Mastering Linux Shell Scripting - Second Edition

Parameter manipulation

Perhaps a little more useful to us in scripting is the C-style parameter manipulation that we can include using the double parenthesis. We can often use this to increment a counter within a loop and also put a limit on the number of times the loop iterates. Consider the following command:

$ COUNT=1$ (( COUNT++ ))echo $COUNT

Within this example, we first set COUNT to 1 and then we increment it with the ++ operator. When it is echoed in the final line, the parameter will have a value of 2. We can see the results in the following screenshot:

We can achieve the same result in longhand by using the following syntax:

$ COUNT=1 ...