On Fri, Oct 21, 2022 at 03:50:41PM +0200, Solene Rapenne wrote:
> hi
>
> I found a weird behavior trying to use timeout(1) in a script with
> interactive commands. My use case is to ask for unlocking /home
> from /etc/rc.local but continue if I don't type it in time.
>
> this is working:
>
> timeout 2s less /etc/fstab
>
> the same command isn't working from a script, running it get stuck and
> can't be stopped with ctrl+C
>
> #!/bin/sh
> timeout 2s less /etc/fstab
Using bash(1) or an interactive ksh(1) runs the pager and terminates it
after two seconds:
$ bash -c 'timeout 2s less /etc/fstab'
$ ksh -ic 'timeout 2s less /etc/fstab'
In a non-interactive sh/ksh, GNU's implementation cannot be interrupted,
either, but it does deliver SIGTERM as expected:
# pkg_add coretutils
quirks-6.42 signed on 2022-10-22T00:59:54Z
coreutils-9.1: ok
$ time sh -c 'gtimeout 2s less /etc/fstab'
^C^C
0m02.02s real 0m00.00s user 0m00.03s system
> However, using timeout with a non interactive command in a script
> doesn't create troubles
I haven't looked into this yet, but two things seem worth noting now:
First, non-interactive sh/ksh receives ^C/SIGINT but does not deliver it
to its child proces like interactive shells do, e.g.
$ sh -c 'timeout 2s less /etc/fstab'
^C^C
does nothing.
Secondly, interrupting our timeout(1) directly does not terminate:
$ pgrep -fl fstab
89054 less /etc/fstab
49950 timeout 100s less /etc/fstab
54620 sh -c timeout 100s less /etc/fstab
$ kill -INT 49950
$ kill -TERM 49950
$ kill -QUIT 49950
$ pgrep -fl fstab
89054 less /etc/fstab
49950 timeout 100s less /etc/fstab
54620 sh -c timeout 100s less /etc/fstab
> in the issue case, a ktrace gives the following last lines, but I don't
> know how to interpret them
>
> 21097 timeout PSIG SIGCHLD caught handler=0xb1d715d6b00
> mask=0x86007<SIGHUP|SIGINT|SIGQUIT|SIGALRM|SIGTERM|SIGCHLD>
> 21097 timeout RET sigsuspend -1 errno 4 Interrupted system call
> 21097 timeout CALL sigreturn(0x7f7ffffe3540)
> 21097 timeout RET sigreturn JUSTRETURN
> 21097 timeout CALL kbind(0x7f7ffffe3868,24,0xd30add790970a7bd)
> 21097 timeout RET kbind 0
> 21097 timeout CALL wait4(WAIT_ANY,0x7f7ffffe39f4,0<>,0)
>
