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Full Discussion: Signals in Shell
Top Forums UNIX for Advanced & Expert Users Signals in Shell Post 35046 by Perderabo on Wednesday 26th of March 2003 09:39:01 AM
Old 03-26-2003
You should be able to get that to work. Do you need the parent to respond immediately? If not, I would not use signals. I would have the child write a status file and once every 10 minutes the parent would see if the status file exists. If so, it would read it, delete it, and take appropriate action. This is a much wider channel of communication between the processes and it bypasses the problems that signals can cause in scripts.

When the parent launches the child, it should save the pid:
child &
pid=$!

Then to see if the child is still running, use the kill command with signal zero:

if kill -0 $pid ; then
echo child is still running
else
echo child is dead
fi
 

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LEARN ABOUT NETBSD

wait

WAIT(1) 						    BSD General Commands Manual 						   WAIT(1)

NAME

     wait -- await process completion

SYNOPSIS

     wait [pid]

DESCRIPTION

     If invoked with no arguments, the wait utility waits until all existing child processes in the background have terminated.

     Available operands:

     pid     If a pid operand is specified, and it is the process ID of a background child process that still exists, the wait utility waits until
	     that process has completed and consumes its status information, without consuming the status information of any other process.

	     If a pid operand is specified that is not the process ID of a child background process that still exists, wait exits without waiting
	     for any processes to complete.

     The wait utility exits with one of the following values:

     0	     The wait utility was invoked with no operands and all of the existing background child processes have terminated, or the process
	     specified by the pid operand exited normally with 0 as its exit status.

     >0      The specified process did not exist and its exit status information was not available, or the specified process existed or its exit
	     status information was available, and it terminated with a non-zero exit status.

     If the specified process terminated abnormally due to the receipt of a signal, the exit status information of wait contains that termination
     status as well.

STANDARDS

     The wait command is expected to be IEEE Std 1003.2 (``POSIX.2'') compatible.

BSD
								   June 5, 1993 							       BSD
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