jobs命令

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命令用途

jobs 命令用于显示当前 Shell 会话中的后台任务列表，包括任务状态（如运行中、已停止、终止等）。

常用用法示例

1. 显示所有后台任务

   jobs 
   [1]-  Running                 sleep 60 &  
   [2]+  Stopped                 vim file.txt  

   输出任务列表，[n] 为任务编号，+ 表示最近任务，- 表示前一个任务，状态为 Running 或 Stopped。

2. 显示任务 ID 及状态（含进程 PID）

   jobs -l  
   [1]-  12345 Running                 sleep 60 &  
   [2]+  12356 Stopped (tty input)     vim file.txt  

   -l 参数显示每个任务的进程 PID（如 12345）和详细状态。

3. 仅显示正在运行的任务

   jobs -r  
   [1]-  Running                 sleep 60 &  

   -r 参数过滤仅显示状态为 Running 的任务。

4. 仅显示已停止的任务

   jobs -s
   [2]+  Stopped                 vim file.txt 

   -s 参数过滤仅显示状态为 Stopped 的任务。

5. 显示任务的最新状态变更

   jobs -n  
   [2]+  Stopped                 vim file.txt  

   -n 参数显示自上次通知后状态发生变化的作业。

6. 仅输出任务 PID（静默模式）

   jobs -p  
   12345  
   12356  

   -p 参数仅输出任务的进程 PID，适用于脚本处理。

7. 显示任务的详细信息（扩展格式）

   jobs -x echo %1  
   12345  

   -x 参数将任务 ID（如 %1）替换为实际 PID，常用于配合其他命令操作。

8. 通过任务 ID 查看特定任务

   jobs %1  
   [1]-  Running                 sleep 60 &  

   直接指定任务 ID（如 %1）查看特定任务的状态。

常用参数选项

• -l, –last
  显示任务的 PID 和完整状态信息。

• -r, –running
  仅显示状态为 Running 的任务。

• -s, –stopped
  仅显示状态为 Stopped 的任务。

• -p, –pid
  仅输出任务的进程 PID，不显示其他信息。

• -n, –newest
  显示最近状态发生变化的作业。

• -x, –command
  将任务 ID 替换为对应的 PID，用于后续命令操作。

• -d, –directory
  显示任务的工作目录（部分 Shell 支持）。

• -h, –help
  显示 jobs 命令的帮助信息（依赖 Shell 实现）。

原厂文档

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.1‐2017, 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.

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.

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.1‐2017, 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.

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 "%%".  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(1p).  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 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.

FUTURE DIRECTIONS

       None.

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

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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 .