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10 .TH NOHUP 1 "Oct 25, 2017"
11 .SH NAME
12 nohup \- run a command immune to hangups
13 .SH SYNOPSIS
14 .LP
15 .nf
16 \fB/usr/bin/nohup\fR \fIcommand\fR [\fIargument\fR]...
17 .fi
19 .SH DESCRIPTION
20 .sp
21 .LP
22 The \fBnohup\fR utility invokes the named \fIcommand\fR with the arguments
23 supplied. When the \fIcommand\fR is invoked, \fBnohup\fR arranges for the
24 \fBSIGHUP\fR signal to be ignored by the process.
25 .sp
26 .LP
27 When invoked with the \fB-p\fR or \fB-g\fR flags, \fBnohup\fR arranges for
28 processes already running as identified by a list of process \fBID\fRs or a
29 list of process group \fBID\fRs to become immune to hangups.
30 .sp
31 .LP
32 The \fBnohup\fR utility can be used when it is known that \fIcommand\fR takes a
33 long time to run and the user wants to log out of the terminal. When a shell
34 exits, the system sends its children \fBSIGHUP\fR signals, which by default
35 cause them to be killed. All stopped, running, and background jobs ignores
36 \fBSIGHUP\fR and continue running, if their invocation is preceded by the
37 \fBnohup\fR command or if the process programmatically has chosen to ignore
38 \fBSIGHUP\fR.
39 .sp
40 .ne 2
41 .na
42 \fB\fB/usr/bin/nohup\fR\fR
43 .ad
44 .RS 27n
45 Processes run by \fB/usr/bin/nohup\fR are immune to \fBSIGHUP\fR.
46 .sp
47 The \fBnohup\fR utility does not arrange to make processes immune to a
48 \fBSIGTERM\fR (terminate) signal, so unless they arrange to be immune to
49 \fBSIGTERM\fR or the shell makes them immune to \fBSIGTERM\fR, they will
50 receive it.
51 .sp
52 If \fBnohup.out\fR is not writable in the current directory, output is
53 redirected to \fB$HOME/nohup.out\fR. If a file is created, the file has read
54 and write permission (\fB600\fR. See \fBchmod\fR(1). If the standard error is a
55 terminal, it is redirected to the standard output, otherwise it is not
56 redirected. The priority of the process run by \fBnohup\fR is not altered.
57 .RE
59 .SH OPTIONS
60 .sp
61 .LP
62 The following options are supported:
63 .sp
64 .ne 2
65 .na
66 \fB\fB-a\fR\fR
67 .ad
68 .RS 6n
69 Always changes the signal disposition of target processes. This option is valid
70 only when specified with \fB-p\fR or \fB-g\fR.
71 .RE
73 .sp
74 .ne 2
75 .na
76 \fB\fB-F\fR\fR
77 .ad
78 .RS 6n
79 Force. Grabs the target processes even if another process has control. This
80 option is valid only when specified with \fB-p\fR or \fB-g.\fR
81 .RE
83 .sp
84 .ne 2
85 .na
86 \fB\fB-g\fR\fR
87 .ad
88 .RS 6n
89 Operates on a list of process groups. This option is not valid with \fB-p\fR.
90 .RE
92 .sp
93 .ne 2
94 .na
95 \fB\fB-p\fR\fR
96 .ad
97 .RS 6n
98 Operates on a list of processes. This option is not valid with \fB-g\fR.
99 .RE
101 .SH OPERANDS
102 .sp
103 .LP
104 The following operands are supported:
105 .sp
106 .ne 2
107 .na
108 \fB\fIpid\fR\fR
109 .ad
110 .RS 12n
111 A decimal process \fBID\fR to be manipulated by \fBnohup\fR \fB-p\fR.
112 .RE
114 .sp
115 .ne 2
116 .na
117 \fB\fIpgid\fR\fR
118 .ad
119 .RS 12n
120 A decimal process group \fBID\fR to be manipulated by \fBnohup\fR \fB-g\fR.
121 .RE
123 .sp
124 .ne 2
125 .na
126 \fB\fIcommand\fR\fR
127 .ad
128 .RS 12n
129 The name of a command that is to be invoked. If the \fIcommand\fR operand names
130 any of the special \fBshell_builtins\fR(1) utilities, the results are
131 undefined.
132 .RE
134 .sp
135 .ne 2
136 .na
137 \fB\fIargument\fR\fR
138 .ad
139 .RS 12n
140 Any string to be supplied as an argument when invoking the \fIcommand\fR
141 operand.
142 .RE
144 .SH USAGE
145 .sp
146 .LP
147 Caution should be exercised when using the \fB-F\fR flag. Imposing two
148 controlling processes on one victim process can lead to chaos. Safety is
149 assured only if the primary controlling process, typically a debugger, has
150 stopped the victim process and the primary controlling process is doing nothing
151 at the moment of application of the \fBproc\fR tool in question.
152 .SH EXAMPLES
153 .LP
154 \fBExample 1 \fRApplying nohup to pipelines or command lists
155 .sp
156 .LP
157 It is frequently desirable to apply \fBnohup\fR to pipelines or lists of
158 commands. This can be done only by placing pipelines and command lists in a
159 single file, called a shell script. One can then issue:
161 .sp
162 .in +2
163 .nf
164 example$ \fBnohup sh \fIfile\fR\fR
165 .fi
166 .in -2
167 .sp
169 .sp
170 .LP
171 and the \fBnohup\fR applies to everything in \fIfile\fR. If the shell script
172 \fIfile\fR is to be executed often, then the need to type \fBsh\fR can be
173 eliminated by giving \fIfile\fR execute permission.
175 .sp
176 .LP
177 Add an ampersand and the contents of \fIfile\fR are run in the background with
178 interrupts also ignored (see \fBsh\fR(1)):
180 .sp
181 .in +2
182 .nf
183 example$ \fBnohup \fIfile\fR &\fR
184 .fi
185 .in -2
186 .sp
188 .LP
189 \fBExample 2 \fRApplying nohup -p to a process
190 .sp
191 .in +2
192 .nf
193 example$ \fBlong_running_command &\fR
194 example$ \fBnohup -p `pgrep long_running_command`\fR
195 .fi
196 .in -2
197 .sp
199 .LP
200 \fBExample 3 \fRApplying nohup -g to a process group
201 .sp
202 .in +2
203 .nf
204 example$ \fBmake &\fR
205 example$ \fBps -o sid -p $$\fR
206 SID
207 81079
208 example$ \fBnohup -g `pgrep -s 81079 make`\fR
209 .fi
210 .in -2
211 .sp
213 .SH ENVIRONMENT VARIABLES
214 .sp
215 .LP
216 See \fBenviron\fR(5) for descriptions of the following environment variables
217 that affect the execution of \fBnohup\fR: \fBLANG\fR, \fBLC_ALL\fR,
218 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, \fBPATH\fR, \fBNLSPATH\fR, and \fBPATH\fR.
219 .sp
220 .ne 2
221 .na
222 \fB\fBHOME\fR\fR
223 .ad
224 .RS 8n
225 Determine the path name of the user's home directory: if the output file
226 \fBnohup.out\fR cannot be created in the current directory, the \fBnohup\fR
227 command uses the directory named by \fBHOME\fR to create the file.
228 .RE
230 .SH EXIT STATUS
231 .sp
232 .LP
233 The following exit values are returned:
234 .sp
235 .ne 2
236 .na
237 \fB\fB126\fR\fR
238 .ad
239 .RS 7n
240 \fIcommand\fR was found but could not be invoked.
241 .RE
243 .sp
244 .ne 2
245 .na
246 \fB\fB127\fR\fR
247 .ad
248 .RS 7n
249 An error occurred in \fBnohup\fR, or \fIcommand\fR could not be found
250 .RE
252 .sp
253 .LP
254 Otherwise, the exit values of \fBnohup\fR are those of the \fIcommand\fR
255 operand.
256 .SH FILES
257 .sp
258 .ne 2
259 .na
260 \fB\fBnohup.out\fR\fR
261 .ad
262 .RS 19n
263 The output file of the \fBnohup\fR execution if standard output is a terminal
264 and if the current directory is writable.
265 .RE
267 .sp
268 .ne 2
269 .na
270 \fB\fB$HOME/nohup.out\fR\fR
271 .ad
272 .RS 19n
273 The output file of the \fBnohup\fR execution if standard output is a terminal
274 and if the current directory is not writable.
275 .RE
277 .SH ATTRIBUTES
278 .sp
279 .LP
280 See \fBattributes\fR(5) for descriptions of the following attributes:
281 .SS "/usr/bin/nohup"
282 .sp
284 .sp
285 .TS
286 box;
287 c | c
288 l | l .
289 ATTRIBUTE TYPE ATTRIBUTE VALUE
290 _
291 CSI Enabled
292 _
293 Interface Stability Standard
294 .TE
296 .SH SEE ALSO
297 .sp
298 .LP
299 \fBbatch\fR(1), \fBchmod\fR(1), \fBcsh\fR(1), \fBksh\fR(1), \fBnice\fR(1),
300 \fBpgrep\fR(1), \fBproc\fR(1), \fBps\fR(1), \fBsh\fR(1),
301 \fBshell_builtins\fR(1), \fBsignal\fR(3C), \fBproc\fR(4), \fBattributes\fR(5),
302 \fBenviron\fR(5), \fBstandards\fR(5)
303 .SH WARNINGS
304 .sp
305 .LP
306 If you are running the Korn shell (\fBksh\fR(1)) as your login shell, and have
307 \fBnohup\fR'ed jobs running when you attempt to log out, you are warned with
308 the message:
309 .sp
310 .in +2
311 .nf
312 You have jobs running.
313 .fi
314 .in -2
315 .sp
317 .sp
318 .LP
319 You need to log out a second time to actually log out. However, your background
320 jobs continues to run.
321 .SH NOTES
322 .sp
323 .LP
324 The C-shell (\fBcsh\fR(1)) has a built-in command \fBnohup\fR that provides
325 immunity from \fBSIGHUP\fR, but does not redirect output to \fBnohup.out\fR.
326 Commands executed with `\fB&\fR\&' are automatically immune to \fBHUP\fR
327 signals while in the background.
328 .sp
329 .LP
330 \fBnohup\fR does not recognize command sequences. In the case of the following
331 command,
332 .sp
333 .in +2
334 .nf
335 example$ \fBnohup command1; command2\fR
336 .fi
337 .in -2
338 .sp
340 .sp
341 .LP
342 the \fBnohup\fR utility applies only to \fBcommand1\fR. The command,
343 .sp
344 .in +2
345 .nf
346 example$ \fBnohup (command1; command2)\fR
347 .fi
348 .in -2
349 .sp
351 .sp
352 .LP
353 is syntactically incorrect.