fg(1)
NAME
jobs, fg, bg, stop, notify - control process execution
SYNOPSIS
sh
jobs [-p | -l] [ % job_id...]
jobs -x command [arguments]
fg [ % job_id...]
bg [ % job_id...]
stop % job_id...
stop pid...
csh
jobs [-l]
fg [ % job_id]
bg [ % job_id...]
notify [ % job_id]...
stop % job_id...
stop pid...
ksh
jobs [-lnp] [ % job_id...]
fg [ % job_id...]
bg [ % job_id...]
stop % job_id...
stop pid...
DESCRIPTION
sh
When Job Control is enabled, the Bourne shell built-in jobs
reports all jobs that are stopped or executing in the back-
ground. If %job_id is omitted, all jobs that are stopped or
running in the background will be reported. The following
options will modify/enhance the output of jobs:
-l Reports the process group ID and working directory of
the jobs.
-p Reports only the process group ID of the jobs.
-x Replaces any job_id found in command or arguments with
the corresponding process group ID, and then executes
command passing it arguments.
When the shell is invoked as jsh, Job Control is enabled in
addition to all of the functionality described previously
for sh. Typically Job Control is enabled for the interactive
shell only. Non-interactive shells typically do not benefit
from the added functionality of Job Control.
With Job Control enabled every command or pipeline the user
enters at the terminal is called a job_id. All jobs exist in
one of the following states: foreground, background or
stopped. These terms are defined as follows:
1. A job in the foreground has read and write access to the
controlling terminal.
2. A job in the background is denied read access and has
conditional write access to the controlling terminal (see
stty(1))
3. A stopped job is a job that has been placed in a
suspended state, usually as a result of a SIGTSTP signal
(see signal(3HEAD)).
Every job that the shell starts is assigned a positive
integer, called a job_id number which is tracked by the
shell and will be used as an identifier to indicate a
specific job. Additionally, the shell keeps track of the
current and previous jobs. The current job is the most
recent job to be started or restarted. The previous job is
the first non-current job.
The acceptable syntax for a Job Identifier is of the form:
%job_id
where job_id may be specified in any of the following for-
mats:
% or +
for the current job
- for the previous job
?<string>
specify the job for which the command line uniquely
contains string.
n for job number n, where n is a job number
pref where pref is a unique prefix of the command name (for
example, if the command ls -l name were running in the
background, it could be referred to as %ls); pref can-
not contain blanks unless it is quoted.
When Job Control is enabled, fg resumes the execution of a
stopped job in the foreground, also moves an executing back-
ground job into the foreground. If %job_id is omitted the
current job is assumed.
When Job Control is enabled, bg resumes the execution of a
stopped job in the background. If %job_id is omitted the
current job is assumed.
stop stops the execution of a background job(s) by using its
job_id, or of any process by using its pid; see ps(1).
csh
The C shell built-in, jobs, without an argument, lists the
active jobs under job control.
-l List process IDs, in addition to the normal informa-
tion.
The shell associates a numbered job_id with each command
sequence to keep track of those commands that are running in
the background or have been stopped with TSTP signals (typi-
cally <Control-Z>). When a command or command sequence
(semicolon-separated list) is started in the background
using the & metacharacter, the shell displays a line with
the job number in brackets and a list of associated process
numbers:
[1] 1234
To see the current list of jobs, use the jobs built-in com-
mand. The job most recently stopped (or put into the back-
ground if none are stopped) is referred to as the current
job and is indicated with a `+'. The previous job is indi-
cated with a `-'; when the current job is terminated or
moved to the foreground, this job takes its place (becomes
the new current job).
To manipulate jobs, refer to the bg, fg, kill, stop, and %
built-in commands.
A reference to a job begins with a `%'. By itself, the per-
cent sign refers to the current job.
% %+ %%
The current job.
%- The previous job.
%j Refer to job j as in: `kill -9 %j'. j can be a job
number, or a string that uniquely specifies the com-
mand line by which it was started; `fg %vi' might
bring a stopped vi job to the foreground, for
instance.
%?string
Specify the job for which the command line uniquely
contains string.
A job running in the background stops when it attempts to
read from the terminal. Background jobs can normally produce
output, but this can be suppressed using the `stty tostop'
command.
fg brings the current or specified job_id into the fore-
ground.
bg runs the current or specified jobs in the background.
stop stops the execution of a background job(s) by using its
job_id, or of any process by using its pid; see ps(1).
notify will notify the user asynchronously when the status
of the current job or specified jobs changes.
ksh
jobs displays the status of the jobs that were started in
the current shell environment. When jobs reports the termi-
nation status of a job, the shell removes its process ID
from the list of those "known in the current shell execution
environment."
job_id specifies the jobs for which the status is to be
displayed. If no job_id is given, the status information for
all jobs will be displayed.
The following options will modify/enhance the output of
jobs:
-l (The letter ell.) Provides more information about each
job listed. This information includes the job number,
current job, process group ID, state and the command
that formed the job.
-n Displays only jobs that have stopped or exited since
last notified.
-p Displays only the process IDs for the process group
leaders of the selected jobs.
By default, jobs displays the status of all the stopped
jobs, running background jobs, and all jobs whose status has
changed and have not been reported by the shell.
If the monitor option of the set command is turned on, an
interactive shell associates a job with each pipeline. It
keeps a table of current jobs, printed by the jobs command,
and assigns them small integer numbers. When a job is
started asynchronously with &, the shell prints a line which
looks like:
[1] 1234
indicating that the job, which was started asynchronously,
was job number 1 and had one (top-level) process, whose pro-
cess id was 1234.
If you are running a job and wish to do something else you
may hit the key <^Z> (<Control-Z>) which sends a STOP signal
to the current job. The shell will then normally indicate
that the job has been "Stopped" (see OUTPUT below), and
print another prompt. You can then manipulate the state of
this job, putting it in the background with the bg command,
or run some other commands and then eventually bring the job
back into the foreground with the foreground command fg. A
<^Z> takes effect immediately and is like an interrupt, in
that pending output and unread input are discarded when it
is typed.
There are several ways to refer to jobs in the shell. A job
can be referred to by the process id of any process of the
job or by one of the following:
%number
The job with the given number.
%string
Any job whose command line begins with string; works
only in the interactive mode when the history file is
active.
%?string
Any job whose command line contains string; works only
in the interactive mode when the history file is
active.
%% Current job.
%+ Equivalent to %%.
%- Previous job.
The shell learns immediately whenever a process changes
state. It normally informs you whenever a job becomes
blocked so that no further progress is possible, but only
just before it prints a prompt. This is done so that it does
not otherwise disturb your work. When the monitor mode is
on, each background job that completes triggers any trap set
for CHLD. When you try to leave the shell while jobs are
running or stopped, you will be warned that `You have
stopped (running) jobs.' You may use the jobs command to see
what they are. If you do this or immediately try to exit
again, the shell will not warn you a second time, and the
stopped jobs will be terminated.
fg will move a background job from the current environment
into the foreground. Using fg to place a job in the fore-
ground will remove its process ID from the list of those
"known in the current shell execution environment." The fg
command is available only on systems that support job con-
trol. If job_id is not specified, the current job is brought
into the foreground.
bg 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, bg 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. The bg command is available
only on systems that support job control. If job_id is not
specified, the current job is placed in the background.
stop stops the execution of a background job(s) by using its
job_id, or of any process by using its pid. See ps(1).
OUTPUT
If the -p option is specified, the output consists of one
line for each process ID:
"%d\n", "process ID"
Otherwise, if the -l option is not specified, the output is
a series of lines of the form:
"[%d] %c %s %s\n", job-number, current, state, command
where the fields are as follows:
current
The character + identifies the job that would be used
as a default for the fg or bg commands. This job can
also be specified using the job_id %+ or %% . The
character - identifies the job that would become the
default if the current default job were to exit; this
job can also be specified using the job_id %- . For
other jobs, this field is a space character. At most,
one job can be identified with + and at most one job
can be identified with -. If there is any suspended
job, then the current job will be a suspended job. If
there are at least two suspended jobs, then the previ-
ous job will also be a suspended job.
job-number
A number that can be used to identify the process
group to the wait, fg, bg, and kill utilities. Using
these utilities, the job can be identified by prefix-
ing the job number with %.
state One of the following strings (in the POSIX Locale):
Running
Indicates that the job has not been suspended by a
signal and has not exited.
Done Indicates that the job completed and returned exit
status zero.
Done(code)
Indicates that the job completed normally and that it
exited with the specified non-zero exit status, code,
expressed as a decimal number.
Stopped
Stopped(SIGTSTP)
Indicates that the job was suspended by the SIGTSTP
signal.
Stopped(SIGSTOP)
Indicates that the job was suspended by the SIGSTOP
signal.
Stopped(SIGTTIN)
Indicates that the job was suspended by the SIGTTIN
signal.
Stopped(SIGTTOU)
Indicates that the job was suspended by the SIGTTOU
signal.
The implementation may substitute the string Suspended in
place of Stopped. If the job was terminated by a signal, the
format of state is unspecified, but it will be visibly dis-
tinct from all of the other state formats shown here and
will indicate the name or description of the signal causing
the termination.
command
The associated command that was given to the shell.
If the -l option is specified, a field containing the pro-
cess group ID is inserted before the state field. Also, more
processes in a process group may be output on separate
lines, using only the process ID and command fields.
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of jobs, fg, and bg:
LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.
EXIT STATUS
The following exit values are returned for jobs, fg, and bg:
0 Successful completion.
>0 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
SEE ALSO
csh(1), kill(1), ksh(1), ps(1), sh(1), stop(1),
shell_builtins(1), stty(1), wait(1), signal(3HEAD), attri-
butes(5), environ(5), standards(5)
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