diff --git a/include/string.h b/include/string.h
index c4a93bd..cfca4d3 100644
--- a/include/string.h
+++ b/include/string.h
@@ -15,5 +15,8 @@ size_t strlen(const char *str);
 int strncmp(const char *s1, const char *s2, size_t len);
 char *strncpy(char *to, const char *from, size_t len);
 
+char *strcat(char *s, const char *append);
+char *strncat(char *s, const char *append, size_t count);
+
 #endif /* __STRING_H__ */
 
diff --git a/lib/libc/string.c b/lib/libc/string.c
index ec3730b..4731b68 100644
--- a/lib/libc/string.c
+++ b/lib/libc/string.c
@@ -2,6 +2,8 @@
  * Copyright (c) 2013-2014 Stanford University
  * Copyright (c) 2006-2008 Ali Mashtizadeh
  * All rights reserved.
+ *
+ * XXX: add BSD copyright
  */
 
 #include <stddef.h>
@@ -43,6 +45,41 @@ strncpy(char *to, const char *from, size_t length)
     return save;
 }
 
+char *
+strcat(char *s, const char *append)
+{
+    char *save = s;
+ 
+    for (; *s; ++s);
+    while ((*s++ = *append++));
+
+    return save;
+}
+
+
+char *
+strncat(char *dst, const char *src, size_t n)
+{
+    if (n != 0) {
+	char *d = dst;
+	const char *s = src;
+
+	while (*d != 0)
+	    d++;
+
+	do {
+	    if ((*d = *s++) == 0)
+		break;
+
+	    d++;
+	} while (--n != 0);
+
+	*d = 0;
+    }
+
+    return dst;
+}
+
 int
 strcmp(const char *s1, const char *s2)
 {