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EXPR(1)                                  BSD General Commands Manual                                 EXPR(1)

NAME
     expr -- evaluate expression

SYNOPSIS
     expr expression

DESCRIPTION
     The expr utility evaluates expression and writes the result on standard output.

     All operators are separate arguments to the expr utility.  Characters special to the command inter-preter interpreter
     preter must be escaped.

     Operators are listed below in order of increasing precedence.  Operators with equal precedence are
     grouped within { } symbols.

     expr1 | expr2
             Returns the evaluation of expr1 if it is neither an empty string nor zero; otherwise, returns
             the evaluation of expr2.

     expr1 & expr2
             Returns the evaluation of expr1 if neither expression evaluates to an empty string or zero;
             otherwise, returns zero.

     expr1 {=, >, >=, <, <=, !=} expr2
             Returns the results of integer comparison if both arguments are integers; otherwise, returns
             the results of string comparison using 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.

     expr1 {+, -} expr2
             Returns the results of addition or subtraction of integer-valued arguments.

     expr1 {*, /, %} expr2
             Returns the results of multiplication, integer division, or remainder of integer-valued argu-
             ments.

     expr1 : expr2
             The ``:'' operator matches expr1 against expr2, which must be a regular expression.  The regu-lar regular
             lar expression is anchored to the beginning of  the string with an implicit ``^''.  expr
             expects "basic" regular expressions, see re_format(7) for more information on regular expres-sions. expressions.
             sions.

             If the match succeeds and the pattern contains at least one regular expression subexpression
             ``\(...\)'', the string corresponding to ``\1'' is returned; otherwise the matching operator
             returns the number of characters matched.  If the match fails and the pattern contains a regu-lar regular
             lar expression subexpression the null string is returned; otherwise 0.

     Parentheses are used for grouping in the usual manner.

EXAMPLES
     1.   The following example adds one to the variable a.
                a=`expr $a + 1`

     2.   The following example returns the filename portion of a pathname stored in variable a.  The //
          characters act to eliminate ambiguity with the division operator.
                expr //$a : '.*/\(.*\)'

     3.   The following example returns the number of characters in variable a.
                expr $a : '.*'

DIAGNOSTICS
     The expr utility exits with one of the following values:
     0       the expression is neither an empty string nor 0.
     1       the expression is an empty string or 0.
     2       the expression is invalid.

STANDARDS
     The expr utility conforms to IEEE Std 1003.2 (``POSIX.2'').

BSD                                             July 3, 1993                                             BSD