How to display last command that failed when using bash set -e?

Question

I am using set -e to stop execution of a script on first error.

The problem is that this does not tell me what went wrong.

How can update a bash scr

Answer 1

Instead of set -e, use an ERR trap; you can pass $BASH_LINENO in to get the specific line number on which the error occurred. I provide a script taking advantage of this in my answer at https://stackoverflow.com/a/185900/14122

To summarize:

error() {
   local sourcefile=$1
   local lineno=$2
   # ...logic for reporting an error at line $lineno
   #    of file $sourcefile goes here...
}
trap 'error "${BASH_SOURCE}" "${LINENO}"' ERR

Answer 2

1. make err.sh

   set -e
   trap 'echo "ERROR: $BASH_SOURCE:$LINENO $BASH_COMMAND" >&2' ERR
   

2. include it (. err.sh) in all your scripts.

3. replace any

   ... | while read X ; do ... ; done

   with

   while read X ; do ... ; done < <( ... )

   in your scripts for the trap to give the correct line number/command in the error message

Answer 3

You can't use set -e by itself because processing will immediately stop after any error. Take a look at the Set Builtin section of the Bash Reference Manual for more information about the -x and -v options, which you can use for debugging.

Something like:

set -e
set -v

will exit on any error, while showing you each input line as it is read. It will not, however, show you just the line with the error. For that, you will need to do your own explicit error checking.

For example:

set +e
if false; then
    real_exit_status=$?
    echo 'Some useful error message.' >&2
    exit $real_exit_status
fi

Answer 4

set -ex will show (all) lines as they are executed and stop at the first command returning nonzero (not as part of if/while/until constructs).

Answer 5

Have you tried with --verbose?

bash --verbose script.sh