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Top Forums Shell Programming and Scripting Why stderr file descriptor redirection makes ksh's "select" construct hang. Post 302419560 by alister on Friday 7th of May 2010 01:31:33 PM
Old 05-07-2010
Quote:
Originally Posted by kchinnam
Code:
# Reset error redirection. Since select construct's output is going to STD_ERROR.
exec 2<&-

That does not reset stderr to its original location. That closes the file descriptor and it can no longer be used.

The most correct approach is to "save" the original destination of stderr in case you need it later. For example:
Code:
exec 3>&2                  # File descriptor 3 now points to the original destination of stderr
exec 2 > someotherplace    # Standard error is now redirected for all commands that follow
select ...
do
...
done 2>&3    # Select's stderr is redirected to the original stderr destination, while
             # all other commands continue to redirect stderr to "someotherplace".

Regards,
Alister

Last edited by alister; 05-07-2010 at 03:06 PM..
 

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DH-EXEC-ILLITERATE(1)						      dh-exec						     DH-EXEC-ILLITERATE(1)

NAME
dh-exec-illiterate - Write literate debhelper config files! SYNOPSIS
#! /usr/bin/dh-exec --with=illiterate,subst,install Greetings, my dear reader, and welcome to the awesome world of literate programming! Today, we're going to explore how to write a debhelper install file in a literate manner. Trust me, it's going to be lots and lots of fun! So, what exactly are we trying to accomplish? We're going to try installing a file from `src/this-file' in the source tree, to a multi-arched path in the binary file. Lets say, to `/usr/lib/foo/${DEB_HOST_MULTIARCH}/'. Of course, ${DEB_HOST_MULTIARCH} is a variable, and will be expanded later in the dh-exec pipeline. It'll be something like x86_64-linux-gnu. Furthermore, we want to install all files from the 'usr/lib' directory under debian/tmp. If we were writing an illiteral install file, we'd write this rule as: usr/lib But the above description is much easier to understand, isn't it? We're almost finished! One thing left to do, is to install a script named `rename-me', to `/usr/share/foo/new-name' - we renamed it in the process! DESCRIPTION
The dh-exec-illiterate sub-command, unlike the others, does not serve any particular case, except to serve as a warning to all, that things can be taken to an extreme, even with dh-exec. On the other hand, it is just like the other sub-commands in that it must not be called directly, but through dh-exec(1), which automatically runs all available sub-commands if run bare; or explicitly with dh-exec --with=illiterate. It is a program that will translate its input from pretty much free-form text into something that resembles an install file. At least, that's the only supported output format for now. Everything that's not recognised, will be ignored, and not printed. The recognised constructs are: `source' ... `destination' The first string between a backtick and a single quote will be treated as the source file, the next such string will be the destination. If the destination ends with a slash, dh-exec-illiterate will consider it a directory, otherwise it will output a construct that dh-exec-install can recognise as a rename operation. 'source' A string, without whitespace, between two single quotes is treated as a source, whose destination is unspecified, and is left up to dh_install(1) to figure out. ENVIRONMENT
DH_EXEC_SCRIPTDIR Indicates which directory the command-specific scripts should be sought for. If not specified, scripts will be searched for in /usr/share/dh-exec/. FILES
$DH_EXEC_SCRIPTDIR/dh-exec-illiterate-* The various scripts for the higher-level program. SEE ALSO
debhelper(1), dh-exec(1) AUTHOR
dh-exec-illiterate is copyright (C) 2011-2012 by Gergely Nagy <algernon@madhouse-project.org>. 2012-05-03 DH-EXEC-ILLITERATE(1)
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