nohup

Run a process that can live beyond the terminal

$ nohup [command] [argument1 argument2 ...]

$ nohup [command] [argument1 argument2 ...] &

$ nohup [path/to/script.sh] &

$ nohup [command] [argument1 argument2 ...] > [path/to/output_file] &

`nohup` COMMAND [ARG...]
or: `nohup` OPTION

COMMAND
    The command to be executed, which will ignore the SIGHUP signal.

[ARG...]
    Optional arguments passed to the `COMMAND`.

`--help`
    Display a help message and exit.

`--version`
    Output version information and exit.

`nohup` (short for "no hang up") is a POSIX command that runs a specified command such that it ignores the SIGHUP (hang-up) signal. This signal is typically sent to a process by the operating system when its controlling terminal is closed or disconnected, which would normally terminate the process. By using `nohup`, long-running processes can continue executing in the background even after the user logs out or the network connection is lost.

When a command is run with `nohup`, its standard output and standard error are, by default, redirected to a file named `nohup.out` in the current directory. If the current directory is not writable, the output is redirected to `$HOME/nohup.out`. Standard input is redirected from `/dev/null`. It's important to note that `nohup` itself does not automatically background the command; to run a process in the background and disconnect from the terminal, one must typically append `&` to the command. This combination makes `nohup` a crucial utility for managing persistent background tasks on remote servers.

• `nohup` does not automatically send a process to the background; you must explicitly append `&` (ampersand) to the command to run it in the background.
• `nohup` primarily handles the SIGHUP signal. Other signals (e.g., SIGTERM, SIGKILL) can still terminate the process.
• Default output redirection to `nohup.out` can lead to large files if not managed. Always consider explicit redirection (`> file.log 2>&1`) for better control.
• Standard input is redirected from `/dev/null`, so interactive commands will not work as expected.

By default, `nohup` redirects standard output and standard error to a file named `nohup.out` in the current working directory. If `nohup.out` cannot be created or is not writable, it attempts to write to `$HOME/nohup.out`. To redirect output to a different file, you must explicitly do so, for example: `nohup command > output.log 2>&1 &`.

`nohup` automatically redirects standard input to `/dev/null`. This means that the command being run with `nohup` will not be able to receive any input from the terminal after it is started. This is generally desired for background processes but is an important consideration for interactive scripts.

`nohup` has been a fundamental utility in Unix-like operating systems since their early days. It addresses the basic need to run processes that persist beyond the lifetime of a user's login session. Its design is simple and effective, predating more complex session management tools like `screen` and `tmux`, but it remains a widely used and essential command for its specific purpose.

`disown(1)`, `screen(1)`, `tmux(1)`, `bg(1)`, `jobs(1)`, `at(1)`