CODEWITHSUNDEEP
perlmakefilegnu-make
chris yo
chris yo

Reputation: 1277

How can I store output string to a variable AND display in console

I have a perl script that prints a message. This script is being called by GNU make. In my GNU make, I want to display the message printed out by the script AND store it in a variable also.

I'm doing it this way. 

 result=`$(PERL) parse.pl report.log` #parse the report
 echo $(result) #echo the message here
 ifneq ($(strip $$(result)),) #check if message is empty
   #if not empty, search for filepath string pattern and exit
   echo filepath
   exit 1
 endif

But it is not displaying the string message from parse.pl.

Upvotes: 0

Views: 260

Answers (2)

MadScientist
MadScientist

Reputation: 100806

The critical thing to keep in mind with make is first, that the entire makefile is parsed before any rules are run, and second a makefile has two completely distinct syntaxes in it: makefile syntax for most of it, and shell syntax for the recipes. The shell syntax is run by the shell, not by make: make just starts a shell, hands over the recipe, and waits for the shell to exit to see if it worked or not.

As a result of this you CANNOT combine make constructs like ifeq with shell commands and their results: it cannot work because all the make constructs are parsed first, while the makefile is being read in, and the shell commands are not run until much later, when the target is to be built.

In your case you need to write the entire thing in shell syntax, because you want things to depend on the shell invocation.

So, like this:

foo:
        result=`$(PERL) parse.pl report.log`; \
        echo $$result; \
        if [ "$$result" = "" ]; then \
            echo filepath; \
            exit 1; \
        fi

Note how each line ends with a backslash, so it's appended to the previous line instead of being a separate line: make runs each separate line in a different shell.

Alternatively if you have a new-enough GNU make you can use the one shell feature:

.ONESHELL:
foo:
        result=`$(PERL) parse.pl report.log`
        echo $$result
        if [ "$$result" = "" ]; then
            echo filepath
            exit 1
        fi

Upvotes: 0

ysth
ysth

Reputation: 98388

You are capturing into a shell variable, but then trying to echo a makefile variable (and even if you tried to echo the shell variable, that wouldn't work because make runs each line in a separate shell process).

Changing it to echo the shell varible and all to run in one shell should work:

foo:
    result=`$(PERL) parse.pl report.log`; \
    echo $$result

but whatever you later need to do to use the captured result would also need to be in the same shell execution.

Apparently you can capture into a makefile variable too, which may be more convenient:

foo:
    $(eval result := $(shell $(PERL) parse.pl report.log))
    echo $(result)

Upvotes: 1

Related Questions