build/exit_traps.sh

   1 #!/bin/bash
   2
   3 # a framework for stacking EXIT traps
   4 # this could, should be further enhanced to allow stacks of traps for various
   5 # exits.  but right now it's hard-coded for EXIT traps
   6
   7 exit_actions=()
   8
   9 push_exit_trap() {
  10     local action="$1"
  11     local trap_handle="$2"
  12
  13     local var="exit_trap_handle_$trap_handle"
  14
  15     if [ -n "${!var}" ]; then
  16         echo "fail!  trap handle $trap_handle is already in use"
  17         return 1
  18     fi
  19
  20     local num_items=${#exit_actions[@]}
  21     exit_actions[$num_items]="$action"
  22     eval $var="$num_items"
  23
  24     return 0
  25
  26 }
  27
  28 delete_exit_trap() {
  29     local trap_handle="$1"
  30
  31     local var="exit_trap_handle_$trap_handle"
  32     local trap_num=${!var}
  33     exit_actions[$trap_num]=""
  34     eval unset $var
  35 }
  36
  37 print_exit_traps() {
  38
  39     local i num_items=${#exit_actions[@]}
  40     for i in $(seq 0 $((num_items-1))); do
  41         if [ -z "${exit_actions[$i]}" ]; then
  42             continue
  43         fi
  44         echo "${exit_actions[$i]}"
  45     done
  46
  47 }
  48
  49 run_exit_traps() {
  50
  51     local i num_items=${#exit_actions[@]}
  52     for i in $(seq $((num_items-1)) -1 0); do
  53         if [ -z "${exit_actions[$i]}" ]; then
  54             continue
  55         fi
  56         eval ${exit_actions[$i]}
  57     done
  58
  59 }
  60
  61 trap run_exit_traps EXIT
  62
  63 #if ! push_exit_trap "echo \"this is the first trap\"" "a"; then
  64 #    echo "failed to install trap 1"
  65 #    exit 1
  66 #fi
  67 #if ! push_exit_trap "echo \"this is the second trap\"" "b"; then
  68 #    echo "failed to install trap 2"
  69 #    exit 2
  70 #fi
  71 #delete_exit_trap "b"
  72 #if ! push_exit_trap "echo \"this is the third trap\"" "b"; then
  73 #    echo "failed to install trap 3"
  74 #    exit 3
  75 #fi
  76
  77 # to see the traps
  78 #print_exit_traps