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EXPR(1) 	       DragonFly 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 and operands must be passed as separate arguments. Several of the operators have special meaning to command interpreters and must therefore be quoted appropriately. All integer operands are interpreted in base 10. Arithmetic operations are performed using signed integer math. Operators are listed below in order of increasing precedence; all are left-associative. Operators with equal precedence are grouped within { } symbols. expr1 | expr2 Return the evaluation of expr1 if it is neither an empty string nor zero; otherwise, returns the evaluation of expr2. expr1 & expr2 Return the evaluation of expr1 if neither expression evaluates to an empty string or zero; otherwise, returns zero. expr1 {=, >, >=, <, <=, !=} expr2 Return 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 Return the results of addition or subtraction of integer-valued arguments. expr1 {*, /, %} expr2 Return the results of multiplication, integer division, or remainder of integer-valued arguments. 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 ``^''. 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 returns the number of characters matched. If the match fails and the pattern contains a regular expression subexpression the null string is returned; otherwise 0. Parentheses are used for grouping in the usual manner.

EXIT STATUS

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.

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 : '.*'

SEE ALSO

sh(1), test(1)

STANDARDS

The expr utility conforms to IEEE Std 1003.2 (``POSIX.2''). DragonFly 3.9 April 10, 2013 DragonFly 3.9