Mac OS X Tiger in a Nutshell

Process Management

Each command you invoke or program that you run from a Terminal window becomes a child of that terminal’s shell. The Terminal window can juggle many child processes at once, but only one at a time is brought to the foreground, writing its output (through the Unix standard output file handle) to the Terminal, and accepting keyboard input (via Unix standard input) from the user. Any other processes are either placed in the background—running but not displaying any interface or accepting input—or suspended (paused) in the process of execution.

You can control the application in the foreground by sending it Unix signals via the keystrokes listed in Table 3-1. Programs usually respond to them as listed, though individual programs may interpret them differently. (The Emacs text editor, for example, ties a text-searching function to the Control-S keystroke.)

Table 3-1. Foreground process control keystrokes

Keystroke	Description
Control-C	Sends an interrupt signal, which usually causes the program to exit.
Control-D	Sends an end-of-file signal. If a program is accepting multiple lines of input from you, this signals that you’re finished providing it.
Control-Z	Suspends the process in the foreground, and returns you to the command line.
Control-S	Suspends the process in the foreground, but keeps it in the foreground.
Control-Q	Resumes a suspended process, and brings it to the foreground.

Tip

Control-Q is a good keystroke to try if a Terminal window ceases to update ...