return to 2021 features, and add replace old way to detect error when trying to open fifo file

01_phase_rust_src/sv/Cargo.toml

@@ -1,9 +1,10 @@
 [package]
 name = "sv"
 version = "0.2.0"
-edition = "2024"
+edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
 tokio = { version = "1.37.0", features = ["full"] }
+libc = "0.2"

01_phase_rust_src/sv/src/status_obj/misc.rs

@@ -1,6 +1,4 @@
 
-use std::io::ErrorKind;
-
 use tokio::net::unix::pipe;
 use tokio::runtime::Runtime;
 
@@ -85,18 +83,14 @@ pub fn check_fifo(sv: String, path: &str) -> bool {
 
     let sender = pipe::OpenOptions::new().open_sender(path);
     match sender {
-        Ok(..) => {},
-        Err(e) => match e.kind() {
-            ErrorKind::NotFound => {
-                println!("warning: {sv}: unable to open {path}: file does not exist");
-                return false;
-            },
-            _ => {
-                println!("fail: {sv}: runsv not running");
-                return false;
-            }
+        Ok(..) => return true,
+        Err(e) if e.raw_os_error() == Some(libc::ENXIO) => {
+            println!("fail: {sv}: runsv not running");
+            return false;
+        },
+        Err(..) => {
+            println!("warning: {sv}: unable to open {path}: file does not exist");
+            return false;
         },
     };
-
-    return true
 }