nohup(1)
NAME
nohup - run a command immune to hangups
SYNOPSIS
/usr/bin/nohup command [argument...]
/usr/bin/nohup -p [-Fa] pid [pid...]
/usr/bin/nohup -g [-Fa] gpid [gpid...]
/usr/xpg4/bin/nohup command [argument...]
DESCRIPTION
The nohup utility invokes the named command with the argu-
ments supplied. When the command is invoked, nohup arranges
for the SIGHUP signal to be ignored by the process.
When invoked with the -p or -g flags, nohup arranges for
processes already running as identified by a list of process
IDs or a list of process group IDs to become immune to hang-
ups.
The nohup utility can be used when it is known that command
will take a long time to run and the user wants to log out
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 programmati-
cally has chosen to ignore SIGHUP.
/usr/bin/nohup
Processes run by /usr/bin/nohup are immune to SIGHUP
(hangup) and SIGQUIT (quit) signals.
/usr/bin/nohup -p [-Fa]
Processes specified by ID are made immune to SIGHUP
and SIGQUIT, and all output to the controlling termi-
nal is redirected to nohup.out. If -F is specified,
nohup will force control of each process. If -a is
specified, nohup will change the signal disposition of
SIGHUP and SIGQUIT even if the process has installed a
handler for either signal.
/usr/bin/nohup -g [-Fa]
Every process in the same process group as the
processes specified by ID are made immune to SIGHUP
and SIGQUIT, and all output to the controlling termi-
nal is redirected to nohup.out. If -F is specified,
nohup will force control of each process. If -a is
specified, nohup will change the signal disposition of
SIGHUP and SIGQUIT even if the process has installed a
handler for either signal.
/usr/xpg4/bin/nohup
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 $HOME/nohup.out. If a file is
created, the file will have read and write permission
(600, see chmod(1)). If the standard error is a termi-
nal, it is redirected to the standard output, other-
wise it is not redirected. The priority of the process
run by nohup is not altered.
OPTIONS
The following options are supported:
-a Always changes the signal disposition of target
processes. This option is valid only when specified
with -p or -g.
-F Force. Grabs the target processes even if another pro-
cess has control. This option is valid only when
specified with -p or -g.
-g Operates on a list of process groups. This option is
not valid with -p.
-p Operates on a list of processes. This option is not
valid with -g.
OPERANDS
The following operands are supported:
pid A decimal process ID to be manipulated by nohup -p.
pgid A decimal process group ID to be manipulated by nohup
-g.
command
The name of a command that is to be invoked. If the
command operand names any of the special
shell_builtins(1) utilities, the results are unde-
fined.
argument
Any string to be supplied as an argument when invoking
the command operand.
EXAMPLES
Example 1: Applying nohup to pipelines or command lists
It is frequently desirable to apply nohup to pipelines or
lists of commands. This can be done only by placing pipe-
lines and command lists in a single file, called a shell
script. One can then issue:
example$ 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 &
Example 2: Applying nohup -p to a process
example$ long_running_command &
example$ nohup -p `pgrep long_running_command`
Example 3: Applying nohup -g to a process group
example$ make &
example$ ps -o sid -p $$
SID
81079
example$ nohup -g `pgrep -s 81079 make`
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of nohup: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, PATH, NLSPATH, and PATH.
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 those 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.
$HOME/nohup.out
The output file of the nohup execution if standard
output is a terminal and if the current directory is
not writable.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
/usr/bin/nohup
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| CSI | enabled |
|_____________________________|_____________________________|
/usr/xpg4/bin/nohup
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWxcu4 |
|_____________________________|_____________________________|
| CSI | enabled |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
SEE ALSO
batch(1), chmod(1), csh(1), ksh(1), nice(1), pgrep(1),
proc(1), ps(1), sh(1), shell_builtins(1), signal(3C),
proc(4), attributes(5), environ(5), standards(5)
WARNINGS
If you are running the Korn shell (ksh(1)) as your login
shell, and have nohup'ed jobs running when you attempt to
log out, you will be warned with the message:
You have jobs running.
You will then need to log out a second time to actually log
out. However, your background jobs will continue to run.
NOTES
The C-shell (csh(1)) has a built-in command nohup that pro-
vides immunity from SIGHUP, but does not redirect output to
nohup.out. Commands executed with `&' are automatically
immune to HUP signals while in the background.
nohup does not recognize command sequences. In the case of
the following command,
example$ nohup command1; command2
the nohup utility applies only to command1. The command,
example$ nohup (command1; command2)
is syntactically incorrect.
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