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_handles="$@"
  30
  31     local handle
  32     for handle in $trap_handles; do
  33         local var="exit_trap_handle_$handle"
  34         local trap_num=${!var}
  35         exit_actions[$trap_num]=""
  36         eval unset $var
  37     done
  38 }
  39
  40 print_exit_traps() {
  41
  42     local i num_items=${#exit_actions[@]}
  43     for i in $(seq 0 $((num_items-1))); do
  44         if [ -z "${exit_actions[$i]}" ]; then
  45             continue
  46         fi
  47         echo "${exit_actions[$i]}"
  48     done
  49
  50 }
  51
  52 run_exit_traps() {
  53
  54     local i num_items=${#exit_actions[@]}
  55     for i in $(seq $((num_items-1)) -1 0); do
  56         if [ -z "${exit_actions[$i]}" ]; then
  57             continue
  58         fi
  59         eval ${exit_actions[$i]}
  60     done
  61
  62 }
  63
  64 trap run_exit_traps EXIT
  65
  66 if [ "$1" = "unit_test" ]; then
  67     if ! push_exit_trap "echo \"this is the first trap\"" "a"; then
  68         echo "failed to install trap 1"
  69         exit 1
  70     fi
  71     if ! push_exit_trap "echo \"this is the second trap\"" "b"; then
  72         echo "failed to install trap 2"
  73         exit 2
  74     fi
  75     delete_exit_trap "b"
  76     if ! push_exit_trap "echo \"this is the third trap\"" "b"; then
  77         echo "failed to install trap 3"
  78         exit 3
  79     fi
  80
  81     # to see the traps
  82     print_exit_traps
  83     echo "------------"
  84
  85     delete_exit_trap "a" "b"
  86     print_exit_traps
  87     echo "------------"
  88
  89     if ! push_exit_trap "echo \"this is the first trap\"" "a"; then
  90         echo "failed to install trap 1"
  91         exit 1
  92     fi
  93     if ! push_exit_trap "echo \"this is the second trap\"" "b"; then
  94         echo "failed to install trap 2"
  95         exit 2
  96     fi
  97     if ! push_exit_trap "echo \"this is the third trap\"" "c"; then
  98         echo "failed to install trap 3"
  99         exit 3
 100     fi
 101     delete_exit_trap "a" "c"
 102
 103     print_exit_traps
 104     echo "------------"
 105 fi