kern/154915: [libc] [patch] Force stdio output streams to line-buffered mode

Jeremie Le Hen jeremie at
Thu Apr 5 07:00:15 UTC 2012

The following reply was made to PR kern/154915; it has been noted by GNATS.

From: Jeremie Le Hen <jeremie at>
To: Oliver Fromme <olli at>
Cc: bug-followup at, jeremie at
Subject: Re: kern/154915: [libc] [patch] Force stdio output streams to
 line-buffered mode
Date: Thu, 5 Apr 2012 08:55:00 +0200

 Hi Oliver,
 I'm top-posting to let you handle this mail quickly.
 Can you please close this PR.  The content is messy, the subject is
 misleading and I don't think these points will help the patch to be
 committed.  I will open a new PR with the new patch that doesn't modify
 On Thu, Feb 16, 2012 at 02:49:50PM +0100, Oliver Fromme wrote:
 > I think introducing an environment variable for this purpose
 > is a bad hack.  I would advise against this.
 > Many tools already have options for unbuffered or line-buffered
 > output (for example cat -u), and there are also other ways to
 > circumvent such problems.
 > For example, the problem quoted in the PR can be solved like this,
 > using the -u option of cat:
 >     $ iostat -x 1 | cat -un | grep ad1
 > or avoiding cat completely (also might be more efficient,
 > saving one process and one pipe, though I haven't benchmarked
 > this):
 >     $ iostat -x 1 | awk '{n+=1} /ad1/{print n, $0}'
 > For certain other cases, I have the following alias in my ~/.zshrc
 > that simulates a TTY environment for a tool so it is forced to
 > use line-buffered output:
 >     alias intty='script -qt0 /dev/null'
 > So I can write:
 >     $ intty sometool -args | grep ...
 > However, the intty alias only works when it is the first command
 > in a pipeline (this is a limitation of the "script" command).
 > In the above example, the cat command is not the first, but a
 > subshell can be used to work around this:
 >     $ intty sh -c 'iostat -x 1 | cat -n' | grep ad1
 > (It should work with any shell that supports aliases, not just
 > zsh, of course.)
 > I suggest closing this PR.
 > Best regards
 > Oliver
 Jeremie Le Hen
 Men are born free and equal.  Later on, they're on their own.
 				Jean Yanne

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