Kazy

If I have a program, and someone closes it, how can I execute one last command before it actually closes? For instance, I have two programs that communicate with each other. if the user closes one of the programs, I need to send a msg to the other program before it closes, telling the other program to close as well. Is there an easy way to do this?

Polyphemus_

Differs per OS, i believe. For what OS is the program? Is it graphical / consolebased?

Kazy

linux/unix and is console based

Infinite Recursion

ps -ef | grep nameOfProg

pipe that into an awk script, pull out the PID and do a kill -9 on it prior to the close of the other program.

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L7Sqr

Do a man on atexit
Supposing the first application is not being abnormally terminated, simply register you function(s) and be on your way.

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Cerulean

Well you catch the SIGTERM signal that is sent to application 1 to tell it to shut down, and then you can do whatever clean up work you'd like to do e.g send a signal like SIGUSR1 to application 2 which will inform it that application 1 has closed down.
This won't work if you send SIGKILL to application 1, mind - there is no way to catch a SIGKILL signal, so it will die on you in a puff of smoke and have no time to notify app 2.

Edit:
Another why might be to use a heartbeat UDP packet - application 1 sends a packet to application 2 over a UDP socket every 5 seconds. If application 2 doesn't receive a packet after, say, 15 seconds, then you know that application 1 has died.

Kazy

ok so I put the section of code that uses the pipe into a try block.. then I can use a catch block to look for the SIGTERM signal then exit? Will the system throw the exception to the catch block or do I have to somehow check for SIGTERM then throw the exception myself?

L7Sqr

You need to provide the way they are communicating.
If by threads, your SIG* won't be as easy to implement as you might think. If by sockets, there are other means to terminate (you should be monitoring your fds).
More information will lead to more specific answers.

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Kazy

I'm using a named pipe created with mkfifo, does that help?

Dizzutch

you gotta catch the kill signal, and do something instead. whether the kill signal comes from the user hitting ctrl-c or it getting a kill from the OS.

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