Command skeleton
- Rust course
- Intermediate
- Lesson 60/115
- 6 min
Set up basic command reading with args.
Notebook CLI: skeleton
In this project we'll write a command-line notebook: not ekle süt al, not liste, not sil 2, not ara süt. Arguments come from std::env::args(); the first element is the program path:
let args: Vec<String> = std::env::args().collect();
// $ not liste → ["not", "liste"]
let komut = args.get(1).map(|s| s.as_str()).unwrap_or("yardim");To keep the program from crashing when no command is given, we use get(1) and default to yardim. In the exercises we'll pass arguments as a hand-built vector.
Handling arguments as a slice
Putting the command handler in a function taking &[String] makes it testable: main passes the real arguments, tests pass fake ones:
fn komut_adi(args: &[String]) -> &str {
args.get(1).map(|s| s.as_str()).unwrap_or("yardim")
}
fn main() {
let args: Vec<String> = std::env::args().collect();
println!("{}", komut_adi(&args));
}Practice Command name
Write the komut_adi function above. Print the results for two Vec<String>s containing ["not", "liste"] and just ["not"], separated by a space.
Starter code
fn main() {
// buraya yaz
}Sample solution
fn komut_adi(args: &[String]) -> &str {
args.get(1).map(|s| s.as_str()).unwrap_or("yardim")
}
fn main() {
let a = vec![String::from("not"), String::from("liste")];
let b = vec![String::from("not")];
println!("{} {}", komut_adi(&a), komut_adi(&b));
}Expected output
liste yardim
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Why use <code>args.get(1)</code> instead of <code>args[1]</code>?
- It's faster
- args[1] doesn't compile
- It returns a String
- If no command is given, you get None instead of a panic Correct answer
Explanation: User input can always be missing; the program should give a friendly help message.
2 Collect the arguments
let args: Vec<String> = std::env::____().collect();let args: Vec<String> = std::env::args().collect();Explanation: std::env::args() yields the program arguments as Strings.
3 Command line and args
| Term | Meaning |
|---|---|
not liste |
["not", "liste"] |
not |
["not"] |
not ekle süt |
["not", "ekle", "süt"] |
args.get(5) |
None |