hphp/tools/timeout.sh

   1 #!/bin/bash
   2 #
   3 # The Bash shell script executes a command with a time-out.
   4 # Upon time-out expiration SIGTERM (15) is sent to the process. If the signal
   5 # is blocked, then the subsequent SIGKILL (9) terminates it.
   6 #
   7 # Based on the Bash documentation example.
   8
   9 # Hello Chet,
  10 # please find attached a "little easier"  :-)  to comprehend
  11 # time-out example.  If you find it suitable, feel free to include
  12 # anywhere: the very same logic as in the original examples/scripts, a
  13 # little more transparent implementation to my taste.
  14 #
  15 # Dmitry V Golovashkin <Dmitry.Golovashkin@sas.com>
  16
  17 scriptName="${0##*/}"
  18
  19 declare -i DEFAULT_TIMEOUT=9
  20 declare -i DEFAULT_INTERVAL=1
  21 declare -i DEFAULT_DELAY=1
  22
  23 # Timeout.
  24 declare -i timeout=DEFAULT_TIMEOUT
  25 # Interval between checks if the process is still alive.
  26 declare -i interval=DEFAULT_INTERVAL
  27 # Delay between posting the SIGTERM signal and destroying the process by SIGKILL.
  28 declare -i delay=DEFAULT_DELAY
  29
  30 function printUsage() {
  31     cat <<EOF
  32
  33 Synopsis
  34     $scriptName [-t timeout] [-i interval] [-d delay] command
  35     Execute a command with a time-out.
  36     Upon time-out expiration SIGTERM (15) is sent to the process. If SIGTERM
  37     signal is blocked, then the subsequent SIGKILL (9) terminates it.
  38
  39     -t timeout
  40         Number of seconds to wait for command completion.
  41         Default value: $DEFAULT_TIMEOUT seconds.
  42
  43     -i interval
  44         Interval between checks if the process is still alive.
  45         Positive integer, default value: $DEFAULT_INTERVAL seconds.
  46
  47     -d delay
  48         Delay between posting the SIGTERM signal and destroying the
  49         process by SIGKILL. Default value: $DEFAULT_DELAY seconds.
  50
  51 As of today, Bash does not support floating point arithmetic (sleep does),
  52 therefore all delay/time values must be integers.
  53 EOF
  54 }
  55
  56 # Options.
  57 while getopts ":t:i:d:" option; do
  58     case "$option" in
  59         t) timeout=$OPTARG ;;
  60         i) interval=$OPTARG ;;
  61         d) delay=$OPTARG ;;
  62         *) printUsage; exit 1 ;;
  63     esac
  64 done
  65 shift $((OPTIND - 1))
  66
  67 # $# should be at least 1 (the command to execute), however it may be strictly
  68 # greater than 1 if the command itself has options.
  69 if (($# == 0 || interval <= 0)); then
  70     printUsage
  71     exit 1
  72 fi
  73
  74 # kill -0 pid   Exit code indicates if a signal may be sent to $pid process.
  75 (
  76     ((t = timeout))
  77
  78     while ((t > 0)); do
  79         sleep $interval
  80         kill -0 $$ || exit 0
  81         ((t -= interval))
  82     done
  83
  84     # Be nice, post SIGTERM first.
  85     # The 'exit 0' below will be executed if any preceeding command fails.
  86     kill -s SIGTERM $$ && kill -0 $$ || exit 0
  87     sleep $delay
  88     kill -s SIGKILL $$
  89 ) 2> /dev/null &
  90
  91 exec "$@"