Get function backtrace in bash from trap handler (using caller)

Question

I know that you can use 'caller' to get a backtrace of function calls in bash:

#! /bin/bash
Backtrace () {
   echo "Backtrace is:"
   i=0
   while caller $i
   do
      i=$((i+1))
   done
}
myFunc () {
   Backtrace
}
myFunc

Prints:

Backtrace is:
11 myFunc ./test.sh
13 main ./test.sh

My question is, lets say I have a script which uses 'set -e' to terminate on any unchecked failure. Is it possible to get a line number of where the script failed (and its callers)

I've tried naively doing: trap 'Backtrace' EXIT, but that gives me '1 main./test.sh' rather than the line number of the failing command

Answer 1

I'm not sure if it will work, but try adding ERR to your list of trap 'd signals. Maybe your code will be invoked before the set -e stuff takes over, in which case you'll be back in business.

Answer 2

if the trap is a result of a non-zero return-code, you can figure this out by trapping SIGCHLD and checking if $? -eq 0 $? -eq 0

The downside to this is that the trap will fire any time a child process returns. But you can just short-circuit with the [[ $? -eq 0 ]] return [[ $? -eq 0 ]] return

See trap fails to catch SIGSEGV for more detail.

Sorry if I misunderstood your question, hopefully this is helpful. I know your question is not specific to SIGSEGV, but it applies to any time set -e causes an exit due to a non-zero status code, so should still be applicable

EDIT: To save you the suspense, to trap SIGCHLD, you use trap <expression> CHLD , not trap <expression> SIGCHLD as most reasonable people assume:)