If job control is enabled (see the description of set-m), the
fg utility shall move a background job from the current environment
(see ShellExecution 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
environment''; see Asynchronous Lists .
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:
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.)
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 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 built-in.
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
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 original
Standard can be obtained online at http://www.opengroup.org/unix/online.html