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 foreground.
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 envi-
ronment''; 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 sus-
pended, placed in the background, or run as a background job shall be used. The format of job_id is described in the Base Defini-
tions 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, Internationalization 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 internationalization variables.
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 arguments).
Determine the locale that should be used to affect the format and contents of diagnostic 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 format:
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 APPLICATION USAGE section for bg . For this reason, fg is generally implemented as a shell regular
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 characteristics
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 volume of IEEE Std 1003.1-2001 to maintain a degree of uniformity with the rest of the KornShell 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 Technol-
ogy -- 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 original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .
/The Open Group 2003 FG(P)