expr—evaluates arguments as an expression
expr arguments
The arguments are taken as an expression. After evaluation, the result is written to the standard output. The terms of the expression must be separated by blanks. Characters special to the shell must be escaped. Used in Bourne shell scripts for performing simple arithmetic operations.
Example A.24.
1 expr 5 + 4
2 expr 5 \* 3
3 num=0
num=`expr $num + 1`
EXPLANATION
Prints the result of 5 * 3. The asterisk is protected from shell expansion. After assigning 0 to variable num, the expr command adds 1 to num and result is assigned to num.
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