Sometimes you need direct make to progress through various phases which may not have a particular file target associated with them. For example the first step might be to extract a compressed tarball of data and run a script over it in preparation for compiling that data into something else. Equally you might need to patch some files or maybe download some data. The general idiom to accomplish this sort of thing is the stamp file.

The general principle is to make a phony target that depends on a file called target-stamp. The target-stamp target can then do what it needs to do and simply create a dummy file via touch. This file indicates to make that the phase is complete, and targets that depend on this phase being complete can now depend on the stamp file. A small example follows

all: final

.PHONY: prepare clean

final: prepare
        # run build process

prepare: prepare-phase1-stamp prepare-phase2-stamp

prepare-phase1-stamp:
        # untar data or something
        touch $@

prepare-phase2-stamp: prepare-phase1-stamp
        # run a script or do something else
        touch $@

clean:
        rm -f *-stamp

One place you may notice extensive use of this is the -stamp files in the /debian directory of packages built with CDBS.

posted at: Thu, 27 Sep 2007 11:46 | in /linux/tips | permalink | add comment (2 others)