make.txt

# make
-f  Makefile
-B  // always rebuild target
-j  n // number of jobs to be run in parallel

# variables
$@  // target
$*  // match pattern in pattern rule
target-%:
  echo $* // target-X prints X
$<  // first prerequisite
$+, $^  // all prerequisites
$(@D), $(@F)  // directory and filename of $@
$(<D), $(<F)  // directory and filename of $<
$(+D), $(+F)  // directory and filename of $+
$$HOME  // escape/mask shell variable
\:  // escape colon
$HOME // environment variables become Make variables


## assignments
x = value
x ?= value  // only if not defined
x := value  // overwrite
target: x = value // target specific variable

# multiple commands per line
seqmonk: txt
	mkdir -p seqmonk && \
	for infile in $$(ls txt/*txt); do \
		outfile=seqmonk/$$(basename $$infile); \
		./txt_to_seqmonk.py $$infile > $$outfile; \
	done

# functions
$(patsubst RSC_%,cell_%, RSC_1 RSC_2) // cell_1 cell_2
$(RSC_1 RSC_2:RSC_%=cell_%) // same as before; no space around ':'!
$(subst what,by,string) // substitute substring
$(filter-out %.txt,vars)  // filter out by pattern

$(wildcard dir/*.dir) // glob files; ls dir/*.dir
$(dir /dir/file.txt)  // /dir
$(notdir /dir/file.txt) // file.txt
$(suffix /dir/file.txt) // .txt
$(basename /dir/file.txt)  // /dir/file; -> remove suffix
$(addprefix prefix, list) // a b, .txt -> a.txt b.txt
$(addsuffix suffix, list)
$(shell ls) // shell command

# control structures
## if
$(if var,true,false)  // if var not empty
$(if ,true,false) // -> true
## loops
$(foreach var,list,foo $(var) bar)  // loop over list
## functions
reverse = $(2) $(1) // reverse 1st and 2nd arg; $(0) is name of function
$(call reverse,word1,word2) // $(call NAME,arg1,arg2)
## example
parse_k = $(shell python  -c 'import re; print(re.search("_k(\d+)", "$(1)").group(1))')
k = $(call parse_k,file_k123_w100.h5)
## assert
$(error Message)  // stop with error message
$(warning Message)  // stop with error message


# pattern rule
%.o: %.c
  gcc -o $@ $<

## different directories
$(a_dir)/%.a:
  cmd
$(b_dir)/%.b: $(a_dir)/%.a
  cmd

## wildcards
%.o: $(dir)/*%*.c
  NOTE: $(wildcard $(dir)/*%*.c) does not work! % not in functions!

# suffix rule // deprecated
.c.o:
  gcc -o $@ $<

# static pattern rule
list_targets : pattern : pattern_pre
  apply command to each target that matches pattern individually
file1.h5 file2.h5 file3.h5: %:
  echo $@ // file1.h5; file2.h5; file3.h5
File1.h5 file2.h5 file3.h5: F%:
  echo $@ // file2.h5; file3.h5 --> File1.h5 filtered out

objects = foo.o bar.o
$(object): %.o : %.c
  gcc -c $@ $^

# order-only prerequisites
* are always executed before all other prerequisites
target: pre | order-only

# print value of variable
print-var:
  echo $($*)

# supress echo of command
target:
  @command