Shell – Convert character to Number

Issue

I made a small shell script in which thanks to commands: sort, cut, awk,
I could retrieve the largest GID group of my system, and saving it in a variable C.
I would like to increment this GID for other use, but the result is false.

If GID is returned is c = 5000, this is what I did next:

echo $ ((c +1))

but I get the result as "1".
I would therefore ask if the GID recovered is seen as a string?
If yes how can I do to convert people?

Solution

Hello you can use this:

[tmpfs]$ A=$(id -g)

[tmpfs]$ echo $A
500

[tmpfs]$ ((A++))

[tmpfs]$ echo $A
501

[tmpfs]$

Note

Thanks to jipicy for this tip on the forum.