FG(P) POSIX Programmer's Manual FG(P)NAMEfg - run jobs in the foreground
SYNOPSISfg [job_id]
DESCRIPTION
If job control is enabled (see the description of set -m), the fg util‐
ity 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 environ‐
ment''; see Asynchronous Lists .
OPTIONS
None.
OPERANDS
The following operand shall be supported:
job_id Specify the job to be run as a foreground job. If no job_id op‐
erand 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.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
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 Vari‐
ables 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.
LC_CTYPE
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).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error.
NLSPATH
Determine the location of message catalogs for the processing of
LC_MESSAGES .
ASYNCHRONOUS EVENTS
Default.
STDOUT
The fg utility shall write the command line of the job to standard out‐
put in the following format:
"%s\n", <command>
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
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.
APPLICATION USAGE
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.
EXAMPLES
None.
RATIONALE
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 char‐
acteristics 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 main‐
tain a degree of uniformity with the rest of the KornShell features
selected (such as the very popular command line editing features).
FUTURE DIRECTIONS
None.
SEE ALSO
Asynchronous Lists , Shell Execution Environment , bg , kill() , jobs ,
wait()COPYRIGHT
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 .
IEEE/The Open Group 2003 FG(P)
