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Command line one-liners

29.11.2013

I attended the SoCraTes UK unconference. We had a space for lightning talks and I did a presentation about command line one-liners.

I love Unix and I was talking about terminal commands, so I used Terminal Keynote – a hack for terminal-based talks.

Contribute to the list with your own commands in the command line one-liners repository.

Terminal Keynote

Command line one-liners

Run the last command

$ !!

Run the last command as root

$ sudo !!

Create a script of the last executed command

$ echo "!!" > script.sh

Reuse all parameter of the previous command line

$ echo cd .
$ !*

Run the last command with some argument

$ echo a b c d e
$ echo !!:2
$ echo !!:3-$

Insert the last argument of the previous command

$ cp script.sh /usr/bin/
$ cd <ESC> .

Runs previous command but replacing

$ echo no typos
$ ^typos^errors

Escape any command aliases

$ alias ls="ls -a"
$ \ls

Quickly rename a file

$ mv filename.{old,new}
$ mv filename.{png,jpg}

Create a quick back-up copy of a file

$ cp file.txt{,.bak}

Run a command from the history

$ history
 ...
 1225  ls -l
 1226  git status
 1227  history
$ !-3
$ !1225

Search the history for the most recent command beginning with ‘text’

$ !text

List of commands you use most often

$ history | awk '{print $2}' | sort | uniq -c | sort -rn | head

Execute a command without saving it in the history

$ <space>command

Make directory including intermediate directories

$ mkdir -p a/long/directory/path

Create a directory and change into it

$ mkdir dir && cd $_

Change to the previous working directory

$ cd -

Jump to a directory. Execute a command. Jump back to current directory

$ (cd /tmp && ls)

Create simple text file from command line

$ cat > file.txt
{your text here}
{your text here}
<ctrl-d>

Empty a file

$ > file.txt

Show PATH in a human-readable way

$ echo $PATH | tr ':' '\n'
$ tr ':' '\n' <<< $PATH

Make ‘less’ behave like ‘tail -f’

$ less +F somelogfile

Redirect standard input to a file. Print it to standard output

$ command | tee file.txt | less

┌─────────┐  ┌─────────┐  ┌─────────┐
│ command │─▸│   tee   │─▸│ stdout  │
└─────────┘  └────┬────┘  └─────────┘
                  │
                  ▾
            ┌───────────┐
            │   file    │
            └───────────┘

Search for a string inside all files in the current directory

$ grep -RnsI --color=auto <pattern> *

Beyond grep

_   /|
\'o.O'
=(___)=
  U    ack!

$ ack <pattern>

Recursively remove all empty directories

$ find . -type d -empty -delete

Count your commits

$ git shortlog -sn

Serve current directory tree at http://$HOSTNAME:8000/

$ python -m SimpleHTTPServer

Share a file between two computers

$ nc -l 5566 > data-dump.sql
$ nc <his-ip-address> 5566 < data-dump.sql

Download an entire website

$ wget -m http://website.com

Clear the terminal screen

<ctrl-l>

Salvage a borked terminal

$ reset

Close shell keeping all subprocess running

$ disown -a && exit

Run a command immune to hangups

$ nohup command &

Attach screen over ssh

$ ssh user@host -t screen -r

Compare a remote file with a local file

$ ssh user@host cat /path/to/remotefile | diff /path/to/localfile -

Get your public IP address

$ curl ifconfig.me

Set audible alarm when an IP address comes online

$ ping -a IP_address

List programs with open ports and connections

$ lsof -i

Currently mounted filesystems in nice layout

$ mount | column -t

Display free disk space

$ df -h

Display disk usage statistics for the current directory

$ du -sh *

Display 10 biggest files/folders for the current directory

$ du -s * | sort -nr | head

Execute a command at a given time

$ echo "ls -l" | at midnight

Simple stopwatch

$ time read
<ctrl-d>

Put a console clock in top right corner

$ while sleep 1;do tput sc;tput cup 0 $(($(tput cols)-29));date;tput rc;done &

Display the top ten running processes. (Sorted by memory usage)

$ ps aux | sort -nk +4 | tail

Kill all Ruby processes

$ ps aux | grep ruby | awk '{ print $2 }' | xargs kill -9
$ ps aux | awk '/ruby/ && ! /awk/ { system("kill -9 "$2) }'

32 bits or 64 bits?

$ getconf LONG_BIT

Displays a calendar

$ cal 12 1984

What day is today?

$ cal | sed "s/.*/ & /;s/ $(date +%d) / [] /"
$ cal | sed "s/.*/ & /;s/ $(date +%d) / $(printf '\e[0;31m[]\e[0m') /"

Show File System Hierarchy

$ man hier

Quick access to the ascii table

$ man ascii

Russian Roulette in Bash

$ [ $[ $RANDOM % 6 ] == 0 ] && rm -rf / || echo "You live"

Watch Star Wars via telnet

$ telnet towel.blinkenlights.nl