HISTORY usage Summary

The usage of HISTORY summarizes the usage of HISTORY. I. Use HISTTIMEFORMAT to display the timestamp. After you execute the history command from the command line, only the serial number of the executed command and the command itself are displayed. To view the timestamp of the command history, run the following command: # 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 2. use Ctrl + R search history Ctrl + R is a frequently used shortcut key. This shortcut allows you to search for command history, which is useful when you want to execute a command repeatedly. After finding the command, you can usually press the Enter key to execute the command. If you want to adjust the command and then execute it, you can click the left or right arrow keys. # [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. You can repeat the previous command in four ways: use the up arrow key and press enter to execute. Press !! And press enter to execute. Enter! -1 and press enter to execute. Press Ctrl + P and press Enter. 4. Execute a specified command from the command history. In the following example, if you want to repeat 4th commands, You can execute them! 4: # 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. Run the previous command by specifying the keyword. In the example below, enter! Ps and press Enter. The command with ps headers will be executed :#! Ps aux | grep yp root 16947 0.0 0.1 36516 1264? Sl ypbind root 17503 0.0 0.0 4124 740 pts/0 S + grep yp 6. Use HISTSIZE to control the total number of rows recorded in the history command to append the following two rows. bash_profile file and log on to bash shell again. The number of command history records will change to 450: # vi ~ /. Bash_profile HISTSIZE = 450 HISTFILESIZE = 450 7. Use HISTFILE to change the name of a historical file. By default, the command history is stored in ~ /. Bash_history file. Add the following content to the. bash_profile file and log on to the bash shell again. The. commandline_warrior command history will be stored: # vi ~ /. Bash_profile HISTFILE =/root/. commandline_warrior 8. Use HISTCONTROL to remove consecutive duplicate entries from the command history. In the following example, the pwd command is executed three times in a row. After history is executed, you will see three duplicate entries. To remove these duplicate entries, you can set HISTCONTROL to ignoredups: # 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 # history | tail-3 56 export HISTCONTROL = ignoredups 57 pwd [note that there is only one pwd command in the history, even after exe Cuting pwd 3 times as shown above] 58 history | tail-4 9. Use HISTCONTROL to clear duplicate entries in the history of the entire command. In the previous example, ignoredups can only remove consecutive duplicate entries. To clear duplicate entries in the history of the entire command, you can set HISTCONTROL to erasedups: # 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 to set HISTCONTROL to ignorespace, enter a space before the command that you do not want to remember: # 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 use the-c option to clear all command history 11 if you want to clear history of all commands, run the following command: # history-c 12. Use HISTSIZE to disable history. If you want to disable history, set HISTSIZE to 0: # export HISTSIZE = 0 # history # [Note that history did not display anything] 13. Use HISTIGNORE to ignore specific commands in history, commands such as pwd, ls, and ls-ltr will be ignored: # export HISTIGNORE = "pwd: ls-ltr: "# pwd # ls-ltr # service httpd stop # history | tail-3 79 export HISTIGNORE =" pwd: ls-ltr: "80 service httpd stop 81 history [Note that history did not record pwd, ls and ls-ltr]