``In the Beginning was the Command Line.''
[Title of a
marvelous essay by Neal Stephenson
(available online at
https://www.spack.org/essays/commandline.html).]
Regardless of the system in which Ruby is deployed, whether it be a
super high-end scientific graphics workstation or an embedded PDA
device, you've got to start the Ruby interpreter somehow, and that
gives us the opportunity to pass in command-line arguments.
A Ruby command line consists of three parts: options to the Ruby
interpreter, optionally the name of a program to run, and optionally a
set of arguments for that program.
ruby [
options
] [--] [
programfile
] [
arguments
]
|
The Ruby options are terminated by the first word on the command line
that doesn't start with a hyphen, or by the special flag ``
--''
(two hyphens).
If no filename is present on the command line, or if the filename is
a single hyphen (
-), Ruby reads the program source from standard
input.
Arguments for the program itself follow the program name. For example:
% ruby -w - "Hello World"
will enable warnings, read a program from standard input, and pass it
the quoted string
"Hello World" as an argument.
