How to assign the output of a command to a Makefile variable

shell makefile
fortran picture fortran · Jan 7, 2010 · Viewed 181.3k times · Source

I need to execute some make rules conditionally, only if the Python installed is greater than a certain version (say 2.5).

I thought I could do something like executing:

python -c 'import sys; print int(sys.version_info >= (2,5))'

and then using the output ('1' if ok, '0' otherwise) in a ifeq make statement.

In a simple bash shell script it's just:

MY_VAR=`python -c 'import sys; print int(sys.version_info >= (2,5))'`

but that doesn't work in a Makefile.

Any suggestions? I could use any other sensible workaround to achieve this.

Answer

Arkaitz Jimenez picture Arkaitz Jimenez · Jan 7, 2010

Use the Make shell builtin like in MY_VAR=$(shell echo whatever)

me@Zack:~$make
MY_VAR IS whatever


me@Zack:~$ cat Makefile 
MY_VAR := $(shell echo whatever)

all:
    @echo MY_VAR IS $(MY_VAR)

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