JOBS(1) User Commands JOBS(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...


ksh93
jobs [-lnp] [job_id...]


fg [job_id...]


bg [job_id...]


DESCRIPTION


sh
When Job Control is enabled, the Bourne shell built-in jobs reports all
jobs that are stopped or executing in the background. If %job_id is
omitted, all jobs that are stopped or running in the background is
reported. The following options modify or 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.h(3HEAD)).


Every job that the shell starts is assigned a positive integer, called a
job_id number which is tracked by the shell and are 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 can be specified in any of the following formats:

% 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 cannot
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 background 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 information.


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 (typically 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 command. The job
most recently stopped (or put into the background if none are stopped) is
referred to as the current job and is indicated with a `+'. The previous
job is indicated 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 percent 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 command 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 foreground.


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 notifies 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 termination 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 specified, the status information for all jobs are displayed.


The following options modify or 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 process id was 1234.


If you are running a job and wish to do something else you can hit the
key ^Z (Control-Z) which sends a STOP signal to the current job. The
shell then normally indicates 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 specified 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 are warned that `You have stopped (running) jobs.' You can use the
jobs command to see what they are. If you do this or immediately try to
exit again, the shell does not warn you a second time, and the stopped
jobs are terminated.


fg moves a background job from the current environment into the
foreground. Using fg to place a job in the foreground removes 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
control. 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 exits 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).

ksh93
jobs displays information about specified jobs that were started by the
current shell environment on standard output. The information contains
the job number enclosed in [...], the status, and the command line that
started the job.


If job_id is omitted, jobs displays the status of all stopped jobs,
background jobs, and all jobs whose status has changed since last
reported by the shell.


When jobs reports the termination status of a job, the shell removes the
job from the list of known jobs in the current shell environment.


The following options modify or enhances the output of jobs:

-l
Displays process IDs after the job number in addition to the usual
information.


-n
Displays only the jobs whose status has changed since the last
prompt was displayed.


-p
Displays the process group leader IDs for the specified jobs.


job_id can be specified to jobs, fg, and bg as one of the following:

number
The process id of job.


-number
The process group id of job.


%number
The job number.


%string
The job whose name begins with string.


%?string
The job whose name contains string.


%+
%%
The current job.


%-
The previous job.


fg places the specified jobs into the foreground in sequence and sends a
CONT signal to start each running. If job_id is omitted, the most
recently started or stopped background job is moved to the foreground.


bg places the specified jobs into the background and sends a CONT signal
to start them running. If job_id is omitted, the most recently started or
stopped background job is resumed or continued in the background.

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 is a
suspended job. If there are at least two suspended jobs,
then the previous job is also 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 prefixing 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
Indicates that the job was 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 can substitute the string Suspended in
place of Stopped. If the job was terminated by a signal,
the format of state is unspecified, but it is visibly
distinct from all of the other state formats shown here and
indicates the name or description of the signal causing the
termination.


command
The associated command that was specified to the shell.


If the -l option is specified, a field containing the process group ID is
inserted before the state field. Also, more processes in a process group
can be output on separate lines, using only the process ID and command
fields.

ENVIRONMENT VARIABLES


See environ(7) 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


sh, csh, ksh
The following exit values are returned for jobs, fg, and bg:

0
Successful completion.


>0
An error occurred.


ksh93
The following exit values are returned for jobs:

0
The information for each job is written to standard output.


>0
One or more jobs does not exist.


The following exit values are returned for fg:

exit status of last job
One or more jobs has been brought into the
foreground.


non-zero
One or more jobs does not exist or has
completed.


The following exit values are returned for bg:

0
All background jobs are started.


>0
One more jobs does not exist or there are no background jobs.


ATTRIBUTES


See attributes(7) for descriptions of the following attributes:

csh, sh, ksh


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|Standard | See standards(7). |
+--------------------+-------------------+

ksh93


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Uncommitted |
+--------------------+-----------------+

SEE ALSO


csh(1), kill(1), ksh(1), ksh93(1), ps(1), sh(1), shell_builtins(1),
stop(1), stty(1), wait(1), signal.h(3HEAD), attributes(7), environ(7),
standards(7)


November 2, 2007 JOBS(1)