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EXPR(1) OpenBSD Reference 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. Char- acters special to the command interpreter 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 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. expr1 {+, -} expr2 Returns the results of addition or subtraction of integer-valued arguments. expr1 {*, /, %} expr2 Returns the results of multiplication, integer division, or re- mainder 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 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, returns 0. Parentheses are used for grouping in the usual manner. EXAMPLES $ a=`expr $a + 1` Add 1 to the variable a. $ expr //$a : '.*/\(.*\)' Return the filename portion of a pathname stored in variable a. The `//' characters act to eliminate ambiguity with the division operator. $ expr $a : '.*' Return the number of characters in variable 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. >2 An error occurred (such as memory allocation failure). SEE ALSO test(1) STANDARDS The expr utility conforms to IEEE Std 1003.2 (``POSIX.2''). OpenBSD 3.4 July 3, 1993 2
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | DIAGNOSTICS | SEE ALSO | STANDARDS
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