EXPR(1)

NAME
expr - evaluate arguments as an expression

SYNOPSIS
expr arguments ...

DESCRIPTION
The arguments are taken as an expression. After evaluation, the result is written on the standard output. Each token of the expression is a separate argument.

The operators and keywords are listed below. The list is in order of increasing precedence, with equal precedence operators grouped.

expr | expr
    yields the first expr if it is neither null nor `0', otherwise yields the second expr.

expr & expr
    yields the first expr if neither expr is null or `0', otherwise yields `0'.

expr relop expr
    where relop is one of < <= = != >= >, yields `1' if the indicated comparison is true, `0' if false. The comparison is numeric if both expr are integers, otherwise lexicographic.

expr + expr
    expr - expr
    addition or subtraction of the arguments.

expr * expr
    expr / expr
    expr % expr
    multiplication, division, or remainder of the arguments.

expr : expr
    The matching operator compares the string first argument with the regular expression second argument. Regular expression syntax is the same as that of ed(1); /usr/local/heirloom/usr/5bin/expr uses simple regular expressions, /usr/local/heirloom/usr/5bin/posix/expr, /usr/local/heirloom/usr/5bin/posix2001/expr, and /usr/local/heirloom/usr/5bin/s42/expr use basic regular expressions. The \(...\) pattern symbols can be used to select a portion of the first argument. Otherwise, the matching operator yields the number of characters matched (`0' on failure).

match expr expr
    Same as expr : expr.

( expr )
    parentheses for grouping.

string
    Yields itself unless it is part of a larger expression. With /usr/local/heirloom/usr/5bin/posix/expr and /usr/local/heirloom/usr/5bin/posix2001/expr, all strings that form valid decimal numbers are converted to the canonical form.

The following operators are supported only by /usr/local/heirloom/usr/5bin/s42/expr or if the SYSV3 environment variable is set:

length string
    Returns the number of characters in string.

substr string index count
    Returns a string that consists of count characters beginning at position index of string (starting at 1).

index string set
    Returns the index in string (starting at 1) of the first occurrence of one of the characters in set, or 0 if no character is found.

ENVIRONMENT VARIABLES

LANG, LC_ALL
    See locale(7).

LC_COLLATE
    Sets the collation sequence for string comparison, and for range expressions, equivalence classes, and collation symbols in basic regular expressions.

LC_CTYPE
    Determines the mapping of bytes to characters in regular expressions, for the match, length, substr, and index operators, and the availability and composition of character classes in basic regular expressions.

SYSV3
    Enables some additional operators as described above.

EXAMPLES

To add 1 to the Shell variable a:

    a=`expr $a + 1`

To find the filename part (least significant part) of the pathname stored in variable a, which may or may not contain `/':

    expr "$a" : '.*/\(.*\)' '|' "$a"

Note the quoted Shell metacharacters. Also note that this example generates wrong results if the result of the substitution is `0' or if `$a' equals one of the expr operators. Be sure that your code avoids such problems and use basename(1) if to actually cut out filename parts.

SEE ALSO
ed(1), sh(1), test(1)

DIAGNOSTICS
Expr returns the following exit codes:

    0    if the expression is neither null nor `0',
    1    if the expression
is null or `0',
    2    for invalid expressions.

NOTES
Integers are treated as 64-bit, 2's complement numbers.