1NOHUP(P) POSIX Programmer's Manual NOHUP(P)
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6 nohup - invoke a utility immune to hangups
7
9 nohup utility [argument...]
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12 The nohup utility shall invoke the utility named by the utility operand
13 with arguments supplied as the argument operands. At the time the named
14 utility is invoked, the SIGHUP signal shall be set to be ignored.
15 If the standard output is a terminal, all output written by the named
17 utility to its standard output shall be appended to the end of the file
18 nohup.out in the current directory. If nohup.out cannot be created or
19 opened for appending, the output shall be appended to the end of the
20 file nohup.out in the directory specified by the HOME environment vari‐
21 able. If neither file can be created or opened for appending, utility
22 shall not be invoked. If a file is created, the file's permission bits
23 shall be set to S_IRUSR | S_IWUSR.
24 If the standard error is a terminal, all output written by the named
26 utility to its standard error shall be redirected to the same file
27 descriptor as the standard output.
28
30 None.
31
33 The following operands shall be supported:
34 utility
36 The name of a utility that is to be invoked. If the utility op‐
37 erand names any of the special built-in utilities in Special
38 Built-In Utilities , the results are undefined.
39 argument
41 Any string to be supplied as an argument when invoking the util‐
42 ity named by the utility operand.
43
46 Not used.
47
49 None.
50
52 The following environment variables shall affect the execution of
53 nohup:
54 HOME Determine the pathname of the user's home directory: if the out‐
56 put file nohup.out cannot be created in the current directory,
57 the nohup utility shall use the directory named by HOME to cre‐
58 ate the file.
59 LANG Provide a default value for the internationalization variables
61 that are unset or null. (See the Base Definitions volume of
62 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
63 ables for the precedence of internationalization variables used
64 to determine the values of locale categories.)
65 LC_ALL If set to a non-empty string value, override the values of all
67 the other internationalization variables.
68 LC_CTYPE
70 Determine the locale for the interpretation of sequences of
71 bytes of text data as characters (for example, single-byte as
72 opposed to multi-byte characters in arguments).
73 LC_MESSAGES
75 Determine the locale that should be used to affect the format
76 and contents of diagnostic messages written to standard error.
77 NLSPATH
79 Determine the location of message catalogs for the processing of
80 LC_MESSAGES .
81 PATH Determine the search path that is used to locate the utility to
83 be invoked. See the Base Definitions volume of
84 IEEE Std 1003.1-2001, Chapter 8, Environment Variables.
85
88 The nohup utility shall take the standard action for all signals except
89 that SIGHUP shall be ignored.
90
92 If the standard output is not a terminal, the standard output of nohup
93 shall be the standard output generated by the execution of the utility
94 specified by the operands. Otherwise, nothing shall be written to the
95 standard output.
96
98 If the standard output is a terminal, a message shall be written to the
99 standard error, indicating the name of the file to which the output is
100 being appended. The name of the file shall be either nohup.out or
101 $HOME/nohup.out.
102
104 If the standard output is a terminal, all output written by the named
105 utility to the standard output and standard error is appended to the
106 file nohup.out, which is created if it does not already exist.
107
109 None.
110
112 The following exit values shall be returned:
113 126 The utility specified by utility was found but could not be
115 invoked.
116 127 An error occurred in the nohup utility or the utility specified
118 by utility could not be found.
119 Otherwise, the exit status of nohup shall be that of the utility speci‐
122 fied by the utility operand.
123
125 Default.
126 The following sections are informative.
128
130 The command, env, nice, nohup, time, and xargs utilities have been
131 specified to use exit code 127 if an error occurs so that applications
132 can distinguish "failure to find a utility" from "invoked utility
133 exited with an error indication". The value 127 was chosen because it
134 is not commonly used for other meanings; most utilities use small val‐
135 ues for "normal error conditions" and the values above 128 can be con‐
136 fused with termination due to receipt of a signal. The value 126 was
137 chosen in a similar manner to indicate that the utility could be found,
138 but not invoked. Some scripts produce meaningful error messages differ‐
139 entiating the 126 and 127 cases. The distinction between exit codes 126
140 and 127 is based on KornShell practice that uses 127 when all attempts
141 to exec the utility fail with [ENOENT], and uses 126 when any attempt
142 to exec the utility fails for any other reason.
143
145 It is frequently desirable to apply nohup to pipelines or lists of com‐
146 mands. This can be done by placing pipelines and command lists in a
147 single file; this file can then be invoked as a utility, and the nohup
148 applies to everything in the file.
149 Alternatively, the following command can be used to apply nohup to a
151 complex command:
152 nohup sh -c 'complex-command-line'
155
157 The 4.3 BSD version ignores SIGTERM and SIGHUP, and if ./nohup.out can‐
158 not be used, it fails instead of trying to use $HOME/nohup.out.
159 The csh utility has a built-in version of nohup that acts differently
161 from the nohup defined in this volume of IEEE Std 1003.1-2001.
162 The term utility is used, rather than command, to highlight the fact
164 that shell compound commands, pipelines, special built-ins, and so on,
165 cannot be used directly. However, utility includes user application
166 programs and shell scripts, not just the standard utilities.
167 Historical versions of the nohup utility use default file creation
169 semantics. Some more recent versions use the permissions specified here
170 as an added security precaution.
171 Some historical implementations ignore SIGQUIT in addition to SIGHUP;
173 others ignore SIGTERM. An early proposal allowed, but did not require,
174 SIGQUIT to be ignored. Several reviewers objected that nohup should
175 only modify the handling of SIGHUP as required by this volume of
176 IEEE Std 1003.1-2001.
177
179 None.
180
182 Shell Command Language , sh , the System Interfaces volume of
183 IEEE Std 1003.1-2001, signal()
184
186 Portions of this text are reprinted and reproduced in electronic form
187 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
188 -- Portable Operating System Interface (POSIX), The Open Group Base
189 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
190 Electrical and Electronics Engineers, Inc and The Open Group. In the
191 event of any discrepancy between this version and the original IEEE and
192 The Open Group Standard, the original IEEE and The Open Group Standard
193 is the referee document. The original Standard can be obtained online
194 at http://www.opengroup.org/unix/online.html .
195IEEE/The Open Group 2003 NOHUP(P)