Question

I want to trap the error inside the shell script, and then generate some report for the reason for the error:

trap 'error_handler' ERR

In my error_handler function, I want to give the reason for why the ERR signal was caught (e.g. “permission denied”, “cannot find remote host”, etc.).

Is this possible?

Answer 1

Not really. The only piece of information you are guaranteed to have available in your error handler is the exit status of the process that triggered the ERR, in $?. You don’t even know the name of the process or its process ID. I think the error handler is meant for general purpose clean-up before exiting a script, so it doesn’t matter which process had the non-zero exit status or why.

You are better off reporting on or dealing with errors immediately when they happen, like so:

rm foo || { echo "File removal failed"; }

Note that most commands will print their own failure notices to standard error.