bg(1)                                                                    bg(1)


NAME
     bg - run jobs in the background

SYNOPSIS
     bg [job_id ...]

DESCRIPTION
     If job control is enabled (see the description of set -m in the sh(1)
     manpage), the bg utility resumes suspended jobs from the current
     environment by running them as background jobs. If the job specified by
     job_id is already a running background job, the bg utility has no effect
     and will exit successfully.

     Using bg to place a job into the background causes its process ID to
     become "known in the current shell execution environment", as if it had
     been started as an asynchronous list.

OPERANDS
     The following operand is supported:

     job_id    Specify the job to be resumed as a background job. If no job_id
               operand is given, the most recently suspended job is used. The
               format of job_id is described in the entry for job control job
               ID in the (sh) manpage.

STDOUT
     The output of bg consists of a line in the format:

          "[%d] %s\n", <job-number>, <command>

     where the fields are as follows:

     <job-number>      A number that can be used to identify the job to the
                       wait, fg and kill utilities. Using these utilities, the
                       job can be identified by prefixing the job number with
                       "%".

     <command>         The associated command that was given to the shell.

EXIT STATUS
     The following exit values are returned:

     0   Successful completion.

     >0  An error occurred.

CONSEQUENCES OF ERRORS
     If job control is disabled, the bg utility will exit with an error and no
     job will be placed in the background.


APPLICATION USAGE
     A job is generally suspended by typing the SUSP character (<control>Z).
     At that point, bg can put the job into the background. This is most
     effective when the job is expecting no terminal input and its output has
     been redirected to non-terminal files. A background job can be forced to
     stop when it has terminal output by issuing the command:

          stty tostop

     A background job can be stopped with the command:

          kill -s stop job ID

     The bg utility will not work as expected when it is operating in its own
     utility execution environment because that environment will have no
     suspended jobs. In the following examples:

           ... | xargs bg

          (bg)

     each bg operates in a different environment and will not share its parent
     shell's understanding of jobs. For this reason, bg is generally
     implemented as a shell regular built-in.

SEE ALSO
     fg(1), kill(1), jobs(1), sh(1), wait(1).


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