1FG(1P) POSIX Programmer's Manual FG(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 fg — run jobs in the foreground
13
15 fg [job_id]
16
18 If job control is enabled (see the description of set -m), the fg util‐
19 ity shall move a background job from the current environment (see Sec‐
20 tion 2.12, Shell Execution Environment) into the foreground.
21 Using fg to place a job into the foreground shall remove its process ID
23 from the list of those ``known in the current shell execution environ‐
24 ment''; see Section 2.9.3.1, Examples.
25
27 None.
28
30 The following operand shall be supported:
31 job_id Specify the job to be run as a foreground job. If no job_id
33 operand is given, the job_id for the job that was most
34 recently suspended, placed in the background, or run as a
35 background job shall be used. The format of job_id is
36 described in the Base Definitions volume of POSIX.1‐2017,
37 Section 3.204, Job Control Job ID.
38
40 Not used.
41
43 None.
44
46 The following environment variables shall affect the execution of fg:
47 LANG Provide a default value for the internationalization vari‐
49 ables that are unset or null. (See the Base Definitions vol‐
50 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
51 ables for the precedence of internationalization variables
52 used to determine the values of locale categories.)
53 LC_ALL If set to a non-empty string value, override the values of
55 all the other internationalization variables.
56 LC_CTYPE Determine the locale for the interpretation of sequences of
58 bytes of text data as characters (for example, single-byte as
59 opposed to multi-byte characters in arguments).
60 LC_MESSAGES
62 Determine the locale that should be used to affect the format
63 and contents of diagnostic messages written to standard
64 error.
65 NLSPATH Determine the location of message catalogs for the processing
67 of LC_MESSAGES.
68
70 Default.
71
73 The fg utility shall write the command line of the job to standard out‐
74 put in the following format:
75 "%s\n", <command>
78
80 The standard error shall be used only for diagnostic messages.
81
83 None.
84
86 None.
87
89 The following exit values shall be returned:
90 0 Successful completion.
92 >0 An error occurred.
94
96 If job control is disabled, the fg utility shall exit with an error and
97 no job shall be placed in the foreground.
98 The following sections are informative.
100
102 The fg utility does not work as expected when it is operating in its
103 own utility execution environment because that environment has no
104 applicable jobs to manipulate. See the APPLICATION USAGE section for
105 bg. For this reason, fg is generally implemented as a shell regular
106 built-in.
107
109 None.
110
112 The extensions to the shell specified in this volume of POSIX.1‐2017
113 have mostly been based on features provided by the KornShell. The job
114 control features provided by bg, fg, and jobs are also based on the
115 KornShell. The standard developers examined the characteristics of the
116 C shell versions of these utilities and found that differences exist.
117 Despite widespread use of the C shell, the KornShell versions were
118 selected for this volume of POSIX.1‐2017 to maintain a degree of uni‐
119 formity with the rest of the KornShell features selected (such as the
120 very popular command line editing features).
121
123 None.
124
126 Section 2.9.3.1, Examples, Section 2.12, Shell Execution Environment,
127 bg, kill, jobs, wait
128 The Base Definitions volume of POSIX.1‐2017, Section 3.204, Job Control
130 Job ID, Chapter 8, Environment Variables
131
133 Portions of this text are reprinted and reproduced in electronic form
134 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
135 table Operating System Interface (POSIX), The Open Group Base Specifi‐
136 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
137 Electrical and Electronics Engineers, Inc and The Open Group. In the
138 event of any discrepancy between this version and the original IEEE and
139 The Open Group Standard, the original IEEE and The Open Group Standard
140 is the referee document. The original Standard can be obtained online
141 at http://www.opengroup.org/unix/online.html .
142 Any typographical or formatting errors that appear in this page are
144 most likely to have been introduced during the conversion of the source
145 files to man page format. To report such errors, see https://www.ker‐
146 nel.org/doc/man-pages/reporting_bugs.html .
147IEEE/The Open Group 2017 FG(1P)