JOBS(1P) POSIX Programmer's Manual JOBS(1P)
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 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 Asynchronous Lists .
OPTIONS
The jobs utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, 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 Defini-
tions volume of IEEE Std 1003.1-2001, Section 3.203, 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
IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari-
ables 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 speci-
fied 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>. 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) pro-
vides a way of referring to the process group of the job in an imple-
mentation-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 "%%" and "%+" are used to refer to the current job. Both forms
are of equal validity-the "%%" mirroring "$$" and "%+" mirroring the
output of jobs. Both forms reflect historical practice of the Korn-
Shell 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 IEEE Std 1003.1-2001 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 exam-
ining 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 asso-
ciated 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 vari-
ous 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
Shell Execution Environment, bg, fg, kill(), wait()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 JOBS(1P)
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