FG(P) POSIX Programmer's Manual FG(P)
fg - run jobs in the foreground
If job control is enabled (see the description of set -m), the fg utility shall move a
background job from the current environment (see Shell Execution Environment ) into the
Using fg to place a job into the foreground shall remove its process ID from the list of
those "known in the current shell execution environment''; see Asynchronous Lists .
The following operand shall be supported:
job_id Specify the job to be run as a foreground job. If no job_id operand is given, the
job_id for the job that was most recently suspended, placed in the background, or
run as a background job shall be used. The format of job_id is described in the
Base Definitions volume of IEEE Std 1003.1-2001, Section 3.203, Job Control Job ID.
The following environment variables shall affect the execution of fg:
LANG Provide a default value for the internationalization variables that are unset or
null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
nationalization Variables for the precedence of internationalization variables used
to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other interna-
Determine the locale for the interpretation of sequences of bytes of text data as
characters (for example, single-byte as opposed to multi-byte characters in argu-
Determine the locale that should be used to affect the format and contents of diag-
nostic messages written to standard error.
Determine the location of message catalogs for the processing of LC_MESSAGES .
The fg utility shall write the command line of the job to standard output in the following
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
If job control is disabled, the fg utility shall exit with an error and no job shall be
placed in the foreground.
The following sections are informative.
The fg utility does not work as expected when it is operating in its own utility execution
environment because that environment has no applicable jobs to manipulate. See the APPLI-
CATION USAGE section for bg . For this reason, fg is generally implemented as a shell reg-
The extensions to the shell specified in this volume of IEEE Std 1003.1-2001 have mostly
been based on features provided by the KornShell. The job control features provided by bg,
fg, and jobs are also based on the KornShell. The standard developers examined the charac-
teristics of the C shell versions of these utilities and found that differences exist.
Despite widespread use of the C shell, the KornShell versions were selected for this vol-
ume of IEEE Std 1003.1-2001 to maintain a degree of uniformity with the rest of the Korn-
Shell features selected (such as the very popular command line editing features).
Asynchronous Lists , Shell Execution Environment , bg , kill() , jobs , wait()
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 FG(P)