Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Mail Systems
Eclipse Documentation

How To Guides
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Problem Solutions
Privacy Policy




Ruby Programming
Previous Page Home Next Page

Independent Children

Sometimes we don't need to be quite so hands-on: we'd like to give the subprocess its assignment and then go on about our business. Some time later, we'll check in with it to see if it has finished. For instance, we might want to kick off a long-running external sort.

exec("sort testfile > output.txt") if fork == nil
# The sort is now running in a child process
# carry on processing in the main program

# then wait for the sort to finish Process.wait

The call to Kernel::fork returns a process id in the parent, and nil in the child, so the child process will perform the Kernel::exec call and run sort. Sometime later, we issue a Process::wait call, which waits for the sort to complete (and returns its process id).

If you'd rather be notified when a child exits (instead of just waiting around), you can set up a signal handler using Kernel::trap (described on page 427). Here we set up a trap on SIGCLD, which is the signal sent on ``death of child process.''

trap("CLD") {
  pid = Process.wait
  puts "Child pid #{pid}: terminated"

exec("sort testfile > output.txt") if fork == nil

# do other stuff...

Child pid 31842: terminated
Ruby Programming
Previous Page Home Next Page

  Published under the terms of the Open Publication License Design by Interspire