NAME | SYNOPSIS | DESCRIPTION | OPERANDS | EXAMPLES | ENVIRONMENT VARIABLES | EXIT STATUS | FILES | ATTRIBUTES | SEE ALSO | WARNINGS | NOTES
The nohup utility invokes the named command with the arguments supplied. When the command is invoked, nohup
arranges for the SIGHUP
signal to be ignored by the process.
The nohup utility can be used when it is known that command will take a long time to run and the user wants to logout of the terminal; when a shell exits,
the system sends its children SIGHUP
signals, which by default cause them to be killed. All stopped, running, and background jobs will ignore SIGHUP
and continue running, if their invocation is preceded by the nohup command or if the process programmatically has chosen to ignore SIGHUP
.
Processes run by /usr/bin/nohup are immune to SIGHUP
(hangup) and SIGQUIT
(quit) signals.
Processes run by /usr/xpg4/bin/nohup are immune to SIGHUP
.
The nohup utility does not arrange to make processes immune to a SIGTERM
(terminate) signal, so unless they arrange to be immune to SIGTERM
or the shell makes them immune to SIGTERM
, they will receive it.
If nohup.out is not writable in the current directory, output is redirected to $HOME/nohup.out. If a file is created, the file will have read and write permission (600, see chmod(1)). If the standard error is a terminal, it is redirected to the standard output, otherwise it is not redirected. The priority of the process run by nohup is not altered.
The following operands are supported:
The name of a command that is to be invoked. If the command operand names any of the special shell_builtins(1) utilities, the results are undefined.
Any string to be supplied as an argument when invoking the command operand.
It is frequently desirable to apply nohup to pipelines or lists of commands. This can be done only by placing pipelines and command lists in a single file, called a shell script. One can then issue:
example$ nohup sh file |
and the nohup applies to everything in file. If the shell script file is to be executed often, then the need to type sh can be eliminated by giving file execute permission.
Add an ampersand and the contents of file are run in the background with interrupts also ignored (see sh(1)):
example$ nohup file & |
See environ(5) for descriptions of the following environment variables that affect the execution of nohup: LC_CTYPE, LC_MESSAGES, PATH, and NLSPATH.
Determine the path name of the user's home directory: if the output file nohup.out cannot be created in the current directory, the nohup command will use the directory named by HOME to create the file.
The following exit values are returned:
command was found but could not be invoked.
An error occurred in nohup, or command could not be found
Otherwise, the exit values of nohup will be that of the command operand.
the output file of the nohup execution if standard output is a terminal and if the current directory is writable.
the output file of the nohup execution if standard output is a terminal and if the current directory is not writable.
See attributes(5) for descriptions of the following attributes:
batch(1), chmod(1), csh(1), ksh(1), nice(1), sh(1), shell_builtins(1), signal(3C), attributes(5), environ(5), XPG4(5)
If you are running the Korn shell ( ksh(1)) as your login shell, and have nohup'ed jobs running when you attempt to logout, you will be warned with the message
You have jobs running.
You will then need to logout a second time to actually logout; however, your background jobs will continue to run.
The C-shell ( csh(1)) has a built-in command nohup that provides immunity
from SIGHUP
, but does not redirect output to nohup.out. Commands executed with `&' are automatically immune to HUP signals while in the background.
nohup does not recognize command sequences. In the case of the following command,
example$ nohup command1; command2 |
the nohup utility applies only to command1. The command,
example$ nohup (command1; command2) |
is syntactically incorrect.
NAME | SYNOPSIS | DESCRIPTION | OPERANDS | EXAMPLES | ENVIRONMENT VARIABLES | EXIT STATUS | FILES | ATTRIBUTES | SEE ALSO | WARNINGS | NOTES