how to return current working directory from function? - rust

Question

has experience with high level programming languages. I read the Rust book and now trying to survive and understand how the "things" in Rust works. I would love that someone explain what the heck is - Ok(()) and how to deal with it? My goal is to return result from function in to the variable where the output:
Finished dev [unoptimized + debuginfo] target(s) in 0.01s
Running `target/debug/rcp ./file/ aba`
Ok(
"/home/tomand/rcp",
)
Here is the full code:
use std::fs;
use std::env;
use serde_json;
use regex::Regex;
use std::path::Path;
fn determinate_file_size(file: &str) -> u64 {
fs::metadata(file).unwrap().len()
}
fn determinate_is_it_file_or_dirctory(arg: &str) -> &str {
let file = "File";
let dir = "Directory";
let re = Regex::new(r"/").unwrap();
if re.is_match(arg) {
return dir;
}
return file;
}
fn collect_user_arguments() -> Vec<String> {
env::args().collect()
}
fn check_if_arguments_count_valid(args: &Vec<String>) -> bool {
if args.len() == 3 {
return true
}
help();
return false
}
fn get_current_working_dir() -> Result<T> {
env::current_dir()
}
fn help() {
println!("Examples:");
println!("rcp [srcfile] [destfile]");
println!("rcp [srcdir]/[srcfile] [destdir]/[destfile]");
}
fn main() {
let WORKING_DIR = get_current_working_dir();
let args: Vec<String> = collect_user_arguments();
if check_if_arguments_count_valid(&args) {
let arg1 = &args[1];
let arg2 = &args[2];
println!("{:#?}", determinate_is_it_file_or_dirctory(&arg1));
}
}
Seems the compiler tried to give me some inspiration but eventually we miscommunicate in the end:
error[E0107]: this enum takes 2 generic arguments but 1 generic argument was supplied
--> src/main.rs:42:33
|
42 | fn get_current_working_dir() -> Result<T> {
| ^^^^^^ - supplied 1 generic argument
| |
| expected 2 generic arguments
EDIT:
I went with this approach:
fn get_current_working_dir() -> String {
let res = env::current_dir();
match res {
Ok(path) => path.into_os_string().into_string().unwrap(),
Err(_) => "FAILED".to_string()
}
}
It seems more practice is required to understand the Result type and how to manage it.

Answer 1

std::env::current_dir returns a std::io::Result<Pathbuf>, so you need to use that type in your wrapper method:
fn get_current_working_dir() -> std::io::Result<PathBuf> {
env::current_dir()
}
Playground
Other nitpick:
const is not a type so let WORKING_DIR: const = get_current_working_dir(); is wrong, just let WORKING_DIR = get_current_working_dir(); is enough.