#![feature(core)]
#![feature(env)]
use std::env;
fn increase(number: i32) {
println!("{}", number + 1);
}
fn decrease(number: i32) {
println!("{}", number - 1);
}
fn help() {
println!("usage:
match_args <string>
Check whether given string is the answer.
match_args {{increase|decrease}} <integer>
Increase or decrease given integer by one.");
}
fn main() {
let args: Vec<String> = env::args().map(|x| x.to_string())
.collect();
match args.as_slice() {
// no arguments passed
[ref name] => {
println!("My name is '{}'. Try passing some arguments!", name);
},
// one argument passed
[_, ref string] => {
if string.as_slice() == "42" {
println!("This is the answer!");
} else {
println!("This is not the answer.");
}
},
// one command and one argument passed
[_, ref cmd, ref num] => {
// parse the number
let number: i32 = match num.parse() {
Ok(n) => {
n
},
Err(_) => {
println!("error: second argument not an integer");
help();
return;
},
};
// parse the command
match cmd.as_slice() {
"increase" => increase(number),
"decrease" => decrease(number),
_ => {
println!("error: invalid command");
help();
},
}
},
// all the other cases
_ => {
// show a help message
help();
}
}
}
$ ./match_args Rust
This is not the answer.
$ ./match_args 42
This is the answer!
$ ./match_args do something
error: second argument not an integer
usage:
match_args <string>
Check whether given string is the answer.
match_args {increase|decrease} <integer>
Increase or decrease given integer by one.
$ ./match_args do 42
error: invalid command
usage:
match_args <string>
Check whether given string is the answer.
match_args {increase|decrease} <integer>
Increase or decrease given integer by one.
$ ./match_args increase 42
43
For implementing more complicated, unix-like command line interfaces see the getopts example.