In-depth analysis of the similarities and differences between nohup and &

In-depth analysis of the similarities and differences between nohup and &

In Linux systems, we often use the nohup command and the ampersand to run programs in the background to avoid the program being closed when the terminal is closed. Then close. Although they can both implement the function of running a program in the background, there are some differences between nohup and &. This article will provide an in-depth analysis of the similarities and differences between nohup and & to help readers better understand and use them correctly.

1. nohup command

1. Introduction

nohup is the abbreviation of "no hang up", its function It runs the command without hanging up. Even if the current terminal is closed, it will not affect the running of the program. Through the nohup command, we can run the program in the background to avoid program interruption due to the closing of the terminal.

2. How to use

To use the nohup command, just add nohup before the command. For example:

nohup command &

This will allow the command to run in the background and will not be affected by closing the terminal.

3. Features

• The nohup command will redirect the standard output and error output to a file named nohup.out, which means that if If the program has output, it will be saved in nohup.out instead of displayed in the terminal.
• When you use the nohup command to run a program, a subshell will be started in the background to execute the command.

2. & symbol

1. Introduction

In the Linux system, the ampersand symbol can convert commands Run in the background. Similar to nohup, using the & symbol prevents the program from being terminated when the terminal is closed. However, the & symbol does not have the additional features of the nohup command, such as redirecting output.

2. How to use

To use the & symbol, just add & at the end of the command. For example:

command &

This will make the command run in the background and be disconnected from the current terminal.

3. Features

• After using the & symbol, the output of the command will be displayed directly in the terminal and will not be redirected to other files.
• When using the & symbol, you can use Ctrl Z to suspend the command and use the bg command to move it to the background.

3. Comparison of similarities and differences

1. Output processing:

   • nohup The command will redirect the output to the nohup.out file, and the & symbol will display the output directly in the terminal.

2. Program running environment:

   • The nohup command will start a subshell in the background to execute the command, and the & symbol Put the command to run in the background directly in the current shell.

3. Function limitations:

   • nohup can handle problems after the terminal is closed, and can also redirect output; The & symbol can only put the command to run in the background, and the output is displayed directly in the terminal.

in conclusion

In general, the nohup command and the & symbol can realize the function of placing the command in the background to avoid the program being terminated when the terminal is closed. Using the nohup command can better handle program output and terminal closing issues, and has a certain output redirection function; while the & symbol is simpler and more direct, suitable for simple background running needs.

In actual applications, choosing the appropriate way to run programs in the background according to different needs will be more conducive to improving efficiency and management. I hope this article will help readers understand the similarities and differences between the nohup command and the & symbol.

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