I have a poorly designed build script that always overwrites files that it shouldn't; if I edit these files and then run the script, it overwrites their content and, thus, the build fails.
How can I "lock" these files so that the overwrite fails?
I've tried opening them in editors (vi(m), gedit) but overwrite works regardless?
Fixing your poorly designed script seems like the best option. Any other thing may be too intrusive.
However, in some situations it may not be possible. If the script is very big and complicated it may be too much work.
An intermediate solution would be to have a user with the lowest privileges, and have the build script switch to that user in the beginning. The file permissions of the system will do the rest...
set -Cto it.set -Conly prevents overwriting by redirection (>). It would not preventgcc a.c -o afrom overwritinga. And the script can overwrite files bymv x a, so that is another thing. All in all, better to give us more details.man - a chmodand use the+i(immutable) flag.