GNU make: Extracting argument to -j within Makefile

Question

I've been searching for an hour, and this information appears to be nowhere...

I'd like to be able to extract (and possibly use) the number of requested make "jobs," as passed via the -j option, or by Make itself in the case of sub-makes, in the Makefile.

The most promising thing I've seen so far is the $(MAKEFLAGS) variable, but on my system (if I do, say, make -j2) the contents of this variable are only "--jobserver-fds=3,4 -j". Is there any way to get the actual number of jobs passed with -j?

Answer 1

Actually there is a way to implement this completely inside your makefile on *nix.

MAKE_PID := $(shell echo $$PPID) JOB_FLAG := $(filter -j%, $(subst -j ,-j,$(shell ps T | grep "^\s*$(MAKE_PID).*$(MAKE)"))) JOBS     := $(subst -j,,$(JOB_FLAG)) 

ps, grep also need to be installed, but it is almost a given. It can be further improved to handle --jobs too

A version using regex and supporting --jobs, as requested in the comments:

MAKE_PID := $(shell echo $$PPID) JOBS := $(shell ps T | sed -n 's/.*$(MAKE_PID).*$(MAKE).* \(-j\|--jobs=\) *\([0-9][0-9]*\).*/\2/p')