Command Line Jiu Jitsu

Inspired by Command Line Kung Fu.

All examples assume darwin system using bash. I also use fish and zsh, so most examples should work across shells.

Ag

The silver searcher.

ag <pattern> <path>

Disks

How big is this?

du -sh <path or file>

Estimate the size of every directory or file in the current directory

du -sh *

Finding X

grep <term> <file>

File/dir search: ls piped to grep

ls | grep <file/dir name>

Recursive (and better) file/dir search: find

find . -name "<term>"

touch

Create file(s), or update the date that a file was modified.

touch README.md index.html index.css app.js Dockerfile

tmux

Terminal multiplexer. Useful for disconnecting from ssh sessions without terminating a process or script. Can also be used as a window manager, e.g. creating panes, tabs, etc. and moving between them.

Create session:

tmux new -s <name>

Attach:

tmux a -t <name>

Detach:

Hotkeys: ctrl + b then ` d`

List sessions:

tmux ls

Kill session:

tmux kill-session -t <name>

screen

Create named session:

screen -S <session-name>

Detach with ctrl + A, d.

List sessions:

screen -ls

Attach to named session:

screen -x -S <session-name>

Kill named session:

screen -X -S <session number> quit

Attach to session (if there is only one):

screen -r

ping

ping www.google.com -c 3

cat

Concatenate (smash) files together:

$ ls
# one.csv
# two.csv
# three.csv

$ cat *.csv >> all.csv

Sort by unique (-u) lines:

$ sort -u all.csv > sorted_all.csv

history

history > weird_hotfix_that_I_will_never_remember.txt

tesseract

Tesseract is an open source optical character recognition (OCR) command line tool that uses the libtesseract OCR engine.

Convert image to searchable PDF

Take your image and convert it to a TIFF or JPG.

tesseract document_image.tif output pdf

OCR in other languages

Run tesseract with the -l to specify a language other than english. List of languages with their 3-character ISO 639-2 language codes.

openSSL

Generate a password with openSSL

openssl rand -base64 48 | cut -c1-${1}

–you may specify character length too, here it is 48.

Use alias for making a password generator

$ cd ~
$ echo "alias pgen='openssl rand -base64 48 | cut -c1-${1}'" >> .bash_profile

in a new terminal

$ pgen
sp8RiuHA+FbTDP/P7YUL7WWEgKTnfT2NjbT2JOf657O94Zvto/q1r7A3ctbPc9qc

vi & vim

The following simplified list of commands are for getting up and running fast, for more thorough vi cheat sheets see the links here and here.

running vim or vi

$ vim

$ vi

–the editor will open in normal mode, to enter ‘insert’ mode type i and enter in some text. To save and quit, press ESC followed by : then enter the letters w (save) and q (quit) then press enter.

Note: difference between vim and vi?

char nav

h move cursor left

l move cursor right

k move up

j move down

word nav

w moves to the start of next word

e moves to the end of the word

b moves to beginning of the word

document nav

H move to top of screen

L move to bottom of screen

gg jump to the first line of the document

G jump to the last line of the document

<number>G will jump directly to that line number, so 12G will jump to line 12 in your code.

line nav

0 jump to the start of the current line

A append to the end of current line

$ jump to the end of a line

searching

/ to search and n to go to the next occurance of the search, N to go in reverse. Regex can be used in searching.

% will jump to the first occurance of parentheses or brackets.

With * you can jump to the next occurance of the word your cursor is over, and # for the previous occurance. As an example, if you want to find the word “for” you can type /for to jump to the first occurance of “for”, then use * to cycle through the next occurance and # to the previous. For searching with / you can use n and N to cycle through the next and previous occurance, respectively.

miscellaneous

o to insert a new line below the current line your on, and enter insert mode.

O to insert a new line above the current line your on, and enter insert mode.

saving

:w save (write) the file

:wq save and quit

:q quit

:q! quit and toss away unsaved changes

:saveas file save as file

:help keyboard open help

For more information on vim and vi commands, usage, and to understand the vi language, visit this very very helpful stack overflow post.

vim enhancements

color

$ cd ~
$ echo "syntax on" >> .vimrc

You can even choose your own color scheme.

line numbers and tabs

Here are some other vim settings to enrich the experience:

$ cd ~
$ vim .vimrc

and add the following lines

set number
set expandtab
set tabstop=4
set softtabstop=4
set shiftwidth=4
set autoindent
set showmatch

Find more information here.

Note If you are looking for a feature-packed, colorful, modern, and professional vim experience, check out my current oh my vim configuration.

zip

Compress everything in current directory, as “foo.zip”

zip -r foo.zip .

extract “foo.zip”

unzip foo.zip

git

This is a breif outline of the basic git commands used in a trivial case.

clone a remote repo

git clone https://github.com/something.git

Makes a local copy of the remote repo somehting.

make your own branch

git checkout -b my_branch

Makes a new branch in your local cloned repo, and swiches from master branch to your newly created branch.

list branches

git branch

List the local branches, and notes the current branch you are in. To list local and remote branches, use git branch -a.

pushing to remote repo

git push origin my_branch

Pushes the new branch to the remote repo, other users can now access your branch, but only if your report repo is accessible to them.

switch to another branch

git checkout branch_name

Switch to branch_name.

merging branches

If you want to merge changes from master with your local changes in your branch, then do:

git checkout my_branch

..navegate to my_branch

git merge master

..and merge with master, which pulls commits from master into the active local branch, my_branch.

view git logs

git log

Will display the record of commits.

undo local changes

git checkout -- {filename}

Overwrite uncommited, unstaged changes for a single file. Pulls from the most recent local commit (HEAD). Reverts a single file to the last commited state, working directory is changed!

undo add

git reset HEAD

Clears the index, i.e. undo ‘git add’ for all staged changes. Working directory is not changed.

undo commit

git reset --soft HEAD^

Working directory is not changed, this points HEAD to the previous commit. Index is NOT reset, staged changes are still in index.

completely start over

git reset --hard HEAD

Clear all changes since the last commit, reset index, reset the working directory, throw out all changes and work, start over from the last commit.

Note: if you would like to show the current git repo status in your bash prompt, visit this page

Networking

Misc.

Cool tools/utilities that I plan to write about (some are brew specific packages):

Contact

simondkeng@gmail.com