Re: Original stdout inside the $(shell ...) function

[Basin Ilya]

Hi David.
I'll try to explain what I want better. The evaluation should print a 
diagnostic message and it should be printed to a file descriptor that was the 
stdout of the make program when it was started. That is, when you run the make 
command with output redirected to /dev/null, the diagnostic message should be 
suppressed as well, because it's not an error or warning:

    $ make >/dev/null
    $

    $ make
    blah blah
    finding SQLFILES...
    blah blah
    ...
    $


Currently my message is printed to stderr and therefore always printed:

    $ make >/dev/null
    finding SQLFILES...
    $

The problem is with make, not with the shell programming. Here's an equivalent 
of my current variable assignment, rewritten for shell:

    SQLFILES=`>&2 echo finding SQLFILES... && cd "${srcdir}" && find . -name 
"*.sql"`

And this is how my problem would be solved, if it was shell:

    exec 4>&1
    SQLFILES=`>&4 echo finding SQLFILES... && cd "${srcdir}" && find . -name 
"*.sql"`

The message is printed to the fd "4", which is the original stdout, while 
everything else is printed to fd "1", which is the stdout redirected by the 
parent shell to perform the assignment.

Unfortunately, I can't find anything like "exec 4>&1" (globally) in Make. The 
only workaround I can think of is calling make from a wrapper, which performs 
the redirection.


On 10.04.2018 17:25, David Boyce wrote:
> This looks like a basic shell programming issue, not a make problem at all. 
> Try pulling this logic out of make and running it directly in the shell; if 
> it behaves correctly there but not when plugged back into make, then you'll 
> have a make question. This looks more like a scoping problem. Here is 
> (effectively) your original script:
> 
> % sh -c ">&2 echo finding SQLFILES... && date" 1>1 2>2
> 
> % head 1 2
> ==> 1 <==
> Tue Apr 10 07:18:56 PDT 2018
> 
> ==> 2 <==
> finding SQLFILES...
> 
> And here's a variant with different scoping: 
> 
> % sh -c "(echo finding SQLFILES... && date) 1>&2" 1>1 2>2
> 
> % head 1 2
> ==> 1 <==
> 
> ==> 2 <==
> finding SQLFILES...
> Tue Apr 10 07:19:09 PDT 2018
> 
> It's not clear to me exactly what you want but this should illustrate that 
> the issue is shell redirection.
> 
> Personally I prefer techniques that let the shell handle verbosity instead of 
> typing ad-hoc messages:
> 
> SQLFILES := $(shell set -x; cd "$(srcdir)" && find . -name "*.sql")
> 
> David
> 
> On Tue, Apr 10, 2018 at 3:07 AM, Basin Ilya <address@hidden 
> <mailto:address@hidden>> wrote:
> 
>     Hi. I want to print a diagnostic message whenever my shell expression is 
> evaluated. Currently, I have the following line in my makefile:
> 
>         SQLFILES := $(shell >&2 echo finding SQLFILES... && cd "$(srcdir)" && 
> find . -name "*.sql")
> 
>     As you can see, the message "finding SQLFILES..." is printed to stderr, 
> but I want the original stdout instead. Does GNU Make make it available as 
> some other fd, say, "4"?
> 
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