From owner-freebsd-hackers@FreeBSD.ORG  Wed Apr 27 19:57:33 2011
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Date: Wed, 27 Apr 2011 21:39:46 +0200
From: Roman Divacky <rdivacky@freebsd.org>
To: harti@freebsd.org
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Cc: hackers@freebsd.org
Subject: make question
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hi harti!


You seem to have messed with bsd make so I have a question for you  :)

When a job is about to be executed in JobStart() a pipe is created with
its ends connected to job->inPipe/job->outPipe. When the job is actually
created in JobExec() the ps.out is set to job->outPipe so that in
JobDoOutput() we can read from that pipe and basically just parse the output
for shell->noPrint and leaving it out from the output. This is meant (I think)
for supressing the "filter" thing. Ie. that if we do some @command the
restoration of setting of quiet mode is filtered out.


In -B mode we do it differently, as we invoke one shell per command we don't
have to insert quiet/verbose commands and thus avoid all the piping/parsing
dance.

So my question is - why don't we invoke one shell per command by default
and avoid the piping/parsing? Is this because of performance? I think that
the piping/parsing of the output can have worse impact than invoking a shell
for every command. Especially given that most targets consists of just one
command.

Thank you for the answer!

Roman