Delete the History of the Last n Commands on Linux

In Linux, the command history is a record of previously executed commands stored in a file called .bash_history, located in each user's home directory. The history command displays this history, and commands are assigned sequential numbers that can be executed using !number syntax. For example, typing !123 will execute the command numbered 123 in the history.

There are several options to customize command history behavior:

• The history -c command clears the current session's command history.

• The HISTFILE environment variable specifies a different file to store command history.

• The HISTSIZE and HISTFILESIZE variables control the maximum number of commands stored in memory and in the history file, respectively.

• The HISTIGNORE variable excludes specific commands or patterns from being recorded.

• The set -o history command enables command history for shells that have it disabled.

Difference Between history Command and .bash_history File

The history command is a built-in Bash command that displays commands from the current shell session, showing the most recent commands first. Each command has a number that can be used for quick execution with the ! prefix.

The .bash_history file is a plain text file storing the persistent command history for a specific user. It's updated when the shell session ends and can be viewed with any text editor. Commands from this file are loaded into memory when a new shell session starts.

Delete Last n Commands from .bash_history File

To delete the last n commands from the .bash_history file, you can use the sed command. Here are the most effective methods:

Method 1: Using head and mv

# Delete last 5 commands from .bash_history
head -n -5 ~/.bash_history > ~/.bash_history.tmp && mv ~/.bash_history.tmp ~/.bash_history

Method 2: Using sed

# Delete last n lines (replace 5 with desired number)
sed -i '$d' ~/.bash_history  # Delete last line
sed -i -e :a -e '$d;N;2,5ba' -e 'P;D' ~/.bash_history  # Delete last 5 lines

Method 3: Using tail and sponge

# Install moreutils first: sudo apt install moreutils
head -n -5 ~/.bash_history | sponge ~/.bash_history

Warning: These commands modify the .bash_history file directly and changes are irreversible. Always backup the file before making modifications:

cp ~/.bash_history ~/.bash_history.backup

Delete Last n Commands from Current Session

To delete commands from the current shell session's history without affecting the .bash_history file:

Delete Specific Range

# Delete commands 100 to 105
history -d 100-105

Delete Last n Commands

# Delete last 3 commands
for i in {1..3}; do history -d -1; done

Alternative Method

# Get current history size and delete last 5 commands
LAST=$(history | tail -1 | awk '{print $1}')
history -d $((LAST-4))-$LAST

These changes only affect the current session and won't persist to the .bash_history file unless you run history -w.

Advanced History Management

Modern Bash versions (5.0+) provide enhanced history features:

• Timestamps Enable with HISTTIMEFORMAT="%Y-%m-%d %H:%M:%S "

• History appending Use shopt -s histappend to append rather than overwrite

• Real-time updates Set PROMPT_COMMAND="history -a" for immediate saves

• Unlimited history Set HISTSIZE=-1 and HISTFILESIZE=-1

Practical Examples

Remove Sensitive Commands

# Remove last command containing password
history -d $(history | grep "password" | tail -1 | awk '{print $1}')

Clean Up Before Logging Out

# Remove last 10 commands and save history
for i in {1..10}; do history -d -1; done
history -w

Conclusion

Managing command history in Linux provides control over what commands are stored and accessible. You can delete specific commands from both the current session using history -d and from the persistent .bash_history file using tools like sed or head. Always backup your history file before making bulk changes, as these operations are irreversible.