How do I detach a process from Terminal, entirely?

nohup cmd &

nohup detaches the process completely (daemonizes it)

If you are using bash, try disown [jobspec]; see bash(1).

Another approach you can try is at now. If you're not superuser, your permission to use at may be restricted.

Reading these answers, I was under the initial impression that issuing nohup <command> & would be sufficient. Running zsh in gnome-terminal, I found that nohup <command> & did not prevent my shell from killing child processes on exit. Although nohup is useful, especially with non-interactive shells, it only guarantees this behavior if the child process does not reset its handler for the SIGHUP signal.

In my case, nohup should have prevented hangup signals from reaching the application, but the child application (VMWare Player in this case) was resetting its SIGHUP handler. As a result when the terminal emulator exits, it could still kill your subprocesses. This can only be resolved, to my knowledge, by ensuring that the process is removed from the shell's jobs table. If nohup is overridden with a shell builtin, as is sometimes the case, this may be sufficient, however, in the event that it is not...

disown is a shell builtin in bash, zsh, and ksh93,

<command> &
disown

or

<command> &; disown

if you prefer one-liners. This has the generally desirable effect of removing the subprocess from the jobs table. This allows you to exit the terminal emulator without accidentally signaling the child process at all. No matter what the SIGHUP handler looks like, this should not kill your child process.

After the disown, the process is still a child of your terminal emulator (play with pstree if you want to watch this in action), but after the terminal emulator exits, you should see it attached to the init process. In other words, everything is as it should be, and as you presumably want it to be.

What to do if your shell does not support disown? I'd strongly advocate switching to one that does, but in the absence of that option, you have a few choices.

1. screen and tmux can solve this problem, but they are much heavier weight solutions, and I dislike having to run them for such a simple task. They are much more suitable for situations in which you want to maintain a tty, typically on a remote machine.
2. For many users, it may be desirable to see if your shell supports a capability like zsh's setopt nohup. This can be used to specify that SIGHUP should not be sent to the jobs in the jobs table when the shell exits. You can either apply this just before exiting the shell, or add it to shell configuration like ~/.zshrc if you always want it on.
3. Find a way to edit the jobs table. I couldn't find a way to do this in tcsh or csh, which is somewhat disturbing.
4. Write a small C program to fork off and exec(). This is a very poor solution, but the source should only consist of a couple dozen lines. You can then pass commands as commandline arguments to the C program, and thus avoid a process specific entry in the jobs table.

I think screen might solve your problem

1. nohup $COMMAND &

2. $COMMAND & disown

3. setsid command

I've been using number 2 for a very long time, but number 3 works just as well. Also, disown has a 'nohup' flag of '-h', can disown all processes with '-a', and can disown all running processes with '-ar'.

Silencing is accomplished by '$COMMAND &>/dev/null'.

Hope this helps!

in tcsh (and maybe in other shells as well), you can use parentheses to detach the process.

Compare this:

> jobs # shows nothing
> firefox &
> jobs
[1]  + Running                       firefox

To this:

> jobs # shows nothing
> (firefox &)
> jobs # still shows nothing
>

This removes firefox from the jobs listing, but it is still tied to the terminal; if you logged in to this node via 'ssh', trying to log out will still hang the ssh process.

You can run your command using the nohup command, this detach your process and redirects outputs to a given file... but I am not sure that is exactly what you need ..

To disassociate tty shell run command through sub-shell for e.g.

(command)&

When exit used terminal closed but process is still alive.

check -

(sleep 100) & exit

Open other terminal

ps aux | grep sleep

Process is still alive.

Backgrounding and foregrounding a job is probably one of the very first things every Unix sys-admin should know.

Here is how it is done:

./script.sh
# suspend process
{ctrl-Z}
# background process
bg
# list all backgrounded jobs
jobs
# bring it back to foreground
fg

Try daemon -- should be available from your friendly package manager and comprehensively take care of every way of disassociating itself from the terminal.

In my .bashrc, I have these functions for precisely that purpose:

function run_disowned() {
    "$@" & disown
}

function dos() {
    # run_disowned and silenced

    run_disowned "$@" 1>/dev/null 2>/dev/null
}

Prefix a command with dos to run it detached from the terminal.

The function is written to work with bash and zsh.

I use the following script to do this. It stops the process printing to the terminal, detaches with nohup, and exits with the return status if the command finishes within the TIMEOUT.

#!/bin/bash

TIMEOUT=0.1

CMD=( "$@" )
#Could have some shortcuts here, e.g. replace "somefile.c" with "gedit somefile.c"

#use nohup to run the command, suppressing its output and allowing the terminal to be closed
#also send nohup's output to /dev/null, supressing nohup.out
#run nohup in the background so this script doesn't block
#print the command for debugging and to see bash variable expansion
printf "%q " "${CMD[@]}"
echo
nohup "${CMD[@]}" >/dev/null 2>&1 &
NOHUP_PID=$!

#kill this script after a short time, exiting with success status - command is still running
#this is needed as there is no timeout argument for `wait` below
MY_PID=$$
trap "exit 0" SIGINT SIGTERM
sleep $TIMEOUT && kill $MY_PID 2>/dev/null & #ignore "No such process" error if this exits normally

#if the command finishes before the above timeout, everything may be just fine or there could have been an error
wait $NOHUP_PID
NOHUP_STATUS=$?
#print an error if there was any. most commonly, there was a typo in the command
[ $NOHUP_STATUS != 0 ] && echo "Error: $CMD"
#return the exit status of nohup, whatever it was
exit $NOHUP_STATUS

Usage example:

>>> run false
false
Error: false
>>> echo $?
1
>>> run true
true
>>> run sleep 10
sleep 10
>>>

I have found on Mac OS X that I need to use both nohup AND disown to ensure that the child process is not torn down with the terminal.