GNU Make - Set a flag if multiple files exist

Question

In my Makefile, I check if a file exists, and execute different code depending on the result of that check.

Previously, there was only one relevant file, OUTLIB_CACHE.

OUTLIB_CACHE := filename
OUTLIB_CACHE_EXITS := $(shell if [ -f $(OUTLIB_CACHE) ]; then echo "1"; fi;)
ifneq ($(OUTLIB_CACHE_EXISTS),1)    
    # do something
endif

Now I am introducing a second relevant file, storing both of the file names in a list:

OUTLIB_CACHE_LIST := filename1 filename2

I want to set the OUTLIB_CACHE_EXISTS flag to true if and only if all the files in OUTLIB_CACHE_LIST exist. What would be the best way to do this?

Answer 1

You could substitute each element of OUTLIB_CACHE_LIST with a command, then execute the resulting commands in a shell:

OUTLIB_CACHE_MISSING := $(shell $(patsubst %,test -e "%" || echo missing;,$(OUTLIB_CACHE_LIST)))

If all the members exist, then the output of the shell command will be empty, else it will contain one word for each missing file. You can test for emptiness:

ifneq ($(OUTLIB_CACHE_MISSING),)    
    # do something
endif

---

If you want to know which files are missing, you can't just replace ! with %, because patsubst only replaces the first % it finds. Instead, you could use foreach:

OUTLIB_CACHE_MISSING := $(shell $(foreach f,$(OUTLIB_CACHE_LIST),test -e "$f" || echo "$f";))

---

Putting this all together in a testable example:

OUTLIB_CACHE_LIST := /etc /bin
#OUTLIB_CACHE_LIST += /nonexistent

OUTLIB_CACHE_MISSING := $(shell $(foreach f,$(OUTLIB_CACHE_LIST),test -e "$f" || echo "$f";))

.PHONY: all

all:
ifneq ($(OUTLIB_CACHE_MISSING),)
    false "$(OUTLIB_CACHE_MISSING)"
else
    true "No missing files"
endif

Uncomment the second line to select the first branch of the if.

---

N.B. You wanted to know whether the files exist, so I've used test -e rather than -f or -r. You'll know which test is actually appropriate for your case...

Answer 2

There is no need to use shell functions to test for the existence of multiple files in make. I use the following construct to make make output decent error messages for a very convoluted makefile. I presume you can adopt it to your needs if need be. The original idea (probably) comes from https://stackoverflow.com/a/20566812/1905491.

$(foreach p,$(ALL_INCLUDES),$(if $(wildcard $(p)),,$(info $(p) does not exist!) $(eval err:=yes)))
$(if $(err),$(error Aborting),)

Answer 3

Simply define OUTLIB_CACHE_EXISTS as follows

OUTLIB_CACHE_EXISTS := $(shell if ls $(OUTLIB_CACHE_LIST) >/dev/null 2>&1; then echo "1"; fi)

Answer 4

This should work

ifeq ($(OUTLIB_CACHE_LIST),$(wildcard $(OUTLIB_CACHE_LIST)))
# do something
endif