#! /bin/bash

error_exit()
{
    echo "======================="
    echo $1
    echo "======================="
    cat_stack
    exit 1
}

cat_stack()
{
    P=">"
    while read LINE
    do
        printf "%s\n" "${P}${LINE}"
        P="-"${P}
    done < ${STACK}
}

add_trace()
{
    sed "s/^$1/$1: $2 - /" ${STACK} > ${SWP}
    mv ${SWP} ${STACK}
    exit 1
}

f1()
{
    push "${FUNCNAME} called from line $(caller 0 | cut -d" " -f1,2)"
    R=$(f2) || error_exit "Exception raised below call to f2() in (${FUNCNAME})"
    pop
}

f2()
{
    push "${FUNCNAME} called from line $(caller 0 | cut -d" " -f1,2)"
    echo "In f2"
    R=$(f3) || add_trace ${FUNCNAME} "Call to f3() failed"
    pop
}

f4()
{
    push "${FUNCNAME} called from line $(caller 0 | cut -d" " -f1,2)"
    echo "In f4"
    sleep 1 2>/dev/null || add_trace ${FUNCNAME} "Sleep failed"
    pop
}

f3()
{
    push "${FUNCNAME} called from line $(caller 0 | cut -d" " -f1,2)"
    echo "In f3"
    R=$(f5) || add_trace ${FUNCNAME} "Call to f5() failed"
    R=$(f4) || add_trace ${FUNCNAME} "Call to f4() failed"
    pop
}

f5()
{
    push "${FUNCNAME} called from line $(caller 0 | cut -d" " -f1,2)"
    echo "In f5"
    pop
}
push()
{
    echo $1 >> ${STACK}
    printf "%s%s\n" "$(seq -s " " ${SSO} | sed 's/[0-9]//g')" "${1}" >> ${TRACE}
    SSO=$(($SSO + 2))
}

pop()
{
    SSO=$((${SSO} - 2))
    TMP="Returned from $(tail -n 1 ${STACK} | cut -d" " -f1)"
    printf "%s%s\n" "$(seq -s " " ${SSO} | sed 's/[0-9]//g')"  "${TMP}" >> ${TRACE}
    head -n -1 ${STACK} > ${SWP}
    mv ${SWP} ${STACK}
}

STACK=stack
:>${STACK}
TRACE=trace
:>${TRACE}

SWP=/tmp/swpx
SSO=1

f1

cat trace 
f1 called from line 91 main
  f2 called from line 32 f1
    f3 called from line 40 f2
      f5 called from line 56 f3
      Returned from f5
      f4 called from line 57 f3
      Returned from f4
    Returned from f3
  Returned from f2
Returned from f1