NOHUP(1)NOHUP(1)NAMEnohup - 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 arguments sup‐
plied. When the command is invoked, nohup arranges for the SIGHUP sig‐
nal 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 hangups.
The nohup utility can be used when it is known that command takes 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 ignores SIGHUP and continue running, if their invocation is pre‐
ceded by the nohup command or if the process programmatically has cho‐
sen to ignore SIGHUP.
/usr/bin/nohup
Processes run by /usr/bin/nohup are immune
to SIGHUP (hangup) and SIGQUIT (quit) sig‐
nals.
/usr/bin/nohup -p [-Fa]
Processes specified by ID are made immune to
SIGHUP and SIGQUIT, and all output to the
controlling terminal is redirected to
nohup.out. If -F is specified, nohup forces
control of each process. If -a is specified,
nohup changes 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 terminal is redirected to
nohup.out. If -F is specified, nohup forces
control of each process. If -a is specified,
nohup changes 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
$HOME/nohup.out. If a file is created, the
file has read and write permission (600. See
chmod(1). If the standard error is a termi‐
nal, it is redirected to the standard out‐
put, otherwise it is not redirected. The
priority of the process run by nohup is not
altered.
OPTIONS
The following options are supported:
-a
Always changes the signal disposition of target processes. This
option is valid only when specified with -p or -g.
-F
Force. Grabs the target processes even if another process has
control. This option is valid only when specified with -p or -g.
-g
Operates on a list of process groups. This option is not valid
with -p.
-p
Operates on a list of processes. This option is not valid with
-g.
OPERANDS
The following operands are supported:
pid
A decimal process ID to be manipulated by nohup-p.
pgid
A decimal process group ID to be manipulated by nohup-g.
command
The name of a command that is to be invoked. If the command
operand names any of the special shell_builtins(1) utili‐
ties, the results are undefined.
argument
Any string to be supplied as an argument when invoking the
command operand.
USAGE
Caution should be exercised when using the -F flag. Imposing two con‐
trolling processes on one victim process can lead to chaos. Safety is
assured only if the primary controlling process, typically a debugger,
has stopped the victim process and the primary controlling process is
doing nothing at the moment of application of the proc tool in ques‐
tion.
EXAMPLES
Example 1 Applying nohup to pipelines or command lists
It is frequently desirable to apply nohup to pipelines or lists of com‐
mands. This can be done only by placing pipelines and command lists in
a single file, called a shell script. One can then issue:
example$ 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 &
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_MES‐
SAGES, 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 direc‐
tory, the nohup command uses 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 are 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.
$HOME/nohup.out
The output file of the nohup execution if standard
output is a terminal and if the current directory is
not writable.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
/usr/bin/nohup
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│CSI │ Enabled │
└───────────────┴─────────────────┘
/usr/xpg4/bin/nohup
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│CSI │ Enabled │
├────────────────────┼─────────────────┤
│Interface Stability │ Standard │
└────────────────────┴─────────────────┘
SEE ALSObatch(1), chmod(1), csh(1), ksh(1), nice(1), pgrep(1), proc(1), ps(1),
sh(1), shell_builtins(1), signal(3C), proc(4), attributes(5), envi‐
ron(5), standards(5)WARNINGS
If you are running the Korn shell (ksh(1)) as your login shell, and
have nohup'ed jobs running when you attempt to log out, you are warned
with the message:
You have jobs running.
You need to log out a second time to actually log out. However, your
background jobs continues to run.
NOTES
The C-shell (csh(1)) has a built-in command nohup that provides immu‐
nity from SIGHUP, but does not redirect output to nohup.out. Commands
executed with `&' are automatically immune to HUP signals while in the
background.
nohup does not recognize command sequences. In the case of the follow‐
ing command,
example$ nohup command1; command2
the nohup utility applies only to command1. The command,
example$ nohup (command1; command2)
is syntactically incorrect.
Jun 19, 2006 NOHUP(1)
