Linux Bash Scripting: How to ignore specific commands from being stored in the history in Linux

If you see the history of your commands using the "history" command, you can see all the commands that you executed in the command line. If you don't want certain basic commands to be stored in your history, you can ignore them using HISTIGNORE. You can specify all the commands that you want to ignore in the HISTIGNORE. 

In the below code, I have ignored the commands pwd, ls, ls -ltr and l using HISTIGNORE. Then I am executing some commands in the command line. Finally I'm checking the output of the history command.

$ export HISTIGNORE="pwd:ls:ls -ltr:l:" $ ls $ l $ ls -ltr $ pwd $ cd $HOME $ history | tail -3 379 export HISTIGNORE="pwd:ls:ls -ltr:l:" 380 cd $HOME 381 history
[Note that history did not record ls, l, ls -ltr and pwd]

Please note that adding ls does not exclude the command ls -al from being included in the history. So, you need to specify the complete command to make it as an exception.

Linux bash scripting: How to repeat the previous command quickly in the Linux command line

There are four different ways by which we can repeat the previous commands that we executed in the command line.

1) use the "UP arrow" to view the previous command and press Enter to execute it.
2) Type !! and press enter from the command line
3) Type !-1 and press enter from the command line.
4) Press Control+P to display the previous commands. You can keep pressing the Ctrl+P to older commands. When you see the required command you can press enter to execute it

Linux bash scripting: How to search the command history (previously executed commands)

We often need to type long commands in the command line which we typed earlier. Instead of typing it again we can search the command history for the command we executed and execute it again. This technique will come handy when you are required to type a long command that you executed previously.

To search the command history and execute the command without editing it, Press Ctrl+R and type the keyword present in the previously executed command.

In the below example, I searched for the word "work", which displayed the previous command "cd /home/sittik/test/DDI/work" in the history that contained the word work.

$ [Press Ctrl+R from the command prompt, which will display the reverse-i-search prompt] (reverse-i-search)`work': cat /home/sittik/test/DDI/work [Note: Press enter when you see your command, which will execute the command from the history] $ cat /home/sittik/test/DDI/work This is my work data

Suppose if you need to edit the command before executing it, you can use the left or right arrow key without pressing enter. For example, you can search for "httpd" and which will display the command "service httpd stop" from the command history. You can change this command to "service httpd start" and execute it as shown below.

$ [Press Ctrl+R from the command prompt, which will display the reverse-i-search prompt] (reverse-i-search)`httpd': service httpd stop [Note: Press either left arrow or right arrow key when you see your command, which will display the command for you to edit, before executing it] $ service httpd start

linux Bash Scripting: how to display the history of commands along with the timestamp

Usually the history command will display the command number and the command when you execute the command from the command line. Suppose if you want to add the timestamp along with the command history for auditing purpose, you can do it using the HISTTIMEFORMAT as shown below.

$ export HISTTIMEFORMAT='%F %T ' $ history | less 1 2012-10-11 04:12:36 vi .profile 2 2012-10-11 04:12:36 ls -al 3 2012-10-11 04:12:36 vi .bash_profile 4 2012-10-11 04:12:36 source ./.bash_profile