In Rust, the std::process module provides functionality for working with the current process and spawning new processes. This challenge focuses on working with the current process - getting its ID, handling exit codes, and managing process information.

Every running process has a unique identifier (PID) assigned by the operating system. You can get the current process ID using std::process::id().

When a program terminates, it returns an exit code to the operating system:

• 0 typically indicates success
• Non-zero values indicate various types of failures

The std::process::ExitCode type provides a type-safe way to represent exit codes. You can also use std::process::exit() to terminate a program immediately with a specific exit code.

In extreme cases, you can use std::process::abort() to terminate the process abnormally. This is typically used when the program is in an unrecoverable state.

Implement the following functions to work with process information and exit codes:

1. get_process_id - Returns the current process ID as a u32

2. exit_code_success - Returns an ExitCode representing success (0)

3. exit_code_failure - Returns an ExitCode representing failure (1)

4. exit_code_from_u8 - Converts a u8 value to an ExitCode

5. is_success_code - Checks if a given u8 exit code represents success (0)

6. is_failure_code - Checks if a given u8 exit code represents failure (non-zero)

7. describe_exit_code - Returns a description string for common exit codes:

   • 0 -> "success"
   • 1 -> "general error"
   • 2 -> "misuse of command"
   • 126 -> "command not executable"
   • 127 -> "command not found"
   • 128 -> "invalid exit argument"
   • 130 -> "script terminated by ctrl-c"
   • Any other value -> "unknown exit code: N" (where N is the code)

8. validate_exit_code - Takes an Option<u8> and returns:

   • Ok(code) if Some and code is 0
   • Err("process failed with code N") if Some and code is non-zero
   • Err("process did not return an exit code") if None

use process_exit::*;
 
// Get current process ID
let pid = get_process_id();
assert!(pid > 0); // PID is always positive
 
// Create exit codes
let success = exit_code_success();
let failure = exit_code_failure();
let custom = exit_code_from_u8(42);
 
// Check exit codes
assert!(is_success_code(0));
assert!(!is_success_code(1));
assert!(is_failure_code(1));
assert!(!is_failure_code(0));
 
// Describe exit codes
assert_eq!(describe_exit_code(0), "success");
assert_eq!(describe_exit_code(127), "command not found");
assert_eq!(describe_exit_code(42), "unknown exit code: 42");
 
// Validate exit codes
assert_eq!(validate_exit_code(Some(0)), Ok(0));
assert_eq!(
    validate_exit_code(Some(1)),
    Err("process failed with code 1".to_string())
);
assert_eq!(
    validate_exit_code(None),
    Err("process did not return an exit code".to_string())
);