EXPR(1)                 COMMAND REFERENCE                 EXPR(1)



NAME
     expr - evaluate arguments as an expression

SYNOPSIS
     expr arg ...

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.  Expressions are
     expected to be integers and strings. Floating point numbers
     are not supported.

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

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

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

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

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

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

     expression : expression
        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).  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 expression expression
        This is a synonym for the : operator.

     substr string start length



Printed 4/6/89                                                  1

EXPR(1)                 COMMAND REFERENCE                 EXPR(1)



        The substring operator yields the portion of string
        beginning at position start that is a maximum of length
        characters long.  start must be an expression which
        yields a positive integer, and length must be an
        expression which yields a non-negative integer.

     length expression
        The length operator yields the length of the string
        expression.

     index string character-list
        The index operator yields the position of the first
        occurrence of any character in character-list found in
        string.

     ( expression )
        parentheses for grouping.

EXAMPLES
     To add 1 to the Shell variable a (where a is already set) :

          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
     `/' (this is partially equivalent to basename(1) ):

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

     Note the quoted Shell metacharacters.

     This example prints the portion of the home directory name
     following the first '/' character after the first character
     in the name.  (Note the escaped /, which would normally mean
     division.):

          expr substr \
               \( substr $HOME 2 1024 \) \
               \( index \( substr $HOME 2 1024 \) '\/' \) + 1 \
               1024

     If $HOME is /usr/guest , the above expression would print
     'guest'.

RETURN VALUE
     [0]            The expression is neither null nor '0'.

     [1]            The expression is either null or '0'.

     [2]            The expression contains errors.





Printed 4/6/89                                                  2

EXPR(1)                 COMMAND REFERENCE                 EXPR(1)



CAVEATS
     The strings substr, index, length, and match may appear only
     as operators, and not as strings. Therefore, an expression
     like 'substr : [ubs]*' results in a syntax error.

SEE ALSO
     basename(1), sh(1sh), and test(1sh).
















































Printed 4/6/89                                                  3

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na:240,94;
sy:334,178;
de:512,2790;3614,952;
ex:4566,935;
rv:5501,297;
ca:6110,308;
se:6418,208;
%%index%%000000000130