Question

in general i will use expr inside shell scripts for doing arithmetic operations.

is there a way where we can come up with arithmetic operation in a shell script without using expr?

Answer 1

Did you tried to read “man ksh” if you’re using ksh?

“man bash”, for example, has enough information on doing arithmetics with bash.

the command typeset -i can be used to specify that a variable must be treated as an integer, for example typeset -i MYVAR specifies that the variable MYVAR is an integer rather than a string. Following the typeset command, attempts to assign a non integer value to the variable will fail:

   $ typeset -i MYVAR
   $ MYVAR=56
   $ echo $MYVAR
   56
   $ MYVAR=fred
   ksh: fred: bad number
   $

To carry out arithmetic operations on variables or within a shell script, use the let command. let evaluates its arguments as simple arithmetic expressions. For example:

   $ let ans=$MYVAR+45
   echo $ans
   101
   $

The expression above could also be written as follows:

   $ echo $(($MYVAR+45))
   101
   $

Anything enclosed within $(( and )) is interpreted by the Korn shell as being an arithmetic expression