Shulou(Shulou.com)06/01 Report--

This article is about how to carry out the front and background management of Linux tasks. I think it is very practical, so I share it with you. I hope you can get something after reading this article. Let's take a look at it.

We know that Linux is a multitasking operating system, that is, the system can run multiple tasks at the same time. Under the Linux distribution with an interface, we can easily switch multitasking with the mouse. However, under the terminal, the operation is almost separated from the mouse, so how to manage the front and background of the task?

For task management, we generally have the following requirements:

Switch the process to the background

Switch the process to the foreground

View background tasks

Terminate a background task

To demonstrate these requirements, we came up with the great hello world program:

# include

Int main ()

{

While (1) {

Printf ("hello world!\ n")

Sleep (1)

}

}

This program outputs a hello world every 1 second. For the following demonstration, compile and copy multiple samples: hello1, hello2, hello3.

When we let the program run in the background, the first thing we think of is & commands. We can run these three programs in the background first.

[alvin@VM_0_16_centos test] $. / hello1 > test1.txt &

[1] 1788

[alvin@VM_0_16_centos test] $. / hello2 > test2.txt &

[2] 1801

[alvin@VM_0_16_centos test] $. / hello3 > test3.txt &

[3] 1844

Now there are three samples running backstage. How do we view these background tasks? You can use the jobs command.

[alvin@VM_0_16_centos test] $jobs-l

[1] 1788 Running. / hello1 > test1.txt &

[2]-1801 Running. / hello2 > test2.txt &

[3] + 1844 Running. / hello3 > test3.txt &

If we want to set the hello2 to the foreground, we can do this:

[alvin@VM_0_16_centos test] $fg 2

. / hello2 > test2.txt

Where% is followed by a sequence of background tasks, not a process ID. If you only have the fg command (and the bg command is the same) without arguments, you will operate on the first task in the background task list, and the technical term is the current task.

We will find that the program will be stuck in the terminal all the time. At this point, we can use ctrl+z to cut it to the background again.

^ Z

[2] + Stopped. / hello2 > test2.txt

[alvin@VM_0_16_centos test] $jobs-l

[1] 1788 Running. / hello1 > test1.txt &

[2] + 1801 Stopped. / hello2 > test2.txt

[3]-1844 Running. / hello3 > test3.txt &

However, we will find that the test2 process has become the state of stopped, and we can also see its status in the list of background processes. This is also a feature of the ctrl+z command: switch the process to the background and stop running.

If we want to get it running again, we can use the bg command.

[alvin@VM_0_16_centos test] $bg 2

[2] + / hello2 > test2.txt &

[alvin@VM_0_16_centos test] $jobs-l

[1] 1788 Running. / hello1 > test1.txt &

[2]-1801 Running. / hello2 > test2.txt &

[3] + 1844 Running. / hello3 > test3.txt &

If we want to kill a background process, we can use the kill command. The kill command can be used in two ways:

Kill pid

Kill% N

For example, if we want to kill the hello2 process, we can do this:

1. Kill 1801

2. Kill 2

After execution, its state changes to the terminated state:

[alvin@VM_0_16_centos test] $kill 1801

[alvin@VM_0_16_centos test] $jobs-l

[1] 1788 Running. / hello1 > test1.txt &

[2]-1801 Terminated. / hello2 > test2.txt

[3] + 1844 Running. / hello3 > test3.txt &

Foreground and backstage tasks can indeed bring convenience to daily operations. Because, we are sure to encounter multiple operations at the same time in our daily operations. If you don't use foreground and background tasks at this time, it will take a lot of time. Proficient in the use of front and background tasks can achieve twice the result with half the effort.

The above is how to carry out the front and background management of Linux tasks. The editor believes that there are some knowledge points that we may see or use in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.