diff --git a/sources/tech/20161025 How to Start Linux Command in Background and Detach Process in Terminal.md b/sources/tech/20161025 How to Start Linux Command in Background and Detach Process in Terminal.md new file mode 100644 index 0000000000..a1a8a5b38a --- /dev/null +++ b/sources/tech/20161025 How to Start Linux Command in Background and Detach Process in Terminal.md @@ -0,0 +1,120 @@ +# How to Start Linux Command in Background and Detach Process in Terminal + +In this guide, we shall bring to light a simple yet important concept in [process handling in a Linux system][8], that is how to completely detach a process from its controlling terminal. + +When a process is associated with a terminal, two problems might occur: + +1. your controlling terminal is filled with so much output data and error/diagnostic messages. +2. in the event that the terminal is closed, the process together with its child processes will be terminated. + +To deal with these two issues, you need to totally detach a process from a controlling terminal. Before we actually move to solve the problem, let us briefly cover how to run processes in the background. + +### How to Start a Linux Process or Command in Background + +If a process is already in execution, such as the [tar command example][7] below, simply press `Ctrl+Z` to stop it then enter the command `bg` to continue with its execution in the background as a job. + +You can view all your background jobs by typing `jobs`. However, its stdin, stdout, stderr are still joined to the terminal. + +``` +$ tar -czf home.tar.gz . +$ bg +$ jobs + +``` + +[![Run Linux Command in Background](http://www.tecmint.com/wp-content/uploads/2016/10/Run-Linux-Command-in-Background.png)][6] + +Run Linux Command in Background + +You can as well run a process directly from the background using the ampersand, `&` sign. + +``` +$ tar -czf home.tar.gz . & +$ jobs + +``` + +[![Start Linux Process in Background](http://www.tecmint.com/wp-content/uploads/2016/10/Start-Linux-Process-in-Background.png)][5] + +Start Linux Process in Background + +Take a look at the example below, although the [tar command][4] was started as a background job, an error message was still sent to the terminal meaning the process is still connected to the controlling terminal. + +``` +$ tar -czf home.tar.gz . & +$ jobs + +``` + +[![Linux Process Running in Background Message](http://www.tecmint.com/wp-content/uploads/2016/10/Linux-Process-Running-in-Background-Message.png)][3] + +Linux Process Running in Background Message + +### Keep Linux Processes Running After Exiting Terminal + +We will use disown command, it is used after the a process has been launched and put in the background, it’s work is to remove a shell job from the shell’s active list jobs, therefore you will not use `fg`, `bg` commands on that particular job anymore. + +In addition, when you close the controlling terminal, the job will not hang or send a SIGHUP to any child jobs. + +Let’s take a look at the below example of using diswon bash built-in function. + +``` +$ sudo rsync Templates/* /var/www/html/files/ & +$ jobs +$ disown -h %1 +$ jobs + +``` + +[![Keep Linux Process Running After Closing Terminal](http://www.tecmint.com/wp-content/uploads/2016/10/Keep-Linux-Processes-Running.png)][2] + +Keep Linux Process Running After Closing Terminal + +You can also use `nohup` command, which also enables a process to continue running in the background when a user exits a shell. + +``` +$ nohup tar -czf iso.tar.gz Templates/* & +$ jobs + +``` + +[![Put Linux Process in Background After Closing Shell](http://www.tecmint.com/wp-content/uploads/2016/10/Put-Linux-Process-in-Background.png)][1] + +Put Linux Process in Background After Closing Shell + +### Detach a Linux Processes From Controlling Terminal + +Therefore, to completely detach a process from a controlling terminal, use the command format below, this is more effective for graphical user interface (GUI) applications such as firefox: + +``` +$ firefox /dev/null & + +``` + +In Linux, /dev/null is a special device file which writes-off (gets rid of) all data written to it, in the command above, input is read from, and output is sent to /dev/null. + +As a concluding remark, provided a process is connected to a controlling terminal, as a user, you will see several output lines of the process data as well as error messages on your terminal. Again, when you close the a controlling terminal, your process and child processes will be terminated. + +Importantly, for any questions or remarks on the subject, reach us by using the comment form below. + +-------------------------------------------------------------------------------- + +via: http://www.tecmint.com/run-linux-command-process-in-background-detach-process/# + +作者：[Aaron Kili][a] + +译者：[译者ID](https://github.com/译者ID) + +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: http://www.tecmint.com/author/aaronkili/ +[1]:http://www.tecmint.com/wp-content/uploads/2016/10/Put-Linux-Process-in-Background.png +[2]:http://www.tecmint.com/wp-content/uploads/2016/10/Keep-Linux-Processes-Running.png +[3]:http://www.tecmint.com/wp-content/uploads/2016/10/Linux-Process-Running-in-Background-Message.png +[4]:http://www.tecmint.com/18-tar-command-examples-in-linux/ +[5]:http://www.tecmint.com/wp-content/uploads/2016/10/Start-Linux-Process-in-Background.png +[6]:http://www.tecmint.com/wp-content/uploads/2016/10/Run-Linux-Command-in-Background.png +[7]:http://www.tecmint.com/18-tar-command-examples-in-linux/ +[8]:http://www.tecmint.com/monitor-linux-processes-and-set-process-limits-per-user/