). If the second argument contains at least one BRE sub-expression [\e(...\e)], the matching operator returns the string corresponding to \e1. .RE .sp .ne 2 .mk .na \fB\fIinteger\fR\fR .ad .br .sp .6 .RS 4n An argument consisting only of an (optional) unary minus followed by digits. .RE .sp .ne 2 .mk .na \fB\fIstring\fR\fR .ad .br .sp .6 .RS 4n A string argument that cannot be identified as an \fIinteger\fR argument or as one of the expression operator symbols. .RE .sp .LP The following four operators: \fBindex\fR, \fBlength\fR, \fBmatch\fR, and \fBsubstr\fR, are all at the same precedence: .sp .ne 2 .mk .na \fB\fBindex\fR \fIstring character-list\fR\fR .ad .br .sp .6 .RS 4n Report the first byte in \fIstring\fR (counting from one) where a byte from \fIcharacter-list\fR matches a byte from \fIstring\fR. If no bytes in \fIcharacter-list\fR appear in string, a \fB0\fR is returned. .RE .sp .ne 2 .mk .na \fB\fBlength\fR \fIstring\fR\fR .ad .br .sp .6 .RS 4n Return the length (that is, the number of bytes) of \fIstring\fR. The terminating nul character is not included in that count. .RE .sp .ne 2 .mk .na \fB\fBmatch\fR \fIstring regular-expression\fR\fR .ad .br .sp .6 .RS 4n Synonymous with the \fBexpr : expr\fR matching operator. .RE .sp .ne 2 .mk .na \fB\fBsubstr\fR \fIstring integer-1 integer-2\fR\fR .ad .br .sp .6 .RS 4n Extract the sequence of bytes from string (counting from one) starting at position \fIinteger-1\fR and of length \fIinteger-2\fR bytes. If \fIinteger-1\fR has a value greater than the number of bytes in string, \fBexpr\fR returns a null string. If you try to extract more bytes than there are in string, \fBexpr\fR returns all the remaining bytes from string. Results are unspecified if either \fIinteger-1\fR or \fIinteger-2\fR is a negative value. .RE .SH EXAMPLES .LP \fBExample 1\fR Adding an integer to a shell variable .sp .LP Add 1 to the shell variable \fBa\fR: .sp .in +2 .nf example$ \fBa=`expr\| $a\| +\| 1`\fR .fi .in -2 .sp .LP \fBExample 2\fR Returning a path name segment .sp .LP The following example emulates \fBbasename\fR(1), returning the last segment of the path name \fB$a\fR. For \fB$a\fR equal to either \fB/usr/abc/file\fR or just \fBfile\fR, the example returns \fBfile\fR. (Watch out for \fB/\fR alone as an argument: \fBexpr\fR takes it as the division operator. See NOTES below.) .sp .in +2 .nf example$ \fBexpr $a : '.*/\e(.*\e)' \e| $a\fR .fi .in -2 .sp .LP \fBExample 3\fR Using // characters to simplify the expression .sp .LP Here is a better version of the previous example. The addition of the \fB//\fR characters eliminates any ambiguity about the division operator and simplifies the whole expression. .sp .in +2 .nf example$ \fBexpr //$a : '.*/\e(.*\e)'\fR .fi .in -2 .sp .SS "/usr/bin/expr" .LP \fBExample 4\fR Returning the number of bytes in a variable .sp .in +2 .nf example$ \fBexpr "$VAR" : '.*'\fR .fi .in -2 .sp .SS "/usr/xpg4/bin/expr" .LP \fBExample 5\fR Returning the number of characters in a variable .sp .in +2 .nf example$ \fBexpr "$VAR" : '.*'\fR .fi .in -2 .sp .SH ENVIRONMENT VARIABLES .sp .LP See \fBenviron\fR(7) for descriptions of the following environment variables that affect the execution of \fBexpr\fR: \fBLANG\fR, \fBLC_ALL\fR, \fBLC_COLLATE\fR, \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR. .SH EXIT STATUS .sp .LP As a side effect of expression evaluation, \fBexpr\fR returns one of the following exit values if no error occurred: .sp .ne 2 .mk .na \fB\fB0\fR\fR .ad .RS 5n .rt If the expression is neither \fINULL\fR nor \fB0\fR. .RE .sp .ne 2 .mk .na \fB\fB1\fR\fR .ad .RS 5n .rt If the expression is either \fINULL\fR or \fB0\fR. .RE .sp .LP If an error occurred, \fBexpr\fR returns: .sp .ne 2 .mk .na \fB\fB2\fR\fR .ad .RS 7n .rt For invalid expressions. .RE .sp .ne 2 .mk .na \fB\fB> 2\fR\fR .ad .RS 7n .rt An error other than an invalid expression occurred. .RE .SH ATTRIBUTES .sp .LP See \fBattributes\fR(7) for descriptions of the following attributes: .sp .TS tab( ) box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Availability system/core-os _ CSI Enabled. See \fBNotes\fR. _ Interface Stability See below. _ Standard See \fBstandards\fR(7). .TE .sp .sp .LP The \fBmatch\fR, \fBsubstr\fR, \fBlength\fR, and \fBindex\fR operators are Uncommitted. Everything else is Committed. .SH SEE ALSO .sp .LP \fBbasename\fR(1), \fBecho\fR(1), \fBed\fR(1), \fBsh\fR(1), \fBIntro\fR(3), \fBattributes\fR(7), \fBenviron\fR(7), \fBregex\fR(7), \fBstandards\fR(7) .SH DIAGNOSTICS .sp .ne 2 .mk .na \fB\fBsyntax error\fR\fR .ad .RS 24n .rt Operator and operand errors. .RE .sp .ne 2 .mk .na \fB\fBnon-numeric argument\fR\fR .ad .RS 24n .rt Arithmetic is attempted on such a string. .RE .SH NOTES .SS "Operators Not CSI-Enabled" .sp .LP The following three operators are not CSI enabled. They are also not available in \fB/usr/xpg4/bin/expr\fR and \fB/usr/xpg6/bin/expr\fR: .sp .in +2 .nf \fBindex\fR \fIstring character-list\fR \fBlength\fR \fIstring\fR \fBsubstr\fR \fIstring integer-1 integer-2\fR .fi .in -2 .sp .sp .LP After argument processing by the shell, \fBexpr\fR cannot tell the difference between an operator and an operand except by the value. If \fB$a\fR is an \fB=\fR, the command: .sp .in +2 .nf example$ \fBexpr $a = '='\fR .fi .in -2 .sp .sp .LP looks like: .sp .in +2 .nf example$ \fBexpr = = =\fR .fi .in -2 .sp .sp .LP as the arguments are passed to \fBexpr\fR (and they are all taken as the \fB=\fR operator). The following works: .sp .in +2 .nf example$ \fBexpr X$a = X=\fR .fi .in -2 .sp .SS "Regular Expressions" .sp .LP Unlike some previous versions, \fBexpr\fR uses Internationalized Basic Regular Expressions for all system-provided locales. Internationalized Regular Expressions are explained on the \fBregex\fR(7) manual page. .SS "Operator Precedence Order in Other Versions" .sp .LP In previous releases of Solaris, there was a \fB/usr/ucb/expr\fR command that had a different operator precedence order than the \fBexpr\fR command described here. Also, the \fB/usr/gnu/bin/expr\fR command has its own unique operator precedence order.