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From: mkhaw@teknowledge-vaxc.UUCP
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: question - 4bsd ^Z handling and stopping a pipe
Message-ID: <13907@teknowledge-vaxc.ARPA>
Date: Sat, 20-Jun-87 23:38:47 EDT
Article-I.D.: teknowle.13907
Posted: Sat Jun 20 23:38:47 1987
Date-Received: Sun, 21-Jun-87 11:58:02 EDT
Organization: Teknowledge, Inc., Palo Alto CA
Lines: 20
Keywords: causes problems in the Elm mail program
Xref: utgpu comp.unix.questions:2542 comp.unix.wizards:2565


I've found that when I display a message in elm and ^Z at the "more" prompt,
I'm hung.  This seems to happen because elm is using a pipe to run the pager
program.  If I use "ps" from another tty to look at the hung login, I see
a parent elm process with GARBAGE in the "ps" "COMMAND" field in device-wait
state, plus a child elm, whose child is a "sh -c more", whose child is the
"more" process that I stopped.  The "sh -c" and "more" process are in stopped
state.

The only way I've found to recover is to kill the "more" and "sh -c" both.

Are there any 4bsd gurus who can explain what a SIGTSTP handler needs to do
to prevent this?  Currently Elm's SIGTSTP handler just restores default
handling (SIG_DFL) and then does a kill(0, SIGTSTP).

Mike Khaw
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