Very Computer

Do you know, how I can create Bourne Shell script, that kills every
child-process, that it has started as background processes. Now it is
done like this:

trap '
   killall -15 xscreensaver-command 2> /dev/null
   echo "0" > $WATCHER_FILE
   exit 0
' 1 2 3 15 20

set +o noclobber
echo "0" > $WATCHER_FILE

xscreensaver-command -watch |
while read line
do
  foo=$(echo $line | awk '{print $1}' - )
  if test "$foo" = "BLANK"
  then
    my_debug "screen is blanked"
    echo "1" > $WATCHER_FILE
  elif test "$foo" = "LOCK"
  then
    my_debug "screen is locked"
    echo "1" > $WATCHER_FILE
  elif test "$foo" = "UNBLANK"
  then
    my_debug "screen is UNblanked"
    echo "0" > $WATCHER_FILE
  fi
done

That "killall -15 xscreensaver-command" is not very elegant. I want to
kill only that one xscreensaver-command -process and child-process,
that is created in that line saying "while read line".

--

http://www.cc.jyu.fi/~juhtolv/ * * "STRAIGHT BUT NOT NARROW !!"
---------------------------------------------------------------
"if i was twice the man i could be, i'd still be half of what
you need"                                       Nine Inch Nails

   2. Useless use of awk:

      xscreensaver-command -watch | while read foo waste

   3. Useless use of test:
      do
      case $foo in
         BLANK) ...;;
         LOCK) ...;;
         UNBLANK) ...;;
         *)
      esac

   4. You are not running any background processes.  xscreensaver-command
      will not survive the script.

--
Dan Mercer

Quote:> trap '
>    killall -15 xscreensaver-command 2> /dev/null
>    echo "0" > $WATCHER_FILE
>    exit 0
> ' 1 2 3 15 20

> set +o noclobber
> echo "0" > $WATCHER_FILE

> xscreensaver-command -watch |
> while read line
> do
>   foo=$(echo $line | awk '{print $1}' - )
>   if test "$foo" = "BLANK"
>   then
>     my_debug "screen is blanked"
>     echo "1" > $WATCHER_FILE
>   elif test "$foo" = "LOCK"
>   then
>     my_debug "screen is locked"
>     echo "1" > $WATCHER_FILE
>   elif test "$foo" = "UNBLANK"
>   then
>     my_debug "screen is UNblanked"
>     echo "0" > $WATCHER_FILE
>   fi
> done

> That "killall -15 xscreensaver-command" is not very elegant. I want to
> kill only that one xscreensaver-command -process and child-process,
> that is created in that line saying "while read line".

Quote:>    2. Useless use of awk:

>       xscreensaver-command -watch | while read foo waste

>    3. Useless use of test:
>       do
>       case $foo in
>          BLANK) ...;;
>          LOCK) ...;;
>          UNBLANK) ...;;
>          *)
>       esac

Quote:>    4. You are not running any background processes.
>    xscreensaver-command will not survive the script.

Isn't that PID 3304 background process?

 * * *

Well, what if I really have many child processes as background
processes?  How can I kill them all, when my script exits? It is
possible to put PID of that process to environment variable, like
this:

$WATCHER &
WATCHER_PID="$!"

But what if I have two or more of them? Should I put those PIDs to
array?  What POSIX says about arrays?

--

http://www.cc.jyu.fi/~juhtolv/ * * "STRAIGHT BUT NOT NARROW !!"
---------------------------------------------------------------
"if i was twice the man i could be, i'd still be half of what
you need"                                       Nine Inch Nails

Quote:

>  * * *

> Well, what if I really have many child processes as background
> processes?  How can I kill them all, when my script exits? It is
> possible to put PID of that process to environment variable, like
> this:

> $WATCHER &
> WATCHER_PID="$!"

> But what if I have two or more of them? Should I put those PIDs to
> array?  What POSIX says about arrays?

   WATCHER_PIDS="${WATCHER_PIDS}${WATCHER_PIDS:+ }$!"

or you can simply "kill -term -$$" upon exiting and that will nail
every process started by the script.

--
Dan Mercer