Variable lost when redirecting output to logfile

[130272]

I want to capture the output of several commands into a logfile. In between these commands, a value is assigned to a variable.

Example code 1:
----------
#!/bin/ksh
{
command1
command2
important_command3
exit_code=${?}
command4
} |tee ${LOGFILE}
if [ ${exit_code} -ne 0 ]
then mailx -s"Failure" ${RECIPIENT} <${LOGFILE}
fi
----------

When running the script the 'if' statement fails because ${exit_code} does not exist. However, when running the following example, the variable ${exit_code} is suddenly known and the 'if' statement does not present any errors:

Example code 2:
----------
#!/bin/ksh
{
command1
command2
important_command3
exit_code=${?}
command4
}
if [ ${exit_code} -ne 0 ]
then mailx -s"Failure" ${RECIPIENT} <${LOGFILE}
fi
----------

Does anyone have an idea why the variable get lost when 'tee-ing' the output into the logfile?

 

[KenCunningham]

Have you tried exporting the value so that it persists?

 

[130272]

Yes, I have tried to export the variable but it didn't work.

 

[feherke]

Hi

Those commands executed between the braces are runned in a separate shell instance, and no variable set there can be reached by the parent process.

Feherke.

http://rootshell.be/~feherke/

 

[RodKnowlton]

Contrary to some documentation, a brace group doesn't always execute within the current environment. If you follow a brace group with | or &, it creates a subshell, just like parenthetical grouping does.

In your first case, exit_code is being defined in the subshell's environment, which the script has no access to.

One solution would be to use a flag file:

[tt]
#!/bin/ksh
{
rm /tmp/errflag > /dev/null 2>&1
command1
command2
important_command3
if [ ${?} -ne 0 ]
then
touch /tmp/errflag
fi
command4
} |tee ${LOGFILE}
if [ -e /tmp/errflag ]
then mailx -s"Failure" ${RECIPIENT} <${LOGFILE}
fi
[/tt]

Rod Knowlton

IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+