JOBS
Section: POSIX Programmer's Manual (1P)
Updated: 2013
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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
jobs
--- display status of jobs in the current session
SYNOPSIS
jobs [-l|-p] [job_id...]
DESCRIPTION
The
jobs
utility shall display the status of jobs that were started in the
current shell environment; see
Section 2.12,
Shell Execution Environment.
When
jobs
reports the termination status of a job, the shell 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
The
jobs
utility shall conform to the Base Definitions volume of POSIX.1-2008,
Section 12.2,
Utility Syntax Guidelines.
The following options shall be supported:
- -l
-
(The letter ell.) Provide more information about each job listed. This
information shall include the job number, current job, process group
ID, state, and the command that formed the job.
- -p
-
Display only the process IDs for the process group leaders of the
selected jobs.
By default, the
jobs
utility shall display the status of all stopped jobs, running
background jobs and all jobs whose status has changed and have not been
reported by the shell.
OPERANDS
The following operand shall be supported:
- 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 shall be displayed. 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
jobs:
- 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 and
informative messages written to standard output.
- NLSPATH
-
Determine the location of message catalogs for the processing of
LC_MESSAGES.
ASYNCHRONOUS EVENTS
Default.
STDOUT
If the
-p
option is specified, the output shall consist of one line for each
process ID:
-
"%d\n", <process ID>
Otherwise, if the
-l
option is not specified, the output shall be a series of lines of the
form:
-
"[%d] %c %s %s\n", <job-number>, <current>, <state>, <command>
where the fields shall be as follows:
- <current>
-
The character
'+'
identifies the job that would be used as a default for the
fg
or
bg
utilities; this job can also be specified using the
job_id
%+ or
dq%%dq.
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>.
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 shall be a
suspended job. If there are at least two suspended jobs, then the
previous job also shall 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
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 suspended by the SIGTSTP signal.
- 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 shall be visibly distinct from all of the other
<state> formats shown here and shall 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 process group ID shall be
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.
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
Default.
The following sections are informative.
APPLICATION USAGE
The
-p
option is the only portable way to find out the process group of a job
because different implementations have different strategies for
defining the process group of the job. Usage such as $(
jobs
-p)
provides a way of referring to the process group of the job in an
implementation-independent way.
The
jobs
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,
jobs
is generally implemented as a shell regular built-in.
EXAMPLES
None.
RATIONALE
Both
dq%%dq
and
dq%+dq
are used to refer to the current job. Both forms are of equal
validity---the
dq%%dq
mirroring
dq$$dq
and
dq%+dq
mirroring the output of
jobs.
Both forms reflect historical practice of the KornShell and the C shell
with job control.
The job control features provided by
bg,
fg,
and
jobs
are 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).
The
jobs
utility is not dependent on the job control option, as are the
seemingly related
bg
and
fg
utilities because
jobs
is useful for examining background jobs, regardless of the condition of
job control. When the user has invoked a
set
+m
command and job control has been turned off,
jobs
can still be used to examine the background jobs associated with that
current session. Similarly,
kill
can then be used to kill background jobs with
kill
%<
background job number>.
The output for terminated jobs is left unspecified to accommodate
various historical systems. The following formats have been witnessed:
- 1.
-
Killed(signal name)
- 2.
-
signal name
- 3.
-
signal name(coredump)
- 4.
-
signal description-
core dumped
Most users should be able to understand these formats, although it
means that applications have trouble parsing them.
The calculation of job IDs was not described since this would suggest
an implementation, which may impose unnecessary restrictions.
In an early proposal, a
-n
option was included to ``Display the status of jobs that have changed,
exited, or stopped since the last status report''. It was removed
because the shell always writes any changed status of jobs before each
prompt.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.12,
Shell Execution Environment,
bg,
fg,
kill,
wait
The Base Definitions volume of POSIX.1-2008,
Section 3.204,
Job Control Job ID,
Chapter 8,
Environment Variables,
Section 12.2,
Utility Syntax Guidelines
COPYRIGHT
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 during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- OPERANDS
-
- STDIN
-
- INPUT FILES
-
- ENVIRONMENT VARIABLES
-
- ASYNCHRONOUS EVENTS
-
- STDOUT
-
- STDERR
-
- OUTPUT FILES
-
- EXTENDED DESCRIPTION
-
- EXIT STATUS
-
- CONSEQUENCES OF ERRORS
-
- APPLICATION USAGE
-
- EXAMPLES
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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