Make Utiltiy Hints

From SnOwy - Ed's Wiki Notebook

keywords: makefile

Contents 1 Case Sensitivity 2 Concurrent execution (parallel) 3 Uninformative Error Messages 4 Automatic variables 5 Andre's help

Case Sensitivity

• make is case sensitive despite the underlying file system and operating system.

Concurrent execution (parallel)

make -j3

Causes make to build three concurrent dependency graphs.

Uninformative Error Messages

makefile:4: *** missing separator. Stop.

Where "4" can be any line number in the makefile-- this means that the make utility was expecting tab characters but instead got spaces.

Automatic variables

$@ -- the first target
$< -- the first prerequisite
$+ -- all the prerequisites listed in precise order; duplications are retained

Andre's help

This allows a parameter substitution -- in this case, the binary is called "dssp", the targets are ".dssp" files, and the inputs are ".pdb" files.

Note: patsubst is a builtin function, so is wildcard; gnumake's built-in functions take the form "$(<function_name> <args <, ...>>)".

all: $(patsubst %.pdb, %.dssp, $(wildcard *.pdb))

%.dssp: %.pdb
	dssp $< $@

.PHONY: all

#Thanks to Andre's Scary Magical Make Knowledge.
# $< is the first prerequisite, in this case it's a %.pdb in *.pdb
# $@ is the target, in this case it's a %.dssp in *.dssp

This one allows one to pass three parameters-- the first parameter indicates inputs, the second and third are targets.

all: $(patsubst dssp/%.dssp, fasta/%.fasta, $(wildcard dssp/*.dssp))\
	$(patsubst dssp/%.dssp, fasta/%.fastasse, $(wildcard dssp/*.dssp))

fasta/%.fasta fastasse/%.fastasse: dssp/%.dssp
	python dssp2fasta.py dssp/$*.dssp fasta/$*.fasta fastasse/$*.fastasse

.PHONY: all

This example corresponds to using ImageMagick's convert commandline utility ...

all_convert: $(patsubst %.png, %.eps, $(wildcard *.png))

%.eps: %.png
	convert $< $@

It should be a bit easier to understand than earlier examples (since there are fewer things happening).

• this makefile creates one eps for every png inside the current directory when run

Another imagemagick example -- this time including subdirectories ...

all_convert: $(patsubst colourimages/%.png, greyimages/%.png, $(wildcard colourimages/*.png))

greyimages/%.png: colourimages/%.png
	convert $< -colorspace Gray -alpha off $@

In this example, imagemagick is called to convert colour images to grey images

• notice that the file extension stays the same, but make utility respects the directory structure