xenial (1) fg.1posix.gz

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PROLOG
       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.


NAME
       fg — run jobs in the foreground


SYNOPSIS
       fg [job_id]


DESCRIPTION
       If  job  control  is  enabled (see the description of set −m), the fg utility shall move a background job
       from the current environment (see Section 2.12, 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 environment''; see Section 2.9.3.1, Examples.


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 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
                 POSIX.1‐2008, Section 3.204, 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 POSIX.1‐2008, 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.

       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 output 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 POSIX.1‐2008 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 POSIX.1‐2008 to maintain 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
       Section 2.9.3.1, Examples, Section 2.12, Shell Execution Environment, bg, kill, jobs, wait

       The Base Definitions volume of POSIX.1‐2008, Section 3.204, Job Control Job ID,  Chapter  8,  Environment
       Variables


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications  Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
       and The Open Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
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       https://www.kernel.org/doc/man-pages/reporting_bugs.html .