34.6. The SIGHUP Signal

When a controlling process loses its terminal connection, the kernel sends it a SIGHUP signal to inform it of this fact. (A SIGCONT signal is also sent, to ensure that the process is restarted in case it had been previously stopped by a signal.) Typically, this may occur in two circumstances:

• When a “disconnect” is detected by the terminal driver, indicating a loss of signal on a modem or terminal line.

• When a terminal window is closed on a workstation. This occurs because the last open file descriptor for the master side of the pseudoterminal associated with the terminal window is closed.