open file with nonblock and add test

Author: reubenwong97

Cargo.lock

@@ -18,6 +18,7 @@ workspace = true
 path = "src/sync.rs"
 
 [dependencies]
+libc = { workspace = true }
 clap = { workspace = true }
 uucore = { workspace = true, features = ["wide"] }
 fluent = { workspace = true }

src/uu/sync/Cargo.toml

@@ -35,9 +35,9 @@ mod platform {
     #[cfg(any(target_os = "linux", target_os = "android"))]
     use nix::unistd::{fdatasync, syncfs};
     #[cfg(any(target_os = "linux", target_os = "android"))]
-    use std::fs::File;
+    use std::fs::{File, OpenOptions};
     #[cfg(any(target_os = "linux", target_os = "android"))]
-    use uucore::error::FromIo;
+    use std::os::unix::fs::OpenOptionsExt;
     #[cfg(any(target_os = "linux", target_os = "android"))]
     use uucore::translate;
 
@@ -57,7 +57,10 @@ mod platform {
     /// Logs a warning if fcntl fails but doesn't abort the operation.
     #[cfg(any(target_os = "linux", target_os = "android"))]
     fn open_and_reset_nonblock(path: &str) -> UResult<File> {
-        let f = File::open(path).map_err_context(|| path.to_string())?;
+        let f = OpenOptions::new()
+            .read(true)
+            .custom_flags(libc::O_NONBLOCK)
+            .open(path)?;
         // Reset O_NONBLOCK flag if it was set (matches GNU behavior)
         // This is non-critical, so we log errors but don't fail
         if let Err(e) = fcntl(&f, FcntlArg::F_SETFL(OFlag::empty())) {

src/uu/sync/src/sync.rs

@@ -167,3 +167,21 @@ fn test_sync_multiple_files() {
     // Sync both files
     new_ucmd!().arg("--data").arg(&file1).arg(&file2).succeeds();
 }
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+#[test]
+fn test_sync_data_fifo_fails_immediately() {
+    use std::time::Duration;
+    use uutests::util::TestScenario;
+    use uutests::util_name;
+
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+    at.mkfifo("testfifo");
+
+    ts.ucmd()
+        .arg("--data")
+        .arg(at.plus_as_string("testfifo"))
+        .timeout(Duration::from_secs(2))
+        .fails();
+}