Userland: Add a simple /bin/head program.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/b5a1ee1d3e0

Userland/head.cpp

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char** argv)
+{
+    // FIXME: Allow setting via command-line argument.
+    int line_count = 10;
+
+    if (argc > 1) {
+        for (int i = 1; i < argc; ++i) {
+            if (argv[i][0] == '-') {
+                line_count = atoi(&argv[i][1]);
+            }
+        }
+    }
+
+    for (int line = 0; line < line_count; ++line) {
+        char buffer[BUFSIZ];
+        auto* str = fgets(buffer, sizeof(buffer), stdin);
+        if (!str)
+            break;
+        fputs(str, stdout);
+    }
+
+    return 0;
+}