I'm trying to write a mail program which might contain data that a user wouldn't want to lose upon a broken SSH/telnet connection. Would SIGHUP be sent to the process? After all, it's the "hangup" signal...


By default the process will be sent a SIGHUP. The default signal handler (trap) will shutdown the program relatively gracefully, but won't save the users work.

In your case, I would have the program include a trap routine that saves the user's work when a SIGHUP is received. You can catch and handle all signals except SIGKILL. You may also want to run the same routine for a SIGTERM interupt.

There are other mechanisms that can be used to avoid getting a SIGHUP signal, but handling the signal is the simplest and safest. If the other approachs fail, or a SIGHUP is sent with the kill command your process would still shutdown without saving the work.

  • With ssh host 'cmd', cmd won't get a SIGHUP if the connection drops. cmd could get a SIGPIPE if it tries to write something on stdout/stderr after the connection has dropped (with openssh, there are issues with that when using connection sharing). – Stéphane Chazelas Dec 10 '15 at 14:55

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