Using the command history---取回以前曾經鍵入過的命令

來源:

http://wiki.linux.org.hk/w/Recall_the_previous_entered_command

http://linux.about.com/od/lts_guide/a/gdelts16.htm

GNU/Linux Command-Line Tools Summary

   Prev    Chapter 4. Shell Tips    Next

4.2. The command-line history

• Using the command history
   
Use the up and down key's to scroll through previously typed commands. Press [Enter] to execute them or use the left and right arrow keys to edit the command first. Also see history(below).
• The history command
   
The history command can be used to list Bash's log of the commands you have typed:
This log is called the “history”. To access it type:
   

history n

This will only list the last n commands. Type “history” (without options) to see the the entire history list.
You can also type !n to execute command number n. Use !! to execute the last command you typed.
!-n will execute the command n times before (in other words !-1 is equivalent to !! ).
!string will execute the last command starting with that “string” and !?string? will execute the last command containing the word “string”. For example:
   

!cd

Will re-run the command that you last typed starting with “cd”.
“ commandName !*” will execute the “commandName” with any arguments you used on your last command. This maybe useful if you make a spelling mistake, for example. If you typed:
   

emasc /home/fred/mywork.java /tmp/testme.java

In an attempt to execute emacs on the above two files this will obviously fail. So what you can do is type:
   

emacs !*

This will execute emacs with the arguments that you last typed on the command-line. In other words this is equivalent to typing:
   

emacs /home/fred/mywork.java /tmp/testme.java

• Searching through the Command History ( CTRL -R )
   
Use the CTRL-R key to perform a “reverse-i-search”. For example, if you wanted to use the command you used the last time you used snort , you would type:
CTRL -R then type “snort”.
What you will see in the console window is:
   

(reverse-i-search)'':

After you have typed what you are looking for, use the CTRL -R key combination to scroll backward through the history.
Use CTRL -R repeatedly to find every reference to the string you've entered. Once you've found the command you're looking for, use [Enter] to execute it.
Alternatively, using the right or left arrow keys will place the command on an actual command-line so you can edit it. -----------------------------------------------------------------------------------------

取回以前曾經鍵入過的命令

目錄  [隱藏] 1 history 2 !n 3 !-n 4 !! 5 !? 6 上下箭咀鍵 7 Ctrl-R 8 Bash命令紀錄設定

history

很多 shell 都會把您曾經鍵入過的命令記錄在記憶體中，您可以用指令 history 列出來：

$ history
  1  ls
  2  mount /media/sd_mmc
  3  ls /media/sd_mmc
  4  cd ..
  5  dir
  6  dcim/
  7  ls
  8  vdir
  9  cd ..
 10  cd Images/
 11  ls
 12  cd ..
 13  cd
 14  umount /media/sd_mmc/
 15  cd
 16  ls -lhSr
 17  rm core
 18  df -h
 19  cd photo
 20  ls

以上列表中，左邊為命令編數，右邊為命令本身。您每鍵入一個命令，Shell 都會記下來並指定命令編數為上一個命令加一。

 !n

您可以打「!命令編數」直接執行。例如您打「!16」，Shell 就會直接執行編號第 16 的命令「ls -lhSr」。

 !-n

如果命令編數為負數，表示要執行對上幾次的命令。例如您打「!-3」，Shell 就會直接執行倒數第三個命令(即編號第 18 的命令)「df -h」。

 !!

打「!!」等於「!-1」，表示執行倒數第一個命令(即編號第 20 的命令)「ls」。

 !?

打「!?關鍵字」會執行對上一個包括關鍵字的命令。例如「!?mmc」，Shell 會找最後一次包括「mmc」的命令，即是編數第 14 的命令「umount /media/sd_mmc/」。

上下箭咀鍵

現時有部份 shell 包括 bash(一般 GNU/Linux 預設)、tcsh 和 zsh 等都可以用上下箭咀鍵取回以前曾經鍵入過的命令。

Ctrl-R

按 Ctrl-R 打鍵入關鍵字，shell會尋找上一次包括關鍵字的命令。例如按 Ctrl-R 打鍵入「m」，Shell會顯最後一個包含「m」的命令：「rm core」。

再鍵入「m」，Shell 會顯示最後一個包含「mm」的命令：「umount /media/sd_mmc/」。

再按一次 Ctrl-R，shell 會顯示對上次包含相同關鍵字「mm」的命令：「ls /media/sd_mmc/」。再按一次 Ctrl-R，會顯示再對上次包含相同關鍵字「mm」的命令：「mount /media/sd_mmc/」。

Bash命令紀錄設定

環境變數 HISTSIZE 可以用來設定 bash 最多會記錄命令的數目，例如：

export HISTSIZE=5000

您登出 (logout) 或正常離開 bash 時會將記憶體命令紀錄儲存在環境變數 HISTFILE 所指定的檔案 (預值為 ~/.bash_history) 中。再您下次再執行 bash 或開啟終端機Terminal時就會自動載入以前曾經鍵入過的命令。您亦可以改環境變數 HISTFILESIZE 設定 .bash_history 儲存命令數目，例如：

export HISTFILESIZE=5000

*****留意您登出或離開 bash 後，所有環境變數變回預設值, 您要將以上那幾行 export 加入 ~/.bash_profile 才會永久生效。