Path: utzoo!mnetor!uunet!mcvax!unido!tub!tmpmbx!csch
From: csch@tmpmbx.UUCP (Clemens Schrimpe)
Newsgroups: comp.unix.wizards
Subject: Re: Redirect Output in the Middle of a Program??
Message-ID: <819@tmpmbx.UUCP>
Date: 28 Apr 88 12:59:19 GMT
References: <13085@brl-adm.ARPA> <3571@gryphon.CTS.COM> <2841@cvl.umd.edu>
Reply-To: csch@tmpmbx.UUCP (Clemens Schrimpe)
Organization: netmbx GbR, Berlin
Lines: 31

Larry Liuqing Huang (liuqing@cvl.UUCP) writes:
{} Now more people are dialing into a system via telephone lines. It is
{} not unusual that the connection died out in the middle of a big C
{} program which you hate to start running from the beginning again.
{} 
{} Is it possible for the C program or Shell to detect the line problem?
Sure! The system will generate a SIGHUP (Hangup) signal to all processes,
which have the "hung-up" tty as their controlling tty.
[this will work ONLY, if you are using a tty, which supports modem-control
 signals (mainly DTR & DCD) and this modem-control is also enabled 
 (~CLOCAL, HUPCL and open with ~O_NDELAY)]

{} If so, is it possible to redirect all standard output and error messages
{} to a designated file from the POINT where the problem is detected and 
{} continue running?
Sure (normally :-)

Simply catch the SIGHUP, close 0, reopen it on /dev/null and
close 1 & 2 and reopen both on the file you want, then return from
the signal-routine. I havn't tried this, but it should work.

{} Any hints highly appreciated.
Ya' welcome ... ]:-}

Clemens Schrimpe

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