отображать статус заданий в текущем сеансе (display status of jobs in the current session)
Пролог (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.
Имя (Name)
jobs — display status of jobs in the current session
Синопсис (Synopsis)
jobs [-l|-p] [job_id...]
Описание (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.
Параметры (Options)
The jobs utility shall conform to the Base Definitions volume of
POSIX.1‐2017, 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.
Операнды (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.1‐2017, Section 3.204, Job Control Job ID.
Стандартный ввод (Stdin)
Not used.
Входные файлы (Input files)
None.
Переменные окружения (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.1‐2017, 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.
Асинхронные события (Asynchronous events)
Default.
Стандартный вывод (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 "%%". 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.
Стандартный вывод сообщений (Stderr)
The standard error shall be used only for diagnostic messages.
Выходные файлы (Output files)
None.
Расширенное описание (Extended description)
None.
Статус выхода (Exit)
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Последствия ошибок (Consequences of errors)
Default.
The following sections are informative.
Использование в приложениях (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(1p). For this reason, jobs is generally
implemented as a shell regular built-in.
Примеры (Examples)
None.
Обоснование (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 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.1‐2017 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.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.12, Shell Execution Environment, bg(1p), fg(1p),
kill(1p), wait(1p)
The Base Definitions volume of POSIX.1‐2017, Section 3.204, Job
Control Job ID, Chapter 8, Environment Variables, Section 12.2,
Utility Syntax Guidelines
