Bash-4.2 distribution sources and documentation

examples/scripts/timeout3

@@ -1,56 +1,57 @@
 #!/bin/bash
 #
-# The Bash shell script executes a command with a time-out.
-# Upon time-out expiration SIGTERM (15) is sent to the process. If the signal
-# is blocked, then the subsequent SIGKILL (9) terminates it.
-#
+# The Bash script executes a command with a time-out.
 # Based on the Bash documentation example.
-
-# Hello Chet,
-# please find attached a "little easier"  :-)  to comprehend
-# time-out example.  If you find it suitable, feel free to include
-# anywhere: the very same logic as in the original examples/scripts, a
-# little more transparent implementation to my taste.
 #
-# Dmitry V Golovashkin <Dmitry.Golovashkin@sas.com>
+# Upon time-out expiration SIGTERM (15) is sent to the process.  If the signal
+# is blocked, then the subsequent SIGKILL (9) terminates it.
+# Dmitry V Golovashkin (E-mail: dvg@ieee.org)
+#
+script_name="${0##*/}"
 
-scriptName="${0##*/}"
+# Default values.
+readonly param_timeout=5
+readonly param_interval=1
+readonly param_delay=1
 
-declare -i DEFAULT_TIMEOUT=9
-declare -i DEFAULT_INTERVAL=1
-declare -i DEFAULT_DELAY=1
+declare -i timeout=param_timeout
+declare -i interval=param_interval
+declare -i delay=param_delay
 
-# Timeout.
-declare -i timeout=DEFAULT_TIMEOUT
-# Interval between checks if the process is still alive.
-declare -i interval=DEFAULT_INTERVAL
-# Delay between posting the SIGTERM signal and destroying the process by SIGKILL.
-declare -i delay=DEFAULT_DELAY
+blue="$(tput setaf 4)"
+bold_red="$(tput bold; tput setaf 1)"
+off="$(tput sgr0)"
 
-function printUsage() {
-    cat <<EOF
+function print_usage() {
+cat <<EOF
 
-Synopsis
-    $scriptName [-t timeout] [-i interval] [-d delay] command
-    Execute a command with a time-out.
-    Upon time-out expiration SIGTERM (15) is sent to the process. If SIGTERM
-    signal is blocked, then the subsequent SIGKILL (9) terminates it.
+Synopsis:  $script_name [-t timeout] [-i interval] [-d delay] command
 
-    -t timeout
-        Number of seconds to wait for command completion.
-        Default value: $DEFAULT_TIMEOUT seconds.
+Executes the command with a time-out.  Upon time-out expiration SIGTERM (15) is
+sent to the process.  If SIGTERM signal is blocked, then the subsequent SIGKILL
+(9) terminates it.
 
-    -i interval
-        Interval between checks if the process is still alive.
-        Positive integer, default value: $DEFAULT_INTERVAL seconds.
+$blue-t timeout$off
+    Number of seconds to wait for command completion.
+    Default value: $param_timeout seconds.  In some practical situations
+    this value ${bold_red}must$off be increased (for instance -t 180) to allow
+    the command to complete.
 
-    -d delay
-        Delay between posting the SIGTERM signal and destroying the
-        process by SIGKILL. Default value: $DEFAULT_DELAY seconds.
+$blue-i interval$off
+    Interval between checks if the process is still alive.
+    Positive integer, default value: $param_interval seconds.
+    Default value is OK for most situations.
+
+$blue-d delay$off
+    Delay between posting the SIGTERM signal and destroying the process by
+    SIGKILL.  Default value: $param_delay seconds.
+    Default value is OK for most situations.
 
 As of today, Bash does not support floating point arithmetic (sleep does),
-therefore all delay/time values must be integers.
+therefore all time values must be integers.
+Dmitry Golovashkin (E-mail: dvg@ieee.org)
 EOF
+exit 1 # No useful work was done.
 }
 
 # Options.
@@ -59,7 +60,7 @@ while getopts ":t:i:d:" option; do
         t) timeout=$OPTARG ;;
         i) interval=$OPTARG ;;
         d) delay=$OPTARG ;;
-        *) printUsage; exit 1 ;;
+        *) print_usage ;;
     esac
 done
 shift $((OPTIND - 1))
@@ -67,11 +68,10 @@ shift $((OPTIND - 1))
 # $# should be at least 1 (the command to execute), however it may be strictly
 # greater than 1 if the command itself has options.
 if (($# == 0 || interval <= 0)); then
-    printUsage
-    exit 1
+    print_usage
 fi
 
-# kill -0 pid   Exit code indicates if a signal may be sent to $pid process.
+# kill -0 pid   Exit code indicates if a signal may be sent to "pid" process.
 (
     ((t = timeout))
 
@@ -89,3 +89,4 @@ fi
 ) 2> /dev/null &
 
 exec "$@"
+