diff --git a/lab5/user/lab5/apps/init.c b/lab5/user/lab5/apps/init.c
index 46fdec0..01a75c5 100644
--- a/lab5/user/lab5/apps/init.c
+++ b/lab5/user/lab5/apps/init.c
@@ -29,7 +29,8 @@ int fs_server_cap;
 #define FTYPE_FILE 0b01
 #define FTYPE_DIR  0b10
 
-static char *builtin_complement_word[] = {"cd", "ls", "ll", "cat", "echo", "clear"};
+static char *builtin_complement_word[] = {"cd", "ls", "ll", "cat", "echo", "clear", "pwd",
+                                          "exit", "quit"};
 static int n_builtin_complement_word = sizeof(builtin_complement_word) / sizeof(char *);
 
 static char file_complement_buf[MAX_FILE_COMPLEMENT_WORD * (MAX_FILENAME_LEN + 1)];
@@ -38,6 +39,9 @@ void path_to_absolute(char *path);
 void path_append(char *path, char *sub);
 int fs_scan(char *path);
 
+// 当前目录
+char working_directory[BUFLEN] = {'/'};
+
 /**
  * 生成文件补全词列表
  * @param ret_words 返回列表
@@ -131,8 +135,10 @@ static char *match_builtin_command_param(char *complement, int complement_time,
     while (complement[start_pos] == ' ')
         start_pos++;
     // 匹配子目录文件
-    n_words = make_file_complement_word(&words, complement + start_pos, type_mask);
-    matched = match_complement_words(words, n_words, complement + start_pos, complement_time, match_count);
+    if (*(complement + start_pos) != '\0') {
+        n_words = make_file_complement_word(&words, complement + start_pos, type_mask);
+        matched = match_complement_words(words, n_words, complement + start_pos, complement_time, match_count);
+    }
     // 匹配当前目录文件
     if (!matched) {
         n_words = make_file_complement_word(&words, NULL, type_mask);
@@ -157,8 +163,10 @@ static int do_complement(char *buf, char *complement, int complement_time)
     int n_words;
 
     // 匹配子目录内文件，如 tar 匹配 tar/file1
-    n_words = make_file_complement_word(&words, complement, FTYPE_FILE);
-    matched = match_complement_words(words, n_words, complement, complement_time, &match_count);
+    if (*complement != '\0') {
+        n_words = make_file_complement_word(&words, complement, FTYPE_FILE);
+        matched = match_complement_words(words, n_words, complement, complement_time, &match_count);
+    }
 
     // 匹配当前目录文件，如 f 匹配 file1
     if (!matched) {
@@ -260,15 +268,30 @@ char *readline(const char *prompt)
 
 int do_cd(char *cmdline)
 {
+    char pathbuf[BUFLEN];
 	cmdline += 2;
 	while (*cmdline == ' ')
 		cmdline++;
 	if (*cmdline == '\0')
 		return 0;
+    // 解析路径
 	if (*cmdline != '/') {
-	}
-	printf("Build-in command cd %s: Not implemented!\n", cmdline);
-	return 0;
+        // 相对路径
+        strcpy(pathbuf, working_directory);
+        path_append(pathbuf, cmdline);
+	} else {
+        // 绝对路径
+        strcpy(pathbuf, cmdline);
+    }
+    // 检查路径是否存在
+    int ret = fs_scan(pathbuf);
+    if (ret < 0) {
+        printf("'%s' is not a dir!\n", cmdline);
+        return -1;
+    }
+    // 切换
+    strcpy(working_directory, pathbuf);
+    return 0;
 }
 
 int do_top()
@@ -277,18 +300,24 @@ int do_top()
 	return 0;
 }
 
+int do_pwd()
+{
+    printf("%s\n", working_directory);
+    return 0;
+}
+
 /**
  * 转为绝对路径
  */
 void path_to_absolute(char *path) {
     char pathbuf[BUFLEN];
-    strcpy(pathbuf + 1, path);
-    pathbuf[0] = '/';
+    strcpy(pathbuf, working_directory);
+    path_append(pathbuf, path);
     strcpy(path, pathbuf);
 }
 
 /**
- * 路径连接
+ * 路径连接，sub 必须为相对路径且不支持 ..
  */
 void path_append(char *path, char *sub) {
     size_t path_len = strlen(path);
@@ -298,13 +327,19 @@ void path_append(char *path, char *sub) {
             path += path_len;
         } else {
             path[path_len] = '/';
-            path += path_len + 1;
+            path += ++path_len;
         }
     }
     // sub 之前没有 '/'
     while (*sub == '/') sub++;
     // 连接路径
     strcpy(path, sub);
+    path += strlen(sub);
+    path_len += strlen(sub);
+    // 路径末尾不能出现 '/'，个人感觉不是很合理，但是 tfs_open_path 行为如此
+    while (*--path == '/' && --path_len > 0) {
+        *path = '\0';
+    }
 }
 
 /**
@@ -551,6 +586,10 @@ int builtin_cmd(char *cmdline)
 		ret = do_top();
 		return !ret ? 1 : -1;
 	}
+    if (!strcmp(cmd, "pwd")) {
+        ret = do_pwd();
+        return !ret ? 1 : -1;
+    }
 	return 0;
 }