Tracing a Qshell Variable

June 19, 2002 Timothy Prickett Morgan

Hey, Ted:

A variable is getting changed in a Qshell script, but I can’t determine where it’s happening. How can I track changes to a variable?

— Len

Add the following lines to the top of the script:

trap 'echo "DBG: $var = "$var""' DEBUG
set -x 

The trap command with the DEBUG condition executes the command between single quotes (‘) after each simple command of the script runs. In this case, Qshell echoes the value of a variable named var to the display. Replace var with the name of your variable.

The set command with -x option causes Qshell to echo each command to stderr before running it.

This is going to clutter up the display, but you should find where the variable changes and which command changes it.

— Ted

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