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From: chip@vector.UUCP (Chip Rosenthal)
Newsgroups: comp.unix.xenix,comp.unix.wizards
Subject: Re: ungetty
Keywords: ungetty getty init
Message-ID: <660@vector.UUCP>
Date: 12 Dec 88 18:35:10 GMT
References: <6@rsoft.UUCP>
Reply-To: chip@vector.UUCP (Chip Rosenthal)
Organization: Dallas Semiconductor
Lines: 13

In article <6@rsoft.UUCP> frank@rsoft.UUCP (Frank I. Reiter) writes:
>Can anybody tell me how ungetty interacts with getty or point me at a good
>source of information?

As far as I know, the interface is undocumented.  But, I believe signals
SIGUSR1 and SIGUSR2 are used to communicate between /usr/lib/uucp/ungetty
and /etc/getty.  Reading between the lines, when you call ungetty with a
tty device, it looks in /etc/utmp for the PID of the getty on that line,
and then does a kill() to signal the getty to either suspend or resume.
Note that ungetty is a setuid program, which is required for the kill()
to work.
-- 
Chip Rosenthal     chip@vector.UUCP    |      Choke me in the shallow water
Dallas Semiconductor   214-450-5337    |         before I get too deep.