It can make for some pretty excellent stack traces from complicated (even multi-file) bash-based programs; e.g.,

$ ./track.sh 
I failed!
  at make_failure (file "common.sh" line 3)
  at d (file "./track.sh" line 43)
  at c (file "./track.sh" line 38)
  at b (file "./track.sh" line 33)
  at a (file "./track.sh" line 28)
  at main (file "./track.sh" line 54)

From the source files:

$ nl -ba < common.sh
     1	function make_failure {
     2	    echo "I failed!"
     3	    false
     4	}

$ nl -ba < track.sh
     1	#!/bin/bash
     2	
     3	. "common.sh"
     4	
     5	function stack_trace
     6	{
     7	    set +o xtrace
     8	    set +o errexit
     9	    set +o errtrace
    10	    trap '' ERR
    11	
    12	    for (( i = 0; i < ${#FUNCNAME[@]}; i++ )); do
    13	        if [[ "${FUNCNAME[i]}" == stack_trace ]]; then
    14	            continue
    15	        fi
    16	        if (( i > 0 )); then
    17	            line="${BASH_LINENO[$((i - 1))]}"
    18	        else
    19	            line="${LINENO}"
    20	        fi
    21	        printf '  at %s (file "%s" line %d)\n' "${FUNCNAME[i]}" \
    22	            "${BASH_SOURCE[i]}" "${line}"
    23	    done
    24	}
    25	
    26	function a
    27	{
    28	    b
    29	}
    30	
    31	function b
    32	{
    33	    c
    34	}
    35	
    36	function c
    37	{
    38	    d
    39	}
    40	
    41	function d
    42	{
    43	    make_failure
    44	}
    45	
    46	#
    47	# Install our error handling trap, so that we can have stack traces on
    48	# failures.  We set "errtrace" so that the ERR trap handler is inherited
    49	# by each function call.
    50	#
    51	trap stack_trace ERR
    52	set -o errtrace
    53	
    54	a