Escaping ${STRING}

[Ian Gibbs]

Dear all,

I need to run this command in my make file, and capture the output to a 
variable:


python /home/igibbs/dev/OP/OpenPilot/make/scripts/version-info.py 
--path=/home/igibbs/dev/OP/OpenPilot --format='${DATE}-${TAG_OR_HASH8}${DIRTY}'

It works fine like that on the command line. The single quotes prevent the 
shell from interpreting the format string, so that the python script can use it 
as intended. Here's my make file:

.PHONY: linux_package

PROJECT_SOURCE_SHORT := $(shell basename $(ROOT_DIR))
VERSION_CMD := "python $(ROOT_DIR)/make/scripts/version-info.py 
--path=$(ROOT_DIR) --format='$${DATE}-$${TAG_OR_HASH8}$${DIRTY}'"
VERSION := $(shell $(VERSION_CMD))

linux_package:
        echo $(VERSION_CMD)


Here's the output:

address@hidden:~/dev/OP/OpenPilot/package$ make ground_package
/bin/sh: python /home/igibbs/dev/OP/OpenPilot/make/scripts/version-info.py 
--path=/home/igibbs/dev/OP/OpenPilot --format='-': No such file or directory
echo "python /home/igibbs/dev/OP/OpenPilot/make/scripts/version-info.py 
--path=/home/igibbs/dev/OP/OpenPilot --format='${DATE}-${TAG_OR_HASH8}${DIRTY}'"
python /home/igibbs/dev/OP/OpenPilot/make/scripts/version-info.py 
--path=/home/igibbs/dev/OP/OpenPilot --format='-'

It looks like VERSION_CMD is being set correctly.  However, clearly when make 
tries to set VERSION, the strings such as ${DATE} have been interpreted 
somewhere and thus disappeared (I presume it's the shell that's done this). Why 
have the single quotes no longer prevented them from being interpreted? I 
promise I've read the make manual...

Thanks for your help.
 
--
Ian Gibbs
address@hidden