bug#44941: 28.0.50; M-x grep, perhaps all asynch subprocesses

[Jean Louis]

* Eli Zaretskii <eliz@gnu.org> [2020-11-30 19:39]:
> > From: Andreas Schwab <schwab@linux-m68k.org>
> > Cc: rms@gnu.org,  44941@debbugs.gnu.org
> > Date: Mon, 30 Nov 2020 16:47:28 +0100
> > 
> > On Nov 30 2020, Eli Zaretskii wrote:
> > 
> > >> From: Richard Stallman <rms@gnu.org>
> > >> Cc: 44941@debbugs.gnu.org
> > >> Date: Sun, 29 Nov 2020 23:46:22 -0500
> > >> 
> > >> Here is the cgrep script:
> > >> 
> > >> #!/bin/bash
> > >> 
> > >> grep -a "$@" | cut -c -200
> > >> 
> > >> cut seems to be responsible for the problem by buffering output even to 
> > >> a tty.
> > >
> > > Sounds like a useful feature to ask Grep developers to add it.
> > 
> > That feature already exists: stdbuf.
> 
> I'm not sure I understand: I meant the feature to limit the output
> lines to a given column count.

Is it not this option for limiting?

        -m NUM, --max-count=NUM
                Stop reading a  file after NUM matching  lines.  If the
                input is  standard input from  a regular file,  and NUM
                matching  lines  are  output,  grep  ensures  that  the
                standard  input is  positioned to  just after  the last
                matching  line   before  exiting,  regardless   of  the
                presence  of trailing  context lines.   This enables  a
                calling process  to resume  a search.  When  grep stops
                after  NUM  matching  lines, it  outputs  any  trailing
                context lines.  When  the -c or --count  option is also
                used, grep  does not output  a count greater  than NUM.
                When the -v or --invert-match option is also used, grep
                stops after outputting NUM non-matching lines.