Basic

Redirect operators

# pipe
echo "hello world" | sed 's/ /_/'

# redirect the standard output result to file (replace)
echo "hello world" > test.txt

# redirect the standard output result to file (append)
echo "hello world" >> test.txt

# redirect file to standard input
# e.g. replace all space to _ in text.txt and save to a new file
sed 's/ /_/g' < test.txt > test_1.txt

# line input
cat << end
heredoc> hello
heredoc> world
heredoc> end

Create multiple files or folders

mkdir sa{1..50}

# -p, --parents
#        no error if existing, make parent directories as needed
mkdir -p sa{1..50}/sax{1..50}
mkdir {a-z}12345 
mkdir {1,2,3}
mkdir test{01..10}
mkdir -p `date '+%y%m%d'`/{1,2,3} 
mkdir -p $USER/{1,2,3} 

Useful Commands

zsh

• Cheatsheet
• d to show directory history
  • type cd -number or directly type the number to go to directory
• !:n-m get the attribute from n to m of last command
• !! to get the last command
• !* to get the argz of last command
• zsh tip
• zsh - Table of Contents
• Customizing your shell prompt
• man page zshmisc section 1

tr

translate or delete characters

# replace "space character" to "+"
echo "hello world" | tr "[:blank:]" "+"

copydir

Custom Command: copydir to copy current directory to clipboard

function copydir {
  pwd | tr -d "\r\n" | pbcopy
}

qlmanage

# Quick-look a file from the command line
alias ql='qlmanage -p'

airport

sudo ln -s /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/sbin/airport

Scan your local wireless environment from the command line

pgrep and pkill

Find or signal a program or process by name

shutdown

Restart the Mac

shutdown -r now
# or

reboot

textutil

Convert between various text file formats

xargs

Granted, I often xargs at CLI to do the looping (KYLee):

# simple use case
echo "U R L" | xargs -n1 echo

# -I may be needed for more complex use case (`mv @ @.bak`)
# however -I implies -L (takes input as line)
# so split before call
echo "U R L" | sed 's/ /\n/g' | xargs -I@ echo @

# or do with temp file
echo "U\nR\nL" > file
cat file | xargs -I@ echo @

Find files and delete them

$ find . -name "FILE-TO-FIND" -exec rm -rf {} \;

tmux

tmux is a terminal multiplexer. It lets you switch easily between several programs in one terminal, detach them (they keep running in the background) and reattach them to a different terminal.

# list all session
tmux ls

# attach to session
tmux attach -t sessionName

# create new session
tmux new -s sessionName

# kill session
tmux kill-session -t sessionName

navigate in tmux

• Ctrl-b then [ then you can use your normal navigation keys to scroll around (eg. Up Arrow or PgDn).

• Press q to quit scroll mode.

• just quit terminal for exit the session

ImageMagick (convert)

Use ImageMagick to resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves.

# Example 1: convert image's format
convert image.jpg image.png

# Example 2: resize an image
# It is sometimes convenient to resize an image as they are read.
# Suppose you have hundreds of large JPEG images you want to convert
# to a sequence of PNG thumbails:
convert '*.jpg' -resize 120x120 thumbnail%03d.png
# rename file batchly

$ rename 's/\.html$/\.php/' *.html

# Example 3: convert images to gif
# convert 1.jpg, 2.jpg, 3.jpg, 4.jpg, and 5.jpg
# in your current directory to a GIF animation.
magick *.jpg images.gif

ffmpeg

ffmpeg A complete, cross-platform solution to record, convert and stream audio and video.

# -i mean input_file
$ ffmpeg -i input.mp4 output.avi

http-server

http-server is a simple, zero-configuration command-line http server. It is powerful enough for production usage, but it’s simple and hackable enough to be used for testing, local development, and learning.

youtube-dl

youtube-dl is a small command-line program to download videos from YouTube.com and a few more sites.

• Example | Download YouTube in batch

pt

A code search tool similar to ack and the_silver_searcher(ag). It supports multi platforms and multi encodings.

• Platinum Searcher

Pandoc

• Pandoc
• examples
• a universal document converter

http

HTTPie – command line HTTP client

# install
brew install httpie

caddy

caddy is the HTTP/2 web server with automatic HTTPS.

features

• proxy server
• websocket server
• redirect address

jq

Command-line JSON processor. It’s also very handy tool to parse JSON like lodash

• jq
• echo '{"name": "CyrusN"}'| jq .name
• http is commandline version of postman

top

using top command to kill running process

osx metadata

• mac OS X mdfind, mdutil, mdls, mdimport. file metadata utilities