Clear Linux / UNIX BASH Shell Command Line Cache / History

To display the history list with line numbers, enter

$ history
Output:

....
..
  4  cd /tmp/
    5  wget http://downloads.wordpress.org/plugin/cleaner-dashboard.1.1.zip
    6  unzip cleaner-dashboard.1.1.zip 
    7  su - 
    8  vi /etc/httpd/testing.lan.cyberciti.biz.conf
    9  service httpd restart
.....
..
 997  vnstat -m -i eth1
  998  date
  999  yum update
 1000  w
 1001  ~/scripts/clean.cache rss squid web
 1002  history

To see last 10 commands from history, run:
$ history 10
Sample outputs:

 1998  df -H
 1999  dmesg 
 2000  cbz_wp_admin on 
 2001  cbz_wp_admin off
 2002  file_replication --check --status
 2003  ~/bin/purge.cache --key=XXXXXX
 2004  echo $HISTFILE
 2005  echo $HISTFILE 
 2006  cbz_wp_admin --uploads on
 2007  history 10

You can search for the lines that have ‘cf.purge.sh’ in history by typing the following grep command:
$ history | grep "commmand-to-search"
$ history | grep "cf.purge.sh'
Another option is to type CTRL+r for searching searching backwards in history.

How to run commands from my bash history

Now you know how to display history list along with line numbers. To execute command # 2002 ( file_replication --check --status), run:
$ !2002
I just recalled previous history command by its number preceded by an exclamation point. To call previous command, type:
$ !!
For example, the following will fail as I forget to add sudo:
$ systemctl restart httpd
Just enter sudo !! and command will re-execute with sudo in front of it:
$ sudo !!

How to scroll through bash history

Simply press UP or DOWN arrow key to Scroll backwards and forwards in history respectively.

How to clear the history, enter:

$ history -c
To delete the history entry at offset i.e. command number 100 from history file:
$ history -d 100
The -c option causes the history list to be cleared by deleting all of the entries. For more information, enter:
$ help history
Sample outputs:

      -c	clear the history list by deleting all of the entries
      -d offset	delete the history entry at offset OFFSET.
 
      -a	append history lines from this session to the history file
      -n	read all history lines not already read from the history file
      -r	read the history file and append the contents to the history
    	list
      -w	write the current history to the history file
    	and append them to the history list
 
      -p	perform history expansion on each ARG and display the result
    	without storing it in the history list
      -s	append the ARGs to the history list as a single entry

Explains how to use history bash command to get a history of all commands with date and time listed as well.