Note: The following material was developed by Claude Cantin of the Research Computing Support Group of the National Research Council of Canada, and is used with his permission.

expr: Doing Arithmetic

expr is used to perform arithmetic manipulations. Five functions can be used:

+

addition.

-

subtraction.

*

multiplication.

/

division.

%

remainder.

Here is an example that uses all of them:

    #!/bin/sh
    if test $# -lt 2 -o $# -gt 2
    then
        echo Must provide two and only two parameters.
        exit 1
    fi
    SUM=`expr $1 + $2`
    DIFF=`expr $1 - $2`
    PRODUCT=`expr $1 "*" $2`
    QUOTIENT=`expr $1 / $2`
    REM=`expr $1 % $2`
    TOTAL=`expr $SUM + $DIFF + $PRODUCT + $QUOTIENT + $REM`
    echo The sum is $SUM.
    echo The difference is $DIFF.
    echo The product is $PRODUCT.
    echo The quotient is $QUOTIENT.
    echo The remainder is $REM.
    echo The total sum of all these numbers is $TOTAL.
    exit 0

NOTES:

• The entire expr line is enclosed within back quotes. Normally, the output of expr is the standard output. Including the back quotes will assign the result to a variable.
• The * is between double quotes. If it was not, the shell would interpret it as the wildcard character.
• expr is a shell feature found in both the Bourne and C shells.