# fg

## 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.1‐2017, _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.1‐2017, _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(1p).  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.1‐2017 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.1‐2017 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.
    


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