Redirect STDERR / STDOUT of a process AFTER it'

Question

In the shell you can do redirection, > <, etc., but how about AFTER a program is started?

Here's how I came to ask this question, a program running in the background of my terminal keeps outputting annoying text. It's an important process so I have to open another shell to avoid the text. I'd like to be able to >/dev/null or some other redirection so I can keep working in the same shell.

Answer 1

Redirect output from a running process to another terminal, file or screen:

tty
ls -l /proc/20818/fd
gdb -p 20818

Inside gdb:

p close(1)
p open("/dev/pts/4", 1)
p close(2)
p open("/tmp/myerrlog", 1)
q

Detach a running process from bash terminal and keep it alive:

[Ctrl+z]
bg %1 && disown %1
[Ctrl+d]

Explanation:

20818 - just an example of running process pid
p - print result of gdb command
close(1) - close standard output
/dev/pts/4 - terminal to write to
close(2) - close error output
/tmp/myerrlog - file to write to
q - quit gdb
bg %1 - run stoped job 1 on background
disown %1 - detach job 1 from terminal