Interacting with the operating system

Some of the things you must be able to do when writing apps include getting information at startup, starting up a different program from within your app, and using the OS clipboard. Here, we'll show you how this is done in Red.

Getting input from command-line arguments

Command-line arguments are captured in the system/script/args word. It is one string in which all arguments are stored, separated by a space:

;-- see Chapter10/args.red:
print system/script/args           ;== "78 A Red"
type? system/script/args           ;== string!
args: split system/script/args " ";== ["78" "A" "Red"]
print ["Number of command-line arguments:"length? args]
                                   ;== Number of command-line arguments: 3
foreach arg args [
print arg
]
; 78
; A
; Red

We can use split to obtain the separated arguments in an args series, and start using them.

To see the output, start the program with red args.red 78 A Red, or after compiling with red -r, start it with...