In Linux, if you use a terminal operating system (sh, bash, zsh, fish, etc.), then there is a very powerful and convenient command calledhistory. Its purpose is to allow you to view all the command records entered in the terminal before, and to easily and quickly execute a command or modify some parameters before re-executing it. Let's take a look at the commonly used commands for Linux history:
1. Linux history view all historical command lists
When using a terminal, we often enter very long commands, but sometimes we need to execute similar commands again, which can be used in bash or zsh terminalshistoryCommand to view the commands entered before. Enter the following command in the terminal to view the historical command list:
history
This command can display the last 500 command records previously entered into the terminal. Each command has a corresponding number, and the number starts from 1.
2. View the history of specific Linux commands
If you need to view the history of a specific command, you can usehistoryUse a combination of commands and grep commands, for example:
history | grep "ls"
This command will output all the command records containing "ls" that have been entered before, includingls、 ls -landls /etcWait for the order.
3. UsehistoryRepeat the command
When executing commands in a terminal, we may need to execute commands that have been used several times. and usehistoryCommands can be easily found and executed repeatedly.
For example, if you want to execute a command numbered 42 again, you can use the following command:
!42
In addition, you can also use exclamation marks (!) commands in the quick operation history, such as:
-
!!Repeat the previous command -
!-2Repeat the penultimate command -
!nRepeat the nth command, e.g.!3Indicates repeated execution of the third command -
!stringRepeat the most recent command starting with string
4. ControlhistoryNumber of records
By default,historyThe command will record the 1,000 most recently entered commands, but if the number of commands entered is very large, this number may not meet the requirements, so it can be setHISTSIZEVariables to expand or shrinkhistoryNumber of records.
For example, the following command willhistoryThe number of records is limited to 2000:
export HISTSIZE=2000
5. Linux history display time
In addition to the command number and command content,historyYou can also record the timestamp of each command. If you need to view the execution time of the command, you can use the following command:
export HISTTIMEFORMAT="%F %T "
This command willhistoryThe date and timestamp of each command execution is displayed when output.
6、Linux clear history
ClearhistoryRecord, whenhistoryWhen records become huge, we may need to clear all history to save hard disk space or data privacy and security considerations. You can use the following command to clear the history:
history -c
This command will completely clear allhistoryRecord.
7. Linux history file location
In Linux systems,historyThe historical commands recorded by the command are saved in a file. This file is usually called a "history file" and is located in the user's home directory.
For most common Linux distributions, the default location of history files is~/.bash_history. in~Represents the user's home directory,.bash_historyIt is a hidden file, can be usedls -aThe command displays hidden files.
Take Bash as an example. After you enter a command in the terminal, the command record will be appended to the history file. Every time a new terminal session is opened,historyThe command reads the file and displays the history on the terminal.
You can use a text editor to open the history file for viewing or editing, for example:
vi ~/.bash_history
Or you can use it directlycatCommand to view its contents:
cat ~/.bash_history
It should be noted that the history file may contain only the most recent part of the commands, because its size is limited by the number of history records.
It is worth mentioning that different shells may use different historical files, such as Zsh~/.zsh_history, Fish~/.config/fish/fish_history. However, in most common Linux distributions, Bash is used by default, and the corresponding historical files are~/.bash_history。
For more details, please refer to:
Detailed explanation of the usage of history commands under Linux