A makefile that says how to recompile a program can be used in more
than one way. The simplest use is to recompile every file that is out
of date. Usually, makefiles are written so that if you run
make with no arguments, it does just that.
But you might want to update only some of the files; you might want to use a different compiler or different compiler options; you might want just to find out which files are out of date without changing them.
By giving arguments when you run
make, you can do any of these
things and many others.
The exit status of
make is always one of three values:
The exit status is zero if
make is successful.
The exit status is two if
make encounters any errors.
It will print messages describing the particular errors.
The exit status is one if you use the ‘-q’ flag and
determines that some target is not already up to date.
See Instead of Executing Recipes.