observing stdout of another process

Question

Here's the hypothetical scenario: I'm running a test script on some hardware attached to box A, which I have root access to. This test script requires minimal user input (flip a switch every half hour or so). About an hour and a half into the test process, I realize that this script takes a long, long time to finish, to the tune of eight hours. Box A is located in a very cold, loud server room that is generally not that fun to physically occupy. Box B is located in my office, where I have a nice comfy chair and an endless supply of hot pockets. I want some way to monitor the output of the process running on box A from an ssh session in box B so I know when to go flip the switch, but I don't want to restart the testing process. Had I known to start with that the test would take so long to finish, I would have just piped its output to a log file and tail'd that file from my box B ssh session. If I know the PID of the process running on box A, is it possible to observe the stdout of that process from another session?

Of course, I could just run vnc on box A and log in from box B to take a look at the output, but that defeats the purpose of this hypothetical, which is to learn more about how process pipes, stdout, and output in general work in a Linux environment.

Thoughts?

Answer 1

http://ingvar.blog.linpro.no/2010/07/10/changing-a-process-file-descriptor-on-the-fly/