How to redirect a running process output to a file and log out

background.sh

ctrl-z
bg

touch /tmp/stdout
touch /tmp/stderr
gdb -p $!

# In GDB
p dup2(open("/tmp/stdout", 1), 1)
p dup2(open("/tmp/stderr", 1), 2)
detach
quit

# Back in shell
disown
logout

I've not seen it done quite like this before. I like it!

It might be a bit cleaner with something like nohup $you_command_and_arguments_here 2>/tmp/stderr 1>/tmp/stdout to avoid the overhead of all the ptrace's that go on in gdb. Also, disown's implementation is defined to be shell-specific (in other words, do what works for your shell), whereas nohup uses system-level commands to abandon it's parent, so you are less likely to have strange side-effects if you try it on a non-bash shell.

Yeah it's definitely cleaner to do it that way, if you're organized :) I would make it even a simpler and just run it in screen or tmux. Though I know I regularly start long-running tasks before realizing how long they are going to take, so this is a quick hack to get around it.

Thomas, I think you missed the point of the gist. This makes sense if you have a process already running and later realize you need to disown it without losing its output. I for one run into this problem often and I really like this solution.

This was linked on Hacker News and in the comments there julian37 pointed out that someone created a bash script to do this called "Dupx".
http://www.isi.edu/~yuri/dupx/

Edit: And of course, thank you to bringing this tool to my attention. Very useful.

@nnutter Got a backup copy of dupx? That link is dead.

Wayback Machine does, https://web.archive.org/web/20170523123913/http://www.isi.edu/~yuri/dupx/