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Re: A background ssh can take over the tty from bash?
From: |
Clark Wang |
Subject: |
Re: A background ssh can take over the tty from bash? |
Date: |
Mon, 12 Jun 2017 10:24:38 +0800 |
On Mon, Jun 12, 2017 at 5:48 AM, Chet Ramey <chet.ramey@case.edu> wrote:
> On 6/10/17 10:19 AM, Clark Wang wrote:
>
> > If I kill the "ssh -o ControlMaster=no -o ControlPath=/tmp/socket.tmp
> > 127.0.0.1 sleep 9999" then tty #1 (pts/11) would be able to accept my
> input
> > again. Seems like the background "ssh" at tty #1 is consuming all input.
> I
> > cannot understand this since it should be stopped by SIGTTIN if it tries
> to
> > read from the tty.
>
> This has come up before. You need to use `ssh -n' to avoid it reading from
> stdin. Processes can ignore SIGTTIN, and ssh does so to avoid being stopped
> if it reads from the tty while in the background.
>
I've checked the ssh process and it does not catch SIGTTIN and that's why
I'm confused.
$ ps p937
PID TTY STAT TIME COMMAND
937 pts/2 S 0:00 ssh -o ControlMaster=no -o
ControlPath=/tmp/socket.ssh 127.0.0.1 sleep 9999
$ ps s p937
UID PID PENDING BLOCKED IGNORED
CAUGHT STAT TTY TIME COMMAND
0 937 0000000000000000 0000000000000000 0000000000001000
0000000188004003 S pts/2 0:00 ssh -o ControlMaster=no -o
ControlPath=/tmp/socket.ssh 127.0.0.1 sleep 9999
$
The decoded sig masks are:
PENDING (0000000000000000):
BLOCKED (0000000000000000):
IGNORED (0000000000001000):
13 PIPE
CAUGHT (0000000188004003):
1 HUP
2 INT
15 TERM
28 WINCH
32
33
- A background ssh can take over the tty from bash?, Clark Wang, 2017/06/10
- Re: A background ssh can take over the tty from bash?, John McKown, 2017/06/10
- Re: A background ssh can take over the tty from bash?, Chet Ramey, 2017/06/11
- Re: A background ssh can take over the tty from bash?,
Clark Wang <=
- Re: A background ssh can take over the tty from bash?, L A Walsh, 2017/06/12
- Re: A background ssh can take over the tty from bash?, Clark Wang, 2017/06/12
- Re: A background ssh can take over the tty from bash?, L A Walsh, 2017/06/12
- Re: A background ssh can take over the tty from bash?, Clark Wang, 2017/06/13