Learn the history of Linux commands

This article will bring you information about the history command in Linux

##Article Directory

Preface
• 1. Linux operations on command history
• 1 , Use history to view the history record
  • 2, Use Ctrl r to directly search the execution record
  • 3, Repeat the previous command
  • 4, Execute the command with the corresponding serial number
  5. Modify the total number of lines in the history record
  • 6. Clear the history record
  2. Summary

Preface

Have you ever executed a long command when developing on Linux, and then you need to re-enter it after a while if you want to execute the command?

Everyone must know that in Linux, you can use the ↑ up arrow to find the previously executed command, but if this command takes a long time to execute, it will be very long. Hard to find.

If you are using the xsheel client, it will not be found even if the client is closed.

So how to solve this problem!

##1. Linux operations on command history

1. Use history to view history records

When you execute the history command, the 1000 previously executed commands will be displayed.

But if you don’t log out or shut down, you can save more than 1000 commands. This 1000 is a default value.

Of course, this value can also be modified. If you want to modify it, you can execute the following command.

echo "HISTSIZE=2000" >> .bash_profile 

echo "HISFILETSIZE=2000" >> .bash_profilesource ~/.bash_profile (使其生效即可)

If you are the person in charge of the server and you need to see what command was executed at what point in time, you only need to execute the following command

export HISTTIMEFORMAT="%F %T"

Then you can see the time after executing the history command

## 2. Use Ctrl r to directly search the execution record

For example, if you execute a command to check whether the nginx configuration is correct

usr/local/nginx/sbin/nginx -t

If you want to find a command, just press Ctrl r and then enter usr

3. Repeat the previous command

There are several ways to execute the previous command. The most commonly used one is probably↑This kind of thing.

But what I told Daji today is that you can use !! to operate

## Of course you can also use

!-1 to execute

4. Execute the command corresponding to the serial number

Where does this serial number come from? , which is the command history mentioned first in this article. The serial number of each command will appear after execution.

As shown below, I want to execute the 1020th command, then I can execute it like this !1020.

In fact, anyone with some programming knowledge should be able to understand this command. In the third section, we used !! to execute the previous command, which is actually The last record in history.

同样的道理这个命令使用的是!1020，这样对于这个命令的记忆就有了规律。

5、修改历史记录总行数

在第一节中对于这个总行数的修改也简单的说了一下，但是没有亲自操作，接下来操作一下。

这个命令中HISTSIZE是控制history命令显示的数量

而HISTFILETSIZE控制的是文件中存储的数量

 1039  2021-03-02 22:29:37 echo "HISTSIZE=2000" >> .bash_profile 
 1040  2021-03-02 22:29:58 echo "HISTFILETSIZE=2000" >> .bash_profile 
 1041  2021-03-02 22:30:20 source ~/.bash_profile

Since this command can modify the number of history displays, it can also modify the number of file storage history records.

Just imagine, what if you don’t want the server to record history!

Just change both values ​​to 0.

Can you try it yourself?

#6. Clear the history record

Clear the history record and execute the commandhistory -c

## 2. Summary

View history using history
• Search history using ctrl r
• Repeat the previous command! ! or! -1
• Execute the corresponding serial number command to use! 1020
• HISTSIZE is the number displayed for executing history
• HISTFILETSIZEThe number of historical records saved
• To clear the history, use history -c

The above are about the history commands in Linux, the most commonly used ones are! ! Execute the previous command, and use ctrl r to search for historically executed commands.

Persistence in learning, persistence in blogging, and persistence in sharing are the beliefs that Kaka has always adhered to since its beginning. I hope that Kaka’s articles on the huge Internet can bring you a little bit of help. I’m Kaka, see you next time.

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