Visit Our UNIX and Linux User Community


Signal Processing


 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers Signal Processing
# 8  
Old 10-05-2001
Hello Perderabo,
---------------------------------------------------
"
I know that my method leaves a sleep process running if the timed command completes in time. I think that's harmless. It will be reaped by init when it exits. That's the only real cost of a very easily coded solution. Capturing and killing that last pid will drive script back up in complexity.
"
----------------------------------------------------

Does sleep process creates any kind of overhead for the unix system.

When I execute the following command (sleep 30; echo hello) &
, it create the two processes one is the shell process and the other is sleep process and the sleep process pid is always 1 greater than the shell process pid. Is it always true ?.
sanjay92
# 9  
Old 10-08-2001
Gee, thanks for the kind words guys!

No, you cannot just assume the next pid will be the current pid +1. You're on a multi-user machine. Stuff like cron runs all the time. If someone else forks first, they get the next pid. Also in a multi-cpu system, each cpu will usually reserve a chunk of 10 or so pids at once to cut down on spinlocks. Finally, pids recycle after pid 32,000.

The worst consequence of the sleep program in the background is that it is consuming a proc table entry. Too many of these and eventually you bump into maxuprc and cannot fork anymore. As long as that was not an issue, I'd just let it run. Remember that it will take code to remember or find the pid and then kill the pid. The load that this code would put on the system is trivial, but the only payback is the early death of a sleep statement...it can't make a profit.

If you really got to nail that last sleep process, a "kill $(ps -f | grep [s]leep |awk '{print $2}')" should get it.
 

Previous Thread | Next Thread
Test Your Knowledge in Computers #839
Difficulty: Medium
WebSocket is a computer communications protocol, providing half-duplex communication channels over a single TCP connection.
True or False?

7 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Continue Processing after a signal is caught

Is it possible to continue after signal is caught and control goes to function specified in the trap statement? (3 Replies)
Discussion started by: Soham
3 Replies

2. Programming

awk processing / Shell Script Processing to remove columns text file

Hello, I extracted a list of files in a directory with the command ls . However this is not my computer, so the ls functionality has been revamped so that it gives the filesizes in front like this : This is the output of ls command : I stored the output in a file filelist 1.1M... (5 Replies)
Discussion started by: ajayram
5 Replies

3. Shell Programming and Scripting

How to make parallel processing rather than serial processing ??

Hello everybody, I have a little problem with one of my program. I made a plugin for collectd (a stats collector for my servers) but I have a problem to make it run in parallel. My program gathers stats from logs, so it needs to run in background waiting for any new lines added in the log... (0 Replies)
Discussion started by: Samb95
0 Replies

4. Solaris

Signal Processing in unix

I've read the man page of singal(3) but I still can't quite understand what is the difference between SIGINT, SIGALRM and SIGTERM. Can someone tell me what is the behavioral difference among these 3 signals in kill command? Thanks! (2 Replies)
Discussion started by: joe228
2 Replies

5. Programming

alarm signal processing

I'm writing a function right now, and I want to set an alarm to avoid a timeout, here's the general idea of my code: int amt = -2; alarm(10); amt = read(fd, &t->buf, TASKBUFSIZ - tailpos); //do a read when the alarm goes off, i want to check the value of "amt" ... (1 Reply)
Discussion started by: liaobert
1 Replies

6. Programming

Signal processing

We have written a deamon which have many threads. We are registering for the SIGTERM and trying to close main thread in this signal handling. Actually these are running on Mac OS X ( BSD unix). When we are unloading the deamon with command launchctl, it's sending SIGTERM signal to our process... (1 Reply)
Discussion started by: Akshay4u
1 Replies

7. Shell Programming and Scripting

Script Signal Processing

I am trying to develop a script that will properly handle kill signals particularly kill -2. I have program (_progres) that properly receives the signal if I run it from the command line directly: _progres -T /tmp -p /home/mejones/signal.p -b 2>&1 & If I try to put it in a script (i.e.... (2 Replies)
Discussion started by: mejones99
2 Replies

Featured Tech Videos