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Full Discussion: How to trap set -o nounset in bash
Top Forums Shell Programming and Scripting How to trap set -o nounset in bash Post 302534483 by jelloir on Tuesday 28th of June 2011 03:57:44 AM
Old 06-28-2011
How to trap set -o nounset in bash
I have a bash script using "set -o nounset" to prevent unset variables.

However I have created a trap to run some cleanup options upon exit of the script which works fine for CTRL-C, etc. but if it hits and unset variable the trap does not run and the script bails out without having tidied up after itself.

I have been trying various signals but none seem to cause the trap to execute when hitting and unset variable.

What signal does "set -o nounset" use?

Below is an example (I have tried various other signals)

Code:
#!/bin/bash

set -u

trap "echo trap_has_run > /tmp/foo.txt" 1 2 3 15 ERR

echo $unsetvar

Code:
> /tmp/traptest.sh
/tmp/traptest.sh: line 7: unsetvar: unbound variable
> cat  /tmp/foo.txt
cat: /tmp/foo.txt: No such file or directory

 

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LEARN ABOUT CENTOS

bashbug

BASHBUG(1)						      General Commands Manual							BASHBUG(1)

NAME

       bashbug - report a bug in bash

SYNOPSIS

       bashbug [--version] [--help] [email-address]

DESCRIPTION

       bashbug	is  a shell script to help the user compose and mail bug reports concerning bash in a standard format.	bashbug invokes the editor
       specified by the environment variable EDITOR on a temporary copy of the bug report format outline. The user must fill  in  the  appropriate
       fields  and  exit  the  editor.	 bashbug  then	mails the completed report to bug-bash@gnu.org, or email-address.  If the report cannot be
       mailed, it is saved in the file dead.bashbug in the invoking user's home directory.

       The bug report format outline consists of several sections.  The first section provides information about the  machine,	operating  system,
       the  bash  version, and the compilation environment.  The second section should be filled in with a description of the bug.  The third sec-
       tion should be a description of how to reproduce the bug.  The optional fourth section is for a proposed fix.  Fixes are encouraged.

ENVIRONMENT

       bashbug will utilize the following environment variables if they exist:

       EDITOR Specifies the preferred editor. If EDITOR is not set, bashbug defaults to emacs.

       HOME   Directory in which the failed bug report is saved if the mail fails.

       TMPDIR Directory in which to create temporary files and directories.

SEE ALSO

       bash(1)

AUTHORS

       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet@po.cwru.edu

GNU Bash-4.0							   1998 July 30 							BASHBUG(1)
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