expr(1) — UTek W2.3



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.




Printed 10/17/86                                                1



EXPR(1)                 COMMAND REFERENCE                 EXPR(1)



     substr string start length
         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






Printed 10/17/86                                                2



EXPR(1)                 COMMAND REFERENCE                 EXPR(1)



     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.

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), test(1sh).






































Printed 10/17/86                                                3

%%index%%
na:72,78;
sy:150,118;
de:268,2540;2952,1013;
ex:3965,819;4928,94;
rv:5022,252;
ca:5274,280;
se:5554,166;
%%index%%000000000138

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