Replacing text with sed

Question

I have in my file a line of this kind

    integer, parameter ::  L = 2   !Size of the system

Where the number 2 can be any integer number. I want to find this line using sed and replace the value of the number with another one.

I tried:

$ L=5
$ sed -i '/L = /c\integer, parameter ::  L = $L   !Size of the system' moduleselfcons.f90

but in my modified file I have at the end:

integer, parameter ::  L = $   !Size of the system

and not:

integer, parameter ::  L = 5   !Size of the system

What is the problem?

Answer 1

You should use double quotes (") instead of single quotes (').

But I think you can shorten the expression:

L=5
sed "s/L = [0-9]*/L = $L/" file

If it is your desired output add the -i flag for in-place editing.