From: Stephane Chazelas <stephane.chazelas@gmail.com>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: Nathan Dorfman <na@rtfm.net>, zsh-users@zsh.org
Subject: Re: Redirect a specific file descriptor to a pipe?
Date: Fri, 10 Mar 2017 17:22:19 +0000 [thread overview]
Message-ID: <20170310172219.GA4206@chaz.gmail.com> (raw)
In-Reply-To: <170309180417.ZM14034__34042.4779606566$1489111700$gmane$org@torch.brasslantern.com>
2017-03-09 18:04:17 -0800, Bart Schaefer:
> On Mar 9, 5:21pm, Nathan Dorfman wrote:
> }
> } strace -o /dev/fd/3 ./a.out > out.log 2> err.log 3>XXX
> }
> } Instead of file XXX, I'd like to send fd 3 to |less. Is it possible?
>
> You just need this:
>
> strace -o /dev/fd/3 ./a.out > out.log 2> err.log 3>&1 | less
[...]
No quite. There are two issues here, one zsh specific:
cmd > file | cmd2
In zsh (with multios on by default) is special and redirects
stdout both to file and cmd2 (and the 3>&1 would also redirect
fd 3 to both).
In Bourne-like syntax, you'd also need to change the order:
strace -o /dev/fd/3 ./a.out 3>&1 > out.log 2> err.log | less
That is, redirect the fd 3 to the same thing as fd 1 at the time
that fd 1 was the pipe, *and then* redirect fd 1 to out.log.
In zsh, to avoid the multios effect, you can do:
{strace -o /dev/fd/3 ./a.out 3>&1 > out.log 2> err.log} | less
or disable multios (set +o multios).
--
Stephane
next prev parent reply other threads:[~2017-03-10 17:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-10 0:21 Nathan Dorfman
2017-03-10 2:04 ` Bart Schaefer
[not found] ` <170309180417.ZM14034__34042.4779606566$1489111700$gmane$org@torch.brasslantern.com>
2017-03-10 17:22 ` Stephane Chazelas [this message]
2017-03-10 18:51 ` Bart Schaefer
2017-03-10 23:32 ` Nathan Dorfman
2017-03-11 0:17 ` Mikael Magnusson
2017-03-11 2:24 ` Bart Schaefer
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