Add --list flag to multicall binary

src/bin/util-linux.rs

@@ -21,7 +21,10 @@ include!(concat!(env!("OUT_DIR"), "/uutils_map.rs"));
 
 fn usage<T>(utils: &UtilityMap<T>, name: &str) {
     println!("{name} {VERSION} (multi-call binary)\n");
-    println!("Usage: {name} [function [arguments...]]\n");
+    println!("Usage: {name} [function [arguments...]]");
+    println!("       {name} --list\n");
+    println!("Options:");
+    println!("      --list    lists all defined functions, one per row\n");
     println!("Currently defined functions:\n");
     #[allow(clippy::map_clone)]
     let mut utils: Vec<&str> = utils.keys().map(|&s| s).collect();
@@ -123,6 +126,11 @@ fn main() {
                     }
                     usage(&utils, binary_as_util);
                     process::exit(0);
+                } else if util == "--list" {
+                    for util_name in utils.keys() {
+                        println!("{util_name}");
+                    }
+                    process::exit(0);
                 } else {
                     not_found(&util_os);
                 }

tests/tests.rs

@@ -90,3 +90,20 @@ mod test_mcookie;
 #[cfg(feature = "uuidgen")]
 #[path = "by-util/test_uuidgen.rs"]
 mod test_uuidgen;
+
+#[test]
+fn test_list() {
+    let out = std::process::Command::new(TESTS_BINARY)
+        .arg("--list")
+        .output()
+        .unwrap();
+    assert!(out.status.success());
+    let stdout = String::from_utf8(out.stdout).unwrap();
+    let lines: Vec<&str> = stdout.lines().collect();
+    assert!(!lines.is_empty());
+    // Can be replaced with lines.is_sorted() starting with Rust 1.82.
+    assert!(lines.windows(2).all(|w| w[0] <= w[1]));
+    // Spot-check a few utilities that should always be present.
+    assert!(lines.contains(&"rev"));
+    assert!(lines.contains(&"dmesg"));
+}