Linux — Command History and Shortcuts

5 minute read

Linux keeps a record of every command you type. Knowing how to search and reuse this history — combined with keyboard shortcuts — dramatically speeds up your work.

history — View Past Commands

# Show all recent commands with line numbers
history
# 1  ls -la
# 2  cd /var/log
# 3  tail -f syslog
# 4  cd ~
# 5  sudo apt update

# Show last N commands
history 20

# Show history with timestamps (if HISTTIMEFORMAT is set)
HISTTIMEFORMAT="%Y-%m-%d %H:%M  "
history
# 1  2025-04-01 09:00  ls -la
# 2  2025-04-01 09:05  cd /var/log

# Make timestamps permanent
echo 'export HISTTIMEFORMAT="%Y-%m-%d %H:%M  "' >> ~/.bashrc

# Search history with grep
history | grep "docker"
# 23  docker ps -a
# 47  docker build -t myapp .
# 89  docker-compose up -d

# Clear history
history -c           # Clear in-memory history
history -w           # Write (current) history to file
> ~/.bash_history    # Wipe the history file (careful!)

History Expansion: Reusing Commands

!! — Last Command

# Repeat the last command exactly
ls -la /etc/nginx
!!
# ls -la /etc/nginx  (executed again)

# Most common use: forgot sudo
apt update
# E: Could not open lock file /var/lib/dpkg/lock-frontend (Permission denied)

sudo !!
# sudo apt update   ← automatically expanded
# [sudo] password for ubuntu: ••••

!n — Command by Number

# Re-run command number 47 from history
!47
# docker build -t myapp .   (whatever command 47 was)

# Verify what command 47 is before running
history | grep "^  47"
# 47  docker build -t myapp .

!string — Last Command Starting With

# Re-run the most recent command starting with "docker"
!docker
# docker-compose up -d   ← last docker command

# Re-run the most recent command starting with "ssh"
!ssh
# ssh ubuntu@54.123.45.67

# Expand without executing (check first)
!docker:p
# docker-compose up -d   ← printed, NOT run

!$ — Last Argument of Previous Command

# mkdir a directory and immediately cd into it
mkdir -p /tmp/newproject/src
cd !$
# cd /tmp/newproject/src

# Create a file then open it in vim
touch /etc/nginx/conf.d/myapp.conf
vim !$
# vim /etc/nginx/conf.d/myapp.conf

Ctrl+R — Reverse Incremental Search

This is the most powerful history feature — search through history as you type:

# Press Ctrl+R and start typing
(reverse-i-search)`':
(reverse-i-search)`do': docker-compose up -d

# Ctrl+R again → go to the previous match
# Enter → run the found command
# → (right arrow) → edit the command before running
# Ctrl+G or Ctrl+C → cancel the search

# Example workflow:
# You want to re-run a long docker command from earlier

1. Press Ctrl+R
   (reverse-i-search)`:
   
2. Type "docker build"
   (reverse-i-search)`docker build': docker build -t myapp:latest --build-arg ENV=prod .
   
3. Press Enter to run it
   OR press → to copy it to the command line for editing

Readline Keyboard Shortcuts

These shortcuts work in bash (and most Linux terminals):

Cursor Movement

Shortcut Action
Ctrl+A Jump to beginning of line
Ctrl+E Jump to end of line
Alt+F Move forward one word
Alt+B Move backward one word
Ctrl+F Move forward one character
Ctrl+B Move backward one character

Editing

Shortcut Action
Ctrl+K Delete from cursor to end of line
Ctrl+U Delete from cursor to beginning of line
Ctrl+W Delete the word before the cursor
Alt+D Delete the word after the cursor
Ctrl+Y Paste (yank) previously killed text
Ctrl+_ Undo last change

Process Control

Shortcut Action
Ctrl+C Kill current command
Ctrl+Z Suspend current process to background
Ctrl+D Send EOF / logout of current shell
Ctrl+L Clear the screen (same as clear)

Practical Shortcuts

# Long command — move to beginning to fix a typo
sudo apt install python3-pip python3-dev python3-venv libssl-dev
# Cursor is at end — press Ctrl+A to jump to start
# Press Alt+F to move forward word by word
# Press Ctrl+W to delete the word before cursor

# Fix a typo in a URL without retyping
curl -X POST https://api.example.com/v1/users -H "Content-Type: application/json"
# Typo in URL — press Ctrl+A then Alt+F to navigate to it
# Or press Ctrl+R and search for the unique part

# Clear the screen without losing the current command
# Type part of a command, then press Ctrl+L — screen clears, your typed command remains

# Quick password entry — type a mistake
sudo vim /etc/nginx/nginx.conf
# Realize you mistyped the path
# Press Ctrl+A to go to start, navigate with Alt+F, fix the path

HISTSIZE and HISTFILESIZE

Control how many commands are saved:

# Current settings
echo "RAM history: $HISTSIZE"
echo "File history: $HISTFILESIZE"
echo "History file: $HISTFILE"

# Defaults: usually 1000 commands in RAM, 2000 in file

# Increase history size (add to ~/.bashrc)
export HISTSIZE=10000          # Keep 10000 commands in RAM
export HISTFILESIZE=20000      # Keep 20000 commands in ~/.bash_history

# Don't save duplicate consecutive commands
export HISTCONTROL=ignoredups

# Don't save both duplicate AND commands starting with space
export HISTCONTROL=ignoreboth
# Tip: prefix any command with a space to keep it out of history:
 my-secret-password-command    ← won't be saved in history

# Add timestamps to history
export HISTTIMEFORMAT="%Y-%m-%d %H:%M  "

# Append to history file (don't overwrite) — for multiple terminal sessions
shopt -s histappend

# Apply all changes
source ~/.bashrc

alias — Create Command Shortcuts

# Create a temporary alias (lasts until terminal is closed)
alias ll='ls -alh --color=auto'
alias gs='git status'
alias k='kubectl'

# See all current aliases
alias

# See a specific alias
alias ll
# alias ll='ls -alh --color=auto'

# Remove an alias
unalias gs

# Make aliases permanent (add to ~/.bashrc)
cat >> ~/.bashrc << 'EOF'

# ── Git Aliases ──────────────────────────────────────────
alias gs='git status'
alias ga='git add'
alias gc='git commit'
alias gp='git push'
alias gl='git log --oneline --graph --decorate --all'
alias gd='git diff'

# ── Navigation Aliases ───────────────────────────────────
alias ll='ls -alh --color=auto'
alias la='ls -A'
alias ..='cd ..'
alias ...='cd ../..'
alias ....='cd ../../..'

# ── System Aliases ───────────────────────────────────────
alias update='sudo apt update && sudo apt upgrade -y'
alias ports='ss -tlnp'
alias myip='curl -s ifconfig.me && echo'
alias diskuse='df -h | grep -v tmpfs'
alias memuse='free -h'

# ── Safety Aliases ───────────────────────────────────────
alias rm='rm -i'          # Always confirm deletions
alias cp='cp -i'          # Always confirm overwrites
alias mv='mv -i'          # Always confirm overwrites
EOF

source ~/.bashrc

Key Takeaways

  • history shows all past commands with numbers; history | grep keyword finds specific commands
  • !! repeats the last command; sudo !! is the most-used pattern (forgot sudo)
  • !string re-runs the most recent command starting with that string
  • !$ expands to the last argument of the previous command — great for mkdir then cd
  • Ctrl+R is reverse history search — type part of any previous command to find and run it
  • Ctrl+A / Ctrl+E — jump to start/end of line; Ctrl+K / Ctrl+U — delete to end/start
  • Set HISTSIZE=10000 and HISTTIMEFORMAT in ~/.bashrc to improve history usefulness
  • Aliases save time — define them in ~/.bashrc and source the file to apply
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