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use std::env; extern "C" { fn c_func(input: i32) -> i32; } fn c_call(i:i32) -> i32{ unsafe { return c_func(i); } } fn main() { let args: Vec<String> = env::args().collect(); match args[1].parse::<i32>() { Ok(i) => println!("Absolute value of {} is {}",i, c_call(i)), Err(..) => println!("Wrong argument {}",args[1]), }; }