Set the Finder icon of a single file in macOS

setIcon.sh

#!/bin/sh
# Sets an icon for a file
# Parameters:
#   $1 icon_source - file path to the icon soruce (a .icns file)
#   $2 file_path   - file path the the destination file to change the icon of
icon_source=$1
file_path=$2

generated_icon=".icon.rsrc"

# Create rsrc file
DeRez -only icns $icon_source > $generated_icon

# Apply rsrc file
SetFile -a C "$file_path"
Rez -append $generated_icon -o "$file_path"

# Removed generated file
rm $generated_icon