Shell Check Program Exists

Use program to do this:

# Output on whether the command exists
command -v echo

# Do something if the command is installed
if [ -x "$(command -v git)" ]; then
  git clone "https://github.com/kranners/frappuccino.git"
fi

# Do something if the command is not installed
if ! [ -x "$(command -v git)" ]; then
  echo 'Error: git is not installed.' >&2
  exit 1
fi