What's different between Ctrl+Z and Ctrl+C in Unix command line?

Solution 1:

Control+Z is used for suspending a process by sending it the signal SIGSTOP, which cannot be intercepted by the program. While Control+C is used to kill a process with the signal SIGINT, and can be intercepted by a program so it can clean its self up before exiting, or not exit at all.

If you suspend a process, this will show up in the shell to tell you it has been suspended:

[1]+  Stopped                 yes

However, if you kill one, you won't see any confirmation other than being dropped back to a shell prompt. When you suspend a process, you can do fancy things with it, too. For instance, running this:

fg

With a program suspended will bring it back to the foreground.

And running the command

bg

With a program suspended will allow it to run in the background (the program's output will still go to the TTY, though).

If you want to kill a suspended program, you don't have to bring it back with fg first, you can simply do the command:

kill %1

If you have multiple suspended commands, running

jobs

will list them, like this:

[1]-  Stopped                 pianobar
[2]+  Stopped                 yes

Using %#, where # is the job number (the one in square brackets from the jobs output) with bg, fg, or kill, can be used to do the action on that job.

Solution 2:

• http://en.wikipedia.org/wiki/SIGSTOP
• http://en.wikipedia.org/wiki/SIGTSTP
• http://en.wikipedia.org/wiki/SIGINT_(POSIX)

Ctrl+Z suspends the process with SIGTSTP, you can resume it later. Ctrl+C kills the process with SIGINT, which terminates the process unless it is handled/ignored by the target, so you can't resume it. There's also a SIGSTOP which can be sent by kill() and which the process can't intercept. SIGCONT is the counterpart to both SIGSTOP and SIGTSTP that un-suspends the process.