Ruby/File Directory/IO.new

Mode    Description
r       Read-only. Starts at the beginning of the file (default mode).
r+      Read-write. Starts at the beginning of the file.
w       Write-only. Truncates existing file to zero length or creates a new file for writing.
w+      Read-write. Truncates existing file to zero length or creates a new file for reading and writing.
a       Write-only. Starts at the end of file if the file exists, otherwise creates a new file for writing.
a+      Read-write. Starts at the end of the file if the file exists, otherwise creates a new file for reading and writing.
b       (DOS/Windows only.) Binary file mode. May appear with any of the modes listed in this table.

Stream description              File descriptor             Predefined Ruby variable           Ruby environment variable
Standard input stream           0                           $stdin                             STDIN
Standard output stream          1                           $stdout                            STDOUT
Standard error output stream    2                           $stderr                            STDERR

# The first argument is 1, which is the numeric file descriptor for standard input. 
# Standard input can also be represented by the predefined Ruby variable $stdin. 
# The optional second argument, w, is a mode string meaning "write."
ios = IO.new( 1, "w" )
ios.puts "IO, IO, it"s off to the computer lab I go."
$stdout.puts "Do you copy?"