Fuzz the expr command

fuzz/fuzz_targets/fuzz_common.rs

@@ -0,0 +1,30 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use std::process::Command;
+use std::sync::atomic::Ordering;
+use std::sync::{atomic::AtomicBool, Once};
+
+static CHECK_GNU: Once = Once::new();
+static IS_GNU: AtomicBool = AtomicBool::new(false);
+
+pub fn is_gnu_cmd(cmd_path: &str) -> Result<(), std::io::Error> {
+    CHECK_GNU.call_once(|| {
+        let version_output = Command::new(cmd_path).arg("--version").output().unwrap();
+
+        println!("version_output {:#?}", version_output);
+
+        let version_str = String::from_utf8_lossy(&version_output.stdout).to_string();
+        if version_str.contains("GNU coreutils") {
+            IS_GNU.store(true, Ordering::Relaxed);
+        }
+    });
+
+    if IS_GNU.load(Ordering::Relaxed) {
+        Ok(())
+    } else {
+        panic!("Not the GNU implementation");
+    }
+}