I have detached a process from my terminal, like this:
$ process &
That terminal is now long closed, but
process is still running, and I want to send some commands to that process's stdin. Is that possible?
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Yes, it is. First, create a pipe:
Use gdb to attach to the process:
gdb -p PID
Then close stdin:
call close (0); and open it again:
call open ("/tmp/fifo", 0600)
Finally, write away (from a different terminal, as gdb will probably hang):
echo blah > /tmp/fifo
When original terminal is no longer accessible...
reptyr might be what you want, see https://serverfault.com/a/284795/187998
Quote from there:
Have a look at reptyr, which does exactly that. The github page has all the information.
reptyr - A tool for "re-ptying" programs.
reptyr is a utility for taking an existing running program and attaching it to a new terminal. Started a long-running process over ssh, but have to leave and don't want to interrupt it? Just start a screen, use reptyr to grab it, and then kill the ssh session and head on home.
"reptyr PID" will grab the process with id PID and attach it to your current terminal.
After attaching, the process will take input from and write output to the new terminal, including ^C and ^Z. (Unfortunately, if you background it, you will still have to run "bg" or "fg" in the old terminal. This is likely impossible to fix in a reasonable way without patching your shell.)
I am quite sure you can not.
ps x. If a process has a
? as controlling tty, you can not send input to it any more.
9942 ? S 0:00 tail -F /var/log/messages 9947 pts/1 S 0:00 tail -F /var/log/messages
In this example, you can send input to
9947 doing something like
echo "test" > /dev/pts/1. The other process (
9942) is not reachable.
EDIT : As Stephane Gimenez said, it's not that simple. It's only allowing you to print to a different terminal.
You can try to write to this process using /proc. It should be located in /proc/pid/fd/0, so a simple :
echo "hello" > /proc/PID/fd/0
should do it. I have not tried it, but it should work, as long as this process still has a valid stdin file descriptor. You can check it with
ls -l on /proc/pid/fd/.
See nohup for more details about how to keep processes running.
Just ending the command line with
& will not completely detach the process, it will just run it in the background. (With
zsh you can use
&! to actually detach it, otherwise you have do
disown it later).
When a process runs in the background, it won't receive input from its controlling terminal anymore. But you can send it back into the foreground with
fg and then it will read input again.
Otherwise, it's not possible to externally change its filedescriptors (including stdin) or to reattach a lost controlling terminal… unless you use debugging tools (see Ansgar's answer, or have a look at the