Linux Journal - September 2011

when you are using suffix rules (discussed later in this article).

.DEFAULT — if you have a bunch of targets that use the same set of commands, you may consider using the .DEFAULT target. It is used to specify the commands to be executed when no rule is found for a target.

.PRECIOUS — all dependencies of the .PRECIOUS target are preserved should make be killed or interrupted.

.INTERMEDIATE — specifies which targets are intermediate, or temporary, files. Upon completion, make will delete all intermediate files before terminating.

.SECONDARY — this target is similar to .INTERMEDIATE, except that these files will not be deleted automatically upon completion. If no dependencies are specified, all files are considered secondary.

.SECONDEXPANSION — after the initial read-in phase, anything listed after this target will be expanded for a second time. So, for example:

.SECONDEXPANSION: ONEVAR = onefile TWOVAR = twofile myfile: $(ONEVAR) $$(TWOVAR)

will expand to:

.SECONDEXPANSION: ONEVAR = onefile TWOVAR = twofile myfile: onefile $(TWOVAR)

after the initial read-in phase, but because I specified .SECONDEXPANSION, it will expand everything following a second time:

.SECONDEXPANSION: ONEVAR = onefile TWOVAR = twofile myfile: onefile twofile

I’m not going to elaborate on this here, because this is a rather complex subject and outside the scope of this article, but you can find all sorts of .SECONDEXPANSION goodness out there on the Internet and in the GNU manual.

.DELETE_ON_ERROR — this target will cause make to delete a target if it has changed and any of the associated commands exit with a nonzero status.

.IGNORE — if an error is encountered while building a target list as a dependency of .IGNORE, it is ignored. If there are no dependencies to .IGNORE, make will ignore errors for all targets.

.LOW_RESOLUTION_TIME — for some reason or another, if you have files that will have a low-resolution timestamp (missing the subsecond portion), this target allows you to designate those files. If a file is listed as a dependency of .LOW_RESOLUTION_TIME, make will compare times only to the nearest second between the target and its dependencies.