Manual page for nohup(1)
nohup - run a command immune to hangups
SYNOPSIS
/usr/bin/nohup
command [ arguments ]
/usr/xpg4/bin/nohup
command [ arguments ]
AVAILABILITY
/usr/bin/nohup
SUNWcsu
/usr/xpg4/bin/nohup
SUNWxcu4
DESCRIPTION
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.
/usr/bin/nohup
Processes run by
/usr/bin/nohup
are immune to
SIGHUP
(hangup) and
SIGQUIT
(quit)
signals.
/usr/xpg4/bin/nohup
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
$HOME/nohup.out.
If a file is created, the file will have read and write permission
(600,
see
chmod.1
If the standard error is a terminal,
it is redirected to the standard output, otherwise it is not redirected.
The priority of the process run by
nohup
is not altered.
OPERANDS
The following operands are supported:
- command
-
The name of a command that is to be invoked. If the
command
operand names any of the special
shell_builtins.1
utilities, the results are undefined.
- arguments
-
Any string to be supplied as an argument when invoking the
command
operand.
EXAMPLES
It is frequently desirable to apply
nohup
to pipelines or lists of commands.
This can be done only by placing pipelines and command lists in a
single file, called a shell script.
One can then issue:
-
example$ 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 &
ENVIRONMENT
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.
EXIT STATUS
The following exit values are returned:
- 126
-
command
was found but could not be invoked.
- 127
-
An error occurred in
nohup,
or
command
could not be found
Otherwise, the exit values of
nohup
will be that of the
command
operand.
FILES
- nohup.out
-
the output file of the
nohup
execution if standard output is a terminal and if the current directory
is writable.
- $HOME/nohup.out
-
the output file of the
nohup
execution if standard output is a terminal and if the current directory
is not writable.
SEE ALSO
batch.1
chmod.1
csh.1
ksh.1
nice.1
sh.1
shell_builtins.1
signal.3c
environ.5
WARNINGS
If you are running the Korn shell (ksh.1
as your login shell, and have nohup'ed jobs running when you
attempt to logout, you will be warned with the message
You have jobs running.
You will then need to logout a second time to actually logout; however, your background
jobs will continue to run.
NOTES
The C-shell (csh.1
has a built-in command
nohup
that provides immunity from
SIGHUP,
but does not redirect output to
nohup.out.
Commands executed with
`&'
are automatically immune to
HUP
signals while in the background.
nohup
does not recognize command sequences.
In the case of the following command
-
example$ nohup command1; command2
nohup
applies only to
command1.
The command
-
example$ nohup (command1; command2)
is syntactically incorrect.
Created by unroff & hp-tools.
© by Hans-Peter Bischof. All Rights Reserved (1997).
Last modified 21/April/97
