diff --git a/.gitignore b/.gitignore
index bdc5af0..62b545e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 *~
 build
+vgcore*
diff --git a/src/cat.c b/src/cat.c
index a7a9874..1c8fee2 100644
--- a/src/cat.c
+++ b/src/cat.c
@@ -1,18 +1,50 @@
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int usage(char *argv0) {
+  printf("Usage: %s [-u] [file ...]\n", argv0);
+  return 2;
+}
 
 int main(int argc, char *argv[]){
 	char ch;
-	for (int i = 1; i < argc; i++) {
-		FILE *file = fopen(argv[i], "r");
-		if (file == NULL ) {
-			printf("Cannot find file: %s\n", argv[1]);
-			return 1;
-		}
+  int opt;
+  FILE *file = stdin;
+  while ((opt = getopt(argc, argv, ":u")) != -1) {
+    switch (opt) {
+      case 'u':
+        break;
+      case '?':
+        fprintf(stderr, "%s: invalid option -- '%c'\n", argv[0], optopt);
+        return usage(argv[0]);
+    }
+  }
 
-		while ((ch = fgetc(file)) != EOF)
-       		{
-			putchar(ch);			
-			}
-		fclose(file);
-	}
+  if (optind == argc) { // FIXME: this code is not clean
+    goto READ_STDIN;
+  }
+
+  for (; optind < argc; optind++) {
+    if (strcmp(argv[optind], "-")) {
+      file = fopen(argv[optind], "r");
+      if (file == NULL) {
+        fprintf(stderr, "%s: ", argv[0]);
+        perror(argv[optind]);
+        return -1;
+      }
+    } else {
+      file = stdin;
+    }
+READ_STDIN:
+		while ((ch = fgetc(file)) != EOF) {
+			putchar(ch);
+		}
+    if (file != NULL && file != stdin) {
+      fclose(file);
+    }
+  }
+  return 0;
 }