Q. How do I search old command history under bash shell? How do I display or modify previous commands?

A. Almost all modern shell allows you to search command history if enabled by user. Use history command to display the history list with line numbers. Lines listed with with a * have been modified by user.

Shell history search command

Type history at a shell prompt:
$ history
Output:
Sample output:

  6  du -c
    7  du -ch
    8  ls [01-15]*-2008
    9  ls -ld [01-15]*-2008
   10  ls -ld [1-15]*-2008
   11  ls -ld [0]*-2008
   12  ls -ld [01]*-2008
   13  rm -vrf [01]*-2008
   14  du -ch
   15  ls
   16  cd
   17  umount /mnt
   18  df -H
   19  vnstat
   20  yum update
   21  vnstat -m
   22  vnstat -m -i eth0
....
...
  996  ping router.nixcraft.in
  997  ssh vivek@p1.vpn.nixcraft.in
  998  alias 
  999  ~/scripts/clean.rss --fetch
 1000  vnstat
 1001  ~/scripts/clean.rss  --update

To search particular command, enter:
$ history | grep command-name
$ history | egrep -i 'scp|ssh|ftp'


Emacs Line-Edit Mode Command History Searching

To get previous command containing string, hit [CTRL]+[r] followed by search string:

(reverse-i-search): 

To get previous command, hit [CTRL]+[p]. You can also use up arrow key.

CTRL-p

To get next command, hit [CTRL]+[n]. You can also use down arrow key.

CTRL-n

fc command

fc stands for either “find command” or “fix command. For example list last 10 command, enter:
$ fc -l 10
To list commands 130 through 150, enter:
$ fc -l 130 150
To list all commands since the last command beginning with ssh, enter:
$ fc -l ssh
You can edit commands 1 through 5 using vi text editor, enter:
$ fc -e vi 1 5

Delete command history

The -c option causes the history list to be cleared by deleting all of the entries:
$ history -c