📘 Mastering the Terminal: The Bash History

Understanding and efficiently using Bash history helps speed up workflow, avoid retyping, and even prevent mistakes.

Two environment variables control its behavior:

Variable	Description	Example
`HISTFILESIZE`	Max number of commands in the `.bash_history` file	`echo $HISTFILESIZE` → `2000`
`HISTSIZE`	Max number of commands kept in memory (used by `history` command)	`echo $HISTSIZE` → `1000`

⚠️ .bash_history is only updated after logout.

history            # Show recent commands (from memory, not full file)
cat ~/.bash_history  # Show saved command history from the file

Syntax	Action
`!number`	Run the command by its history number (e.g., `!17`)
`!!`	Run the last command
`!-n`	Run the command that was `n` commands ago (e.g., `!-3`)
`!command`	Run the most recent command that starts with `command` (e.g., `!ping`)
`!command:p`	Print the matched command without executing it

Shortcut	Action
`↑` / `Ctrl + P`	Previous command
`↓` / `Ctrl + N`	Next command
`Ctrl + R`	Reverse search in history (interactive)
`Ctrl + G`	Exit reverse search without executing
`Ctrl + P` in reverse search	Run the found command

✅ Example:

Ctrl + R → type 'ping' → press Enter → runs last 'ping' command
Ctrl + R → type 'cat' → Ctrl + G → exits search mode

Command	Action
`history -d <number>`	Delete a specific command by its number
`history -c`	Clear the entire session history