18 Dec

Using M4 Command

This command takes an input file and substitutes strings inside it with the parameters passed, similar to substituting for variables. For example, here is an input file:

$ cat temp
The COLOR fox jumped over the TYPE fence.

Were you to substitute the strings “COLOR” by “brown” and “TYPE” by “broken”, you could use:

$ m4 -DCOLOR=brown -DTYPE=broken temp
The brown fox jumped over the broken fence.

Else, if you want to substitute “white” and “high” for the same:

$ m4 -DCOLOR=white -DTYPE=high temp
The white fox jumped over the high fence.