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How is the history command used in linux? I believe that many inexperienced people are at a loss about this, so this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

1. Use HISTTIMEFORMAT to display timestamps

When you execute a history command from the command line, it usually only shows the sequence number of the executed command and the command itself. If you want to view the timestamp of the command history, you can execute:

The code is as follows:

# export HISTTIMEFORMAT='%F% T'

# history | more

1 2008-08-05 19:02:39 service network restart

2 2008-08-05 19:02:39 exit

3 2008-08-05 19:02:39 id

4 2008-08-05 19:02:39 cat / etc/redhat-release

Note: this function can only be used when the environment variable HISTTIMEFORMAT is set, and then those newly executed bash commands will be stamped correctly. All commands prior to this will be displayed as the time to set the HISTTIMEFORMAT variable.

two。 Use Ctrl+R to search for history

Ctrl+R is one of the keyboard shortcuts I often use. This shortcut allows you to search the command history and is useful when you want to repeat a command. When a command is found, you can usually press enter to execute the command. If you want to adjust the command you find before executing it, you can press the left or right arrow keys.

The code is as follows:

# [Press Ctrl+R from the command prompt, which will display the reverse-i-search prompt]

(reverse-i-search) `red': cat / etc/redhat-release

[Note: Press enter when you see your command, which will execute the command from the history]

# cat / etc/redhat-release

Fedora release 9 (Sulphur)

3. Quickly repeat the previous command

There are four ways to repeat the previous command:

Use the up arrow keys and press enter to execute.

Press! And enter to execute.

Enter!-1 and enter to execute.

Press Ctrl+P and press enter to execute.

4. Execute a specified command from the command history

In the following example, if you want to repeat the fourth command, you can do it! 4:

The code is as follows:

# history | more

1 service network restart

2 exit

3 id

4 cat / etc/redhat-release

#! 4

Cat / etc/redhat-release

Fedora release 9 (Sulphur)

5. Execute previous commands by specifying keywords

In the following example, enter! ps and enter, and the command that starts with ps will be executed:

The code is as follows:

#! ps

Ps aux | grep yp

Root 16947 0.0 0.1 36516 1264? Sl 13:10 0:00 ypbind

Root 17503 0.0 4124 740 pts/0 S + 19:19 0:00 grep yp

6. Use HISTSIZE to control the total number of rows recorded by the history command

Append the following two lines to the .bash _ profile file and log in to bash shell again, and the number of records of command history will be 450:

The code is as follows:

# vi ~ / .bash_profile

HISTSIZE=450

HISTFILESIZE=450

7. Change the history file name using HISTFILE

By default, the command history is stored in the ~ / .bash_history file. Add the following to the .bash _ profile file and log in to bash shell again, using .commandline _ warrior to store the command history:

The code is as follows:

# vi ~ / .bash_profile

HISTFILE=/root/.commandline_warrior

8. Use HISTCONTROL to remove consecutive repeated entries from the command history

In the following example, the pwd command is executed three times in a row. After executing history, you will see three duplicate entries. To remove these duplicates, you can set HISTCONTROL to ignoredups:

The code is as follows:

# pwd

# pwd

# pwd

# history | tail-4

44 pwd

45 pwd

46 pwd [Note that there are three pwd commands in history, after executing pwd 3 times as shown above]

47 history | tail-4

# export HISTCONTROL=ignoredups

# pwd

# pwd

# pwd

# history | tail-3

56 export HISTCONTROL=ignoredups

57 pwd [Note that there is only one pwd command in the history, even after executing pwd 3 times as shown above]

58 history | tail-4

9. Use HISTCONTROL to clear duplicate entries throughout the command history

The ignoredups in the above example can only eliminate consecutive duplicate entries. To clear duplicate entries throughout the command history, set HISTCONTROL to erasedups:

The code is as follows:

# export HISTCONTROL=erasedups

# pwd

# service httpd stop

# history | tail-3

38 pwd

39 service httpd stop

40 history | tail-3

# ls-ltr

# service httpd stop

# history | tail-6

35 export HISTCONTROL=erasedups

36 pwd

37 history | tail-3

38 ls-ltr

39 service httpd stop

[Note that the previous service httpd stop after pwd got erased]

40 history | tail-6

10. Use HISTCONTROL to force history not to remember specific commands

Set HISTCONTROL to ignorespace and enter a space before the command you don't want to remember:

The code is as follows:

# export HISTCONTROL=ignorespace

# ls-ltr

# pwd

# service httpd stop [Note that there is a space at the beginning of service, to ignore this command from history]

# history | tail-3

67 ls-ltr

68 pwd

69 history | tail-3

11. Use the-c option to clear all command history

If you want to erase all command history, you can execute:

The code is as follows:

# history-c

twelve。 Command replacement

In the following example,!: $will get the parameters of the previous command for the current command:

The code is as follows:

# ls anaconda-ks.cfg

Anaconda-ks.cfg

# vi!: $

Vi anaconda-ks.cfg

Add: use! $can achieve the same effect, and easier.

In the following example,! ^ gets the first parameter from the previous command:

The code is as follows:

# cp anaconda-ks.cfg anaconda-ks.cfg.bak

Anaconda-ks.cfg

# vi-5! ^

Vi anaconda-ks.cfg

13. Replace the specified parameters for a specific command

In the following example,! cp:2 searches the command history for a command that starts with cp and gets its second argument:

The code is as follows:

# cp ~ / longname.txt / really/a/very/long/path/long-filename.txt

# ls-l! cp:2

Ls-l / really/a/very/long/path/long-filename.txt

In the following example,! cp:$ gets the last argument of the cp command:

The code is as follows:

# ls-l! cp:$

Ls-l / really/a/very/long/path/long-filename.txt

14. Disable history using HISTSIZE

If you want to disable history, you can set HISTSIZE to 0:

The code is as follows:

# export HISTSIZE=0

# history

# [Note that history did not display anything]

15. Use HISTIGNORE to ignore specific commands in history

The following example ignores commands such as pwd, ls, ls-ltr, and so on:

The code is as follows:

# export HISTIGNORE= "pwd:ls:ls-ltr:"

# pwd

# ls

# ls-ltr

# service httpd stop

# history | tail-3

79 export HISTIGNORE= "pwd:ls:ls-ltr:"

80 service httpd stop

81 history

[Note that history did not record pwd, ls and ls-ltr]

After reading the above, have you mastered how the history command is used in linux? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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