nohup(1) manual page
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nohup - run a command immune to hangups
/usr/bin/nohup
command [ arguments ]
/usr/xpg4/bin/nohup command [ arguments ]
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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.
nohup
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
.
nohup 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 $HOME
/nohup.out.
If a file is created, the file will have read and write permission (600,
see chmod(1)
). If the standard error is a terminal, it is redirected to
the standard output, otherwise it is not redirected. The priority of the
process run by nohup is not altered.
The following operands are
supported:
- command
- The name of a command that is to be invoked. If the
command operand names any of the special shell_builtins(1)
utilities, the
results are undefined.
- arguments
- Any string to be supplied as an argument
when invoking the command operand.
It is frequently desirable to
apply nohup to pipelines or lists of commands. This can be done only by
placing pipelines and command lists in a single file, called a shell script.
One can then issue:
example$ 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
.
- HOME
- 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.
- nohup.out
- the output file
of the nohup execution if standard output is a terminal and if the current
directory is writable.
- $HOME/nohup.out
- the output file of the nohup execution
if standard output is a terminal and if the current directory is not writable.
batch(1)
, chmod(1)
, csh(1)
, ksh(1)
, nice(1)
, sh(1)
, shell_builtins(1)
,
signal(3C)
, environ(5)
If you are running the Korn shell (ksh(1)
)
as your login shell, and have nohup’ed jobs running when you attempt to
logout, you will be warned with the message
You have jobs running.
You will
then need to logout a second time to actually logout; however, your background
jobs will continue to run.
The C-shell (csh(1)
) has a built-in command
nohup that provides immunity from SIGHUP
, but does not redirect output
to nohup.out. Commands executed with ‘&’ are automatically immune to HUP
signals
while in the background.
nohup does not recognize command sequences. In the
case of the following command
example$ nohup command1; command2
nohup applies
only to command1. The command
example$ nohup (command1; command2)
is syntactically
incorrect.
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