Re: suppressing shell error output

[Martin Sebor]

Paul D. Smith wrote:
> %% Martin Sebor <address@hidden> writes:
>
>   ms> Is there an efficient way to suppress the error output of the shell
>   ms> in the $(shell) function?
>
> Make can't do it.  You can only do it from within the shell script
> you're invoking.

There's no way the script could do it if it doesn't exist :) Or
did you mean that I should wrap the command foo in a script that
is guaranteed to exist and invoke it instead? That would work but
it's just as inefficient as my $(shell /bin/sh) hack: it causes
two processes to be executed instead of just one.

It seems that make should provide a mechanism to do it. After all,
it lets users decide what to do with the shell error output in all
other cases.

Looking at func_shell() in function.c, the block on lines 1641-1646
looks like the output I'm trying to suppress. It should only be a
matter of coming up with suitable syntax to let callers specify what
to do with the output. Since the @ character is used to suppress
command output elsewhere, perhaps make could reuse is here as well.
How about $(@shell)?

  1636        /* The child_handler function will set 
shell_function_completed
  1637           to 1 when the child dies normally, or to -1 if it
  1638           dies with status 127, which is most likely an exec 
fail.  */
  1639
  1640        if (shell_function_completed == -1)
  1641          {
  1642            /* This most likely means that the execvp failed,
  1643               so we should just write out the error message
  1644               that came in over the pipe from the child.  */
  1645            fputs (buffer, stderr);
  1646            fflush (stderr);
  1647          }

Martin