insomniacjunkie insomniacjunkie - 1 year ago 146
Perl Question

Script to Find CPP Macro Object and Replace Token

Okay, I have tried to do this in Perl and have had little to no success...

Inside of a .cpp file I have the following text...

#define VARIABLE_A 32

And I wish to replace this with some other number

#define VARIABLE_A 123

I would like to be able to run this through my command-line such as:

change_variable_a 123

What is the easiest way to achieve this? BASH or Perl preferred.

The code I have now is garbage. I am going about it completely wrong trying to pass parameters through a bash script into a perl one-liner.

Okay here is what I have.

perl -MPOSIX -pe's/(\d+)/@ARGV[0]/e if /define\s+VARIABLE_A\s+\d+/' file.h > file.h.2
mv -f file.h.2 file.h

Answer Source

When you recompile, you can use the -D option to set a value on the command line (at least in gcc and clang; presumably others). So the simplest solution is to just define VARIABLE_A on the command line.

gcc -D VARIABLE_A=123

If you want to have a default, you just need to have something in your code to define VARIABLE_A when it hasn't been set on the command line.

#ifndef VARIABLE_A
#define VARIABLE_A 32
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