I have a situation where I'm not able to run nohup -p <processid> in Linux RHEL 6.6 box it says this option is not supported. I read the manpage and in Linux it had only --help and --version as options in Linux.
Is there any other alternative for nohup -p, to allow an already-running process to survive an exit of the running terminal?
Part of this is easy: To remove a job from your shell's process table, you can use disown.
The part that's not easy is redirecting stdout and stderr away from the TTY. To do that, you can use gdb to take control of the process and tell it to replace stdin, stdout and stderr (note that you'll need to be sure that this is also done on other subprocesses or threads that likewise need to survive the exit operation):
# for an instance of /path/to/program with PID 1234
# note that this is intended to be a transcript of content typed at a prompt -- it isn't a
# working shell script, since the commands after "gdb" are to be run *by gdb*, not the
# shell.
gdb /path/to/program
attach 1234
p dup2(open("/dev/null", 1), 0)
p dup2(open("stdout-file", 1), 1)
p dup2(open("stderr-file", 1), 2)
detach
quit
This has been automated as a tool called dupx.
nohupis generally pretty useless. Redirect stdin, stdout and stderr to a non-TTY source; tell the shell to set the HUP signal up to be discarded, use thedisownbuiltin to remove a job from your shell's process table, and you've accomplished everythingnohupwould otherwise do without needing to use the command.nohup?nohup" has an utterly brain-deadnohup.outredirection target default.