topic Re: exit in script! in Operating System - Linux

exit in script!

mick001 — Tue, 13 Sep 2005 08:20:50 GMT

I have a question about the exit in the script.
The idea is that the script stop when the tar command fails. so that the files are not removed. did I do it correct?

Thanks

#!/bin/bash

set -v
cd /cdr1/pmc
#
filename=/cdr1/backup.cdr.`date '+%d.%m.%Y.%k.%M.%S'`.tar
indexfile=/cdr1/backup.cdr.`date '+%d.%m.%Y.%k.%M.%S'`.txt

ls -l /cdr1/pmc >$indexfile

mkdir -p /cdr1/backup-tijd

for file in $(ls *.BF); do
mv ${file} /cdr1/backup-tijd
done

cd /cdr1/backup-tijd

tar cvf $filename .
if [ $? -ne 0 ];
then
echo "tar failed"
exit
else
rm /cdr1/backup-tijd/*
rmdir /cdr1/backup-tijd/
fi

gzip $filename
if [ $? -ne 0 ];
then
echo "gzip-failed"
exit
else
touch gzip-ok
fi
exit

Re: exit in script!

Pete Randall — Tue, 13 Sep 2005 08:29:15 GMT

Looks OK to me. You could also test it by inserting a simple command like "ll" in place of the tar.

Pete

Re: exit in script!

Piergiacomo Perini — Tue, 13 Sep 2005 08:34:42 GMT

Hi,

seems good to me !

regards
pg

Re: exit in script!

Vibhor Kumar Agarwal — Tue, 13 Sep 2005 08:36:07 GMT

You can also give you exit codes.

Like exit 3, exit 4, etc.
This will help you trace later on, as to from where has the code exited.

Re: exit in script!

James R. Ferguson — Tue, 13 Sep 2005 09:00:46 GMT

Hi:

Your handling of the return status from 'tar' and 'gzip' are fine.

I'll offer one unrelated suggestion.

The remove of the contents of the directory and then the directory itself can be coded with a recursive remove to handle both. More importantly, the use of the "*" wildcard which the shell will expand into a list of all of the files in the directory, could lead to an "argument list too long" error. [Of course, I'll grant that that was more a problem on older OS versions than newer ones where much larger argument space can be configured; but nevertheless, there is better form].

Thus, to remove your directory and its contents, simply do:

# cd /
# rm -r rm /cdr1/backup-tijd

Regards!

...JRF...

Re: exit in script!

James R. Ferguson — Tue, 13 Sep 2005 09:02:52 GMT

Hi:

Oops!!! That shoud read:

# cd /
# rm -r /cdr1/backup-tijd

Regards!

...JRF...

Re: exit in script!

A. Clay Stephenson — Tue, 13 Sep 2005 09:58:12 GMT

The most significant change I would suggest is to always save ${?} to another variable so that subsequent operations do not alter it. This becomes especially useful when printing error messages. Good practice requires that error messages generally be sent to stderr rather than stdout and that you exit with a non-zero status on failures and zero if okay.

I would make changes similar to this:

typeset -i STAT=0
gzip ${filename}
STAT=${?} # save status in another variable
if [[ ${STAT} -ne 0 ]]
then
echo "gzip-failed; status ${STAT}." >&2
exit ${STAT}
else
touch gzip-ok
fi
exit ${STAT}

Re: exit in script!

Vibhor Kumar Agarwal — Wed, 14 Sep 2005 05:45:41 GMT

Regarding deleting recursively, just a small enhancement:

rm -rf /directory

This will help if the file is read only.

Re: exit in script!

Muthukumar_5 — Wed, 14 Sep 2005 05:53:16 GMT

Use this script.

#!/bin/bash
# Exit Status
# 0 - Success; 1 - Tar failed;2 - gunzip failed
set -x
cd /cdr1/pmc

filename=/cdr1/backup.cdr.`date '+%d.%m.%Y.%k.%M.%S'`.tar
indexfile=/cdr1/backup.cdr.`date '+%d.%m.%Y.%k.%M.%S'`.txt

ls -l /cdr1/pmc >$indexfile

mkdir -p /cdr1/backup-tijd

for file in $(ls *.BF); do
mv -f ${file} /cdr1/backup-tijd
done

cd /cdr1/backup-tijd

tar cvf $filename .
if [ $? -ne 0 ];
then
echo "tar failed"
exit 1
else
rm -rf /cdr1/backup-tijd/
fi

gzip $filename
if [ $? -ne 0 ];
then
echo "gzip-failed"
exit 2
else
echo "gunzip-ok"
fi

exit 0
set +x

hth.

Re: exit in script!

mick001 — Wed, 14 Sep 2005 08:30:50 GMT

Hi

Why do you use set -x ?

Thanks

Re: exit in script!

Orhan Biyiklioglu — Wed, 14 Sep 2005 08:36:54 GMT

set -x is used to enable shell tracing mode. In shell tracing mode each command is printed in the exact form that it is executed.

This can be used to debug shell scripts.

Re: exit in script!

James R. Ferguson — Wed, 14 Sep 2005 08:45:00 GMT

Hi:

'set -x' causes a script's commands and their arguments to be printed as they are executed. This is useful to find what and where a script is doing; a useful debuging tool.

Another one is '-n'. This means syntax-check but don't actually execute.

Consult the manpages for 'sh-posix' for a full list of the other very useful shell options.

You can always do this:

# sh -x yourscript

That is, you do NOT need to actually modify a script to temporarily leverage a set option.

Regards!

...JRF...