Re: $(shell ..) testing for the exit value

[John Graham-Cumming]

Abramovitz, Norman wrote:
> When using the $(shell ..) function, is there a way to retrieve the 
> shell's exit value?  The output from the invocation is parsed by
> foreach and eval so I cannot return a string as an exit code.  The
> following two lines are executed outside any rules.

No, but you could write your own $(shell) wrapper that gives you the 
exit code.  For example,

    myshell = $(shell echo `$1` $$?)

$(myshell command) returns the output of command with the exit code of 
command appended.  For example

    $(call myshell,echo hello john)

would return

    hello john 0

or

    $(call myshell,exit 3)

would return

    3

If you want to get really fancy you could make myshell return only the 
values return by the command and store the exit code in a variable. 
Here I use the GNU Make Standard Library and require GNU Make 3.80 since 
I'll use $(eval):

    include gmsl

    __myshell = $(shell echo `$1` $$?)

    myshell = $(eval __result := $(call __myshell,$1))
    $(eval MYSHELL_RESULT := $(call last,$(__result)))
    $(call chop,$(__result))

So doing $(call myshell,command) works just like $(shell command) but 
the return code of the command is stored in MYSHELL_RESULT.  (Note I've 
only tested all this with bash and zsh).

John.
--
John Graham-Cumming
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