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Full Discussion: can't close stdin/stdout in shell
Top Forums Shell Programming and Scripting can't close stdin/stdout in shell Post 302396446 by Corona688 on Thursday 18th of February 2010 12:29:22 PM
Old 02-18-2010
Quote:
Originally Posted by mandelbrot333
ls -l /proc/self/fd >&2
You are redirecting stdout (what ls is producing) into stderr (&2).
Quite so. I have also already redirected /dev/null into stdin, and stdout into /dev/null.
Quote:
Unless you tell the script to dump stderr to /dev/null...:
Code:
./myscript 2>/dev/null

I don't want to redirect stderr, and have already redirected stdin and stdout to /dev/null. I expected ls to inherit stdin and stdout from the shell, but instead the shell for some copies stderr into stdout -- but only when I redirect ls's stdout. It doesn't just do this for terminals, either -- I've seen it do so for files, so I boiled the problem down to its minimum representation here.
Quote:
...it will be output to the shell you are running the script in.
Which is /dev/null, of course, given the prior redirections. But when I redirect it into stderr, the shell takes the extraordinary step of restoring stdout to its previous state.
Last edited by Corona688; 02-18-2010 at 01:34 PM..
 

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LEARN ABOUT SUNOS

shells

shells(4)							   File Formats 							 shells(4)

NAME

       shells - shell database

SYNOPSIS

       /etc/shells

DESCRIPTION

       The shells file contains a list of the shells on the system. Applications use this file to determine whether a shell is valid. See getuser-
       shell(3C). For each shell a single line should be present, consisting of the shell's path, relative to root.

       A hash mark (#) indicates the beginning of a comment; subsequent characters up to the end of the line are not interpreted by  the  routines
       which search the file. Blank lines are also ignored.

       The  following  default	shells are used by utilities: /bin/bash, /bin/csh, /bin/jsh, /bin/ksh, /bin/pfcsh, /bin/pfksh, /bin/pfsh, /bin/sh,
       /bin/tcsh,  /bin/zsh,  /sbin/jsh,  /sbin/sh,  /usr/bin/bash,  /usr/bin/csh,  /usr/bin/jsh,  /usr/bin/ksh,  /usr/bin/pfcsh,  /usr/bin/pfksh,
       /usr/bin/pfsh, and /usr/bin/sh, /usr/bin/tcsh, /usr/bin/zsh. Note that /etc/shells overrides the default list.

       Invalid shells in /etc/shells may cause unexpected behavior (such as being unable to log in by way of ftp(1)).

FILES

       /etc/shells	       lists shells on system

SEE ALSO

       vipw(1B), ftpd(1M), sendmail(1M), getusershell(3C), aliases(4)

SunOS 5.10							    4 Jun 2001								 shells(4)
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