apps: Add a little ls utility that lists the files in /bin

apps/Makefile

@@ -1,4 +1,4 @@
-APPS := init sym sh crash uname uptime hello ps
+APPS := init sym sh crash uname uptime hello ps ls
 
 APPS_DIR := $(LUNA_ROOT)/apps
 APPS_SRC := $(APPS_DIR)/src

apps/src/ls.c

@@ -0,0 +1,28 @@
+#include <fcntl.h>
+#include <luna/dirent.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int main()
+{
+    int dirfd = open("/bin", O_RDONLY);
+    if (dirfd < 0)
+    {
+        perror("open");
+        return 1;
+    }
+    struct luna_dirent dirent[5];
+    ssize_t nread;
+    do {
+        nread = getdents(dirfd, dirent, 5);
+        if (nread < 0)
+        {
+            perror("getdents");
+            return 1;
+        }
+        for (int i = 0; i < nread; i++) { printf("%s\n", dirent[i].name); }
+    } while (nread == 5);
+
+    close(dirfd);
+    return 0;
+}