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20151204-2 选题
20151204-2 选题
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sources/tech/20151204 Linux or Unix--jobs Command Examples.md
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Linux / Unix: jobs Command Examples
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================================================================================
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I am new Linux and Unix user. How do I show the active jobs on Linux or Unix-like systems using BASH/KSH/TCSH or POSIX based shell? How can I display status of jobs in the current session on Unix/Linux?
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Job control is nothing but the ability to stop/suspend the execution of processes (command) and continue/resume their execution as per your requirements. This is done using your operating system and shell such as bash/ksh or POSIX shell.
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You shell keeps a table of currently executing jobs and can be displayed with jobs command.
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### Purpose ###
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> Displays status of jobs in the current shell session.
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### Syntax ###
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The basic syntax is as follows:
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jobs
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OR
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jobs jobID
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OR
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jobs [options] jobID
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### Starting few jobs for demonstration purpose ###
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Before you start using jobs command, you need to start couple of jobs on your system. Type the following commands to start jobs:
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## Start xeyes, calculator, and gedit text editor ###
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xeyes &
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gnome-calculator &
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gedit fetch-stock-prices.py &
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Finally, run ping command in foreground:
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ping www.cyberciti.biz
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To suspend ping command job hit the **Ctrl-Z** key sequence.
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### jobs command examples ###
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To display the status of jobs in the current shell, enter:
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$ jobs
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Sample outputs:
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[1] 7895 Running gpass &
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[2] 7906 Running gnome-calculator &
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[3]- 7910 Running gedit fetch-stock-prices.py &
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[4]+ 7946 Stopped ping cyberciti.biz
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To display the process ID or jobs for the job whose name begins with "p," enter:
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$ jobs -p %p
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OR
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$ jobs %p
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Sample outputs:
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[4]- Stopped ping cyberciti.biz
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The character % introduces a job specification. In this example, you are using the string whose name begins with suspended command such as %ping.
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### How do I show process IDs in addition to the normal information? ###
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Pass the -l(lowercase L) option to jobs command for more information about each job listed, run:
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$ jobs -l
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Sample outputs:
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Fig.01: Displaying the status of jobs in the shell
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### How do I list only processes that have changed status since the last notification? ###
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First, start a new job as follows:
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$ sleep 100 &
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Now, only show jobs that have stopped or exited since last notified, type:
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$ jobs -n
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Sample outputs:
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[5]- Running sleep 100 &
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### Display lists process IDs (PIDs) only ###
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Pass the -p option to jobs command to display PIDs only:
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$ jobs -p
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Sample outputs:
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7895
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7906
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7910
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7946
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7949
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### How do I display only running jobs? ###
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Pass the -r option to jobs command to display only running jobs only, type:
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$ jobs -r
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Sample outputs:
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[1] Running gpass &
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[2] Running gnome-calculator &
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[3]- Running gedit fetch-stock-prices.py &
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### How do I display only jobs that have stopped? ###
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Pass the -s option to jobs command to display only stopped jobs only, type:
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$ jobs -s
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Sample outputs:
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[4]+ Stopped ping cyberciti.biz
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To resume the ping cyberciti.biz job by entering the following bg command:
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$ bg %4
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### jobs command options ###
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From the [bash(1)][1] command man page:
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注：表格
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<table border="1">
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<tbody>
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<tr>
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<td>Option</td>
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<td>Description</td>
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</tr>
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<tr>
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<td><kbd><strong>-l</strong></kbd></td>
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<td>Show process id's in addition to the normal information.</td>
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</tr>
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<tr>
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<td><kbd><strong>-p</strong></kbd></td>
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<td>Show process id's only.</td>
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</tr>
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<tr>
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<td><kbd><strong>-n</strong></kbd></td>
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<td>Show only processes that have changed status since the last notification are printed.</td>
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</tr>
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<tr>
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<td><kbd><strong>-r</strong></kbd></td>
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<td>Restrict output to running jobs only.</td>
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</tr>
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<tr>
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<td><kbd><strong>-s</strong></kbd></td>
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<td>Restrict output to stopped jobs only.</td>
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</tr>
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<tr>
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<td><kbd><strong>-x</strong></kbd></td>
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<td>COMMAND is run after all job specifications that appear in ARGS have been replaced with the process ID of that job's process group leader./td></td>
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</tr>
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</tbody>
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</table>
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### A note about /usr/bin/jobs and shell builtin ###
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Type the following type command to find out whether jobs is part of shell, external command or both:
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$ type -a jobs
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Sample outputs:
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jobs is a shell builtin
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jobs is /usr/bin/jobs
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In almost all cases you need to use the jobs command that is implemented as a BASH/KSH/POSIX shell built-in. The /usr/bin/jobs command can not be used in the current shell. The /usr/bin/jobs command operates in a different environment and does not share the parent bash/ksh's shells understanding of jobs.
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--------------------------------------------------------------------------------
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via:
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作者：Vivek Gite
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[1]:http://www.manpager.com/linux/man1/bash.1.html
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