Terminal applications use Standard I/O, frequently notated as stdio, to read and write text to the terminal. For those who are new to working with consoles, stdio typically consists of three streams: stdin, stdout, and stderr.

“Standard out” is where a program writes its output. In ruby, when you run puts, it implicitly writes to $stdout.puts, which displays text in the users terminal.

Terminalwire replaces $stdout.puts in Thor with Terminalwire::Server::Resource::STDOUT#puts to stream output over WebSockets to the client. This allows you to write to the terminal as you would in a normal terminal application.

# Print "Hello, World!" to the terminal and append a newline
puts "Hello, World!"
# Print "Hi!" to the terminal without a newline
print "Hi!"

“Standard in” is where a program reads its input. In ruby, when you run gets, it implicitly reads from $stdin.gets, which reads text from the users terminal.

print "What is your name?: "
# Read a line of text from the terminal
name = gets.chomp # chomp removes the newline character
# Print a greeting to the terminal
puts "Hello, #{name}!"

When you need to read a password from the terminal, you can use the getpass method in Thor. This method will prompt the user for a password and return the value as a string without showing the users input on their terminal. This prevents people from seeing the password as it is typed.

puts "Login to your account"
# Read a line of text from the terminal
password = getpass # chomp removes the newline character
# Check if the password is correct.
if password == "password"
  puts "You are logged in"
else
  puts "Incorrect password"
end

“Standard error” is where a program writes its error messages. In ruby, when you run warn, it implicitly writes to $stderr.puts, which displays text in the users terminal.

# Write an error message to the users terminal
warn "Oops, An error occurred"