# Keep the system awake.
caffeinate
caffeinate -t 600

# Do a network speed test.
networkquality -sv

# List open ports.
netstat
netstat -n -p 'tcp'
lsof -n -i ':443'
sudo lsof -n -i 'TCP' -s 'TCP:LISTEN'

# Get the PID of processes using specific ports.
lsof -nt -i ':443'

# Install Xcode CLI tools.
xcode-select --install

# Show Xcode tools's path.
xcode-select -p

# Remove Xcode tools.
sudo rm -rf $(xcode-select -p)

# List all available updates.
softwareupdate --list --all

# Install all recommended updates, agreeing to software license agreement
# without interaction, and automatically restart if required.
softwareupdate --install --recommended --restart --agree-to-license

# Download (but not install) recommended updates.
softwareupdate --download --recommended

# Check an NFS share is available on the network.
showmount -e 'host'

# Mount an NFS share.
sudo mount -t 'nfs' 'host:/path/to/share' 'path/to/mount/point'
sudo mount -t 'nfs' -o 'rw,resvport' 'host:/path/to/share' 'path/to/mount/point'

# Install a .pkg file from CLI.
# 'target' needs to be a device, not a path.
installer -pkg /path/to/non-root-package.pkg -target CurrentUserHomeDirectory
sudo installer -pkg /path/to/root-needed-package.pkg -target /

# Clear the DNS cache.
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

# Add a password to the default keychain.
# The password needs to be left last.
security add-generic-password -a johnny -s github -w 'b.good'

# Add a password to the default keychain giving it some optional data.
security add-generic-password -a johnny -s github -l work \
  -j 'my key for work' -w 'b.good'

# Update passwords' value.
security add-generic-password -a johnny -s github -l work -U -w 'new-pass'

# Print passwords to stdout.
security find-generic-password -w -a johnny -s github
security find-generic-password -w -l work
security find-generic-password -w -l work -s github

# Delete a password from the default keychain.
security delete-generic-password -a johnny -s github

# Get the host's bonjour name.
scutil --get LocalHostName
/usr/libexec/PlistBuddy -c "Print :System:Network:HostNames:LocalHostName" \
  /Library/Preferences/SystemConfiguration/preferences.plist

# Get the host's netbios name.
defaults read /Library/Preferences/SystemConfiguration/com.apple.smb.server NetBIOSName
/usr/libexec/PlistBuddy -c "Print :NetBIOSName" \
  /Library/Preferences/SystemConfiguration/com.apple.smb.server.plist

# Get the host's computer name.
scutil --get ComputerName
/usr/libexec/PlistBuddy -c "Print :System:System:ComputerName" \
  /Library/Preferences/SystemConfiguration/preferences.plist

# Get environment variables from inside launchd.
launchctl getenv 'key'
launchctl export

# Set environment variables inside of launchd.
launchctl setenv 'key' 'value'
launchctl unsetenv 'key' 'value'

# List all loaded jobs.
launchctl list

# List Mach bootstrap services only.
launchctl bslist
launchctl bstree

# Start jobs.
launchctl start 'job_label'

# Stop jobs.
launchctl stop 'job_label'

Hidden settings

Note: once set something, you'll probably need to restart the dock with killall Dock

# Show hidden apps indicators in the dock.
defaults write com.apple.dock showhidden -bool TRUE

# Reset changes to the dock.
defaults delete com.apple.dock

# Change the number of columns and rows in the springboard.
defaults write com.apple.dock springboard-columns -int 9
defaults write com.apple.dock springboard-rows -int 7

# Reset changes to the launchpad.
defaults delete com.apple.dock springboard-rows
defaults delete com.apple.dock springboard-columns
defaults write com.apple.dock ResetLaunchPad -bool TRUE

# Force Finder to always display hidden files.
defaults write com.apple.finder AppleShowAllFiles TRUE

Resize an image

From CLI:

# Retain ratio.
# Save as different file.
sips -Z '1000' -o 'resized.jpg' 'IMG_20190527_013903.jpg'

Resize a PDF file from Preview

In the Preview app:

Open the PDF file you want to compress.
Choose File > Export.
Do not choose Export as PDF.
Click the Quartz Filter pop-up menu, then choose Reduce File Size.
Click the Export button.

Update the OS from CLI

# List all available updates.
softwareupdate --list --all

# Install all recommended updates.
# Agree to software license agreement without interaction.
# Automatically restart if required.
softwareupdate --install --recommended --restart --agree-to-license

# Download (but not install) recommended updates.
softwareupdate --download --recommended

Keychain access from CLI

Save a password with the following settings:

user (a.k.a. account): johnny
password: b.good
service name: github
[optional] entry name (a.k.a. label): work; if not given, the service name will be used
[optional] comment: my key for work; if not given, it will be left blank

The password's value needs to be given last.

# Add the password to the default keychain.
security add-generic-password -a johnny -s github -w 'b.good'
# Also give it some optional data.
security add-generic-password -a johnny -s github -l work \
  -j 'my key for work' -w 'b.good'
# Update passwords' value.
security add-generic-password -a johnny -s github -l work -U -w 'new-pass'

# Print the above password to stdout.
security find-generic-password -w -a johnny -s github
security find-generic-password -w -l work
security find-generic-password -w -l work -s github

# Delete it.
security delete-generic-password -a johnny -s github

Check the share is available on the network:
```
showmount -e 'host'
```

Mount the share:

Using the CLI:

mkdir -p 'path/to/mount/point'
sudo mount -t 'nfs' 'host:/path/to/share' 'path/to/mount/point'
sudo mount -t 'nfs' -o 'rw,resvport' 'host:/path/to/share' 'path/to/mount/point'

Use TouchID to authenticate in the terminal

Add the pam_tid.so module as sufficient to /etc/pam.d/sudo:

# sudo: auth account password session
+auth       sufficient     pam_tid.so
auth       sufficient     pam_smartcard.so
auth       required       pam_opendirectory.so

This file is normally read-only, so saving your changes may require you to force the save (e.g. vim will require the use of wq! when saving).

Fix iTerm2

iTerm2 from version 3.2.8 comes with a reattach advanced feature which is incompatible with the addition of the pam_tid.so module alone.

You can either:

disable the feature: iTerm2 > Preferences > Advanced > (Goto the Session heading) > Allow sessions to survive logging out and back in

install and enable the pam_reattach.so module as optional to /etc/pam.d/sudo:

# pick one
brew install pam-reattach
sudo port install pam-reattach

# sudo: auth account password session
+auth       optional       /opt/local/lib/pam/pam_reattach.so ignore_ssh
+auth       sufficient     pam_tid.so
auth       sufficient     pam_smartcard.so
auth       required       pam_opendirectory.so

Note that when the module is not installed in /usr/lib/pam or /usr/local/lib/pam (e.g. on M1 Macs where Homebrew is installed in /opt/homebrew), you must specify the full path to the module in the PAM service file.

Xcode CLI tools

xcode-select --install

The tools will be installed into /Library/Developer/CommandLineTools by default, with the binaries being available at $(xcode-select -p)/usr/bin/.

Headless installation

# Force the `softwareupdate` utility to list the Command Line Tools.
touch /tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress

# Get their label.
CLI_TOOLS_LABEL="$(/usr/sbin/softwareupdate -l \
 | grep -B 1 -E 'Command Line Tools' \
 | awk -F'*' '/^ *\\*/ {print $2}' \
 | sed -e 's/^ *Label: //' -e 's/^ *//' \
 | sort -V \
 | tail -n1)"

# Install them.
/usr/sbin/softwareupdate -i --agree-to-license "$CLI_TOOLS_LABEL"

Removal

sudo rm -rf "$(xcode-select -p)"
sudo rm -rf '/Library/Developer/CommandLineTools'

Upgrade

See How to update Xcode from command line for details.

# Remove and reinstall.
sudo rm -rf "$(xcode-select -p)"
xcode-select --install

Boot keys cheatsheet

Only available on Intel based Macs.

To use any of these key combinations, press and hold the keys immediately after pressing the power button to turn on your Mac, or after your Mac begins to restart. Keep holding until the described behavior occurs.

Combination	Behaviour
`⌥ Option` or `Alt`	Start to Startup Manager, which allows you to choose other available startup disks or volumes. If your Mac is using a firmware password, you're prompted to enter the password
`⌥ Option` + `⌘ Command` + `P` + `R`	Reset the NVRAM or PRAM. If your Mac is using a firmware password, it ignores this key combination or starts up from Recovery
`⇧ Shift`	Start in safe mode. Disabled when using a firmware password
`⌘ Command` + `R`	Start from the built-in Recovery system
`⌥ Option` + `⌘ Command` + `R` or `⇧ Shift` + `⌥ Option` + `⌘ Command` + `R`	Start from Recovery over the Internet. It installs different versions of macOS, depending on the key combination you use while starting up. If your Mac is using a firmware password, you're prompted to enter the password
`⏏ Eject` or `F12` or `mouse button` or `trackpad button`	Eject a removable media, such as an optical disc. Disabled when using a firmware password
`T`	Start in target disk mode. Disabled when using a firmware password
`⌘ Command` + `V`	Start in verbose mode. Disabled when using a firmware password
`D`	Start to Apple Diagnostics
`⌥ Option` + `D`	Start to Apple Diagnostics over the Internet. Disabled when using a firmware password
`N`	Start from a NetBoot server, if your Mac supports network startup volumes. Disabled when using a firmware password
`⌥ Option` + `N`	Start from a NetBoot server and use the default boot image on it. Disabled when using a firmware password
`⌘ Command` + `S`	Start in single-user mode. Disabled in macOS Mojave or later, or when using a firmware password

Sources

All the references in the further readings section, plus the following:

README.md

Mac OS X

Table of contents

TL;DR