diff --git a/include/files.h b/include/files.h
index 3f2b70d..713bc03 100644
--- a/include/files.h
+++ b/include/files.h
@@ -14,11 +14,11 @@ class FilesOperation {
     void initialize_rootinode();
     void printDirectory(u_int64_t);
     u_int64_t create_new_inode(u_int64_t parent_inode_number, const char* name, mode_t mode);
-    // int unlink_inode(u_int64_t inode_number);
+    void unlink_inode(u_int64_t inode_number);
     u_int64_t namei(const char* path);
     u_int64_t fischl_mkdir(const char*, mode_t);
     u_int64_t fischl_mknod(const char*, mode_t);
     //int fischl_readdir(const char *, void *, fuse_fill_dir_t, off_t, struct fuse_file_info *, enum fuse_readdir_flags);
-    //int fischl_unlink (const char *);
+    int fischl_unlink (const char *);
     //int fischl_open (const char *, struct fuse_file_info *);
 };
\ No newline at end of file
diff --git a/lib/files.cpp b/lib/files.cpp
index 3ce2cb6..4a9e11f 100644
--- a/lib/files.cpp
+++ b/lib/files.cpp
@@ -294,4 +294,77 @@ u_int64_t FilesOperation::fischl_mknod(const char* path, mode_t mode) {
     u_int64_t ret = create_new_inode(parent_inode_number, newFilename, mode);
     delete pathdup;
     return ret;
+}
+
+void FilesOperation::unlink_inode(u_int64_t inode_number) {
+    INode inode;
+    inode.inode_construct(inode_number, disk);
+    if ((inode.permissions & S_IFMT) == S_IFDIR) {
+        char buffer[IO_BLOCK_SIZE] = {0};
+        for(u_int64_t idx=0; idx<inode.size; idx++) {
+            read_datablock(inode, idx, buffer);
+            DirectoryEntry ent;
+            for(int i=0;i<=IO_BLOCK_SIZE-64;i+=64){
+                if(ent.inode_number && strcmp(ent.file_name,".") && strcmp(ent.file_name,"..")){
+                    unlink_inode(ent.inode_number);
+                }
+            }
+        }
+    }
+    while(inode.size != 0) {
+        inode.datablock_deallocate(disk);
+        inode.size--;
+    }
+    inop.inode_free(disk, inode_number);
+}
+
+int FilesOperation::fischl_unlink(const char* path) {
+    char *pathdup = strdup(path);
+    char *lastSlash = strrchr(pathdup, '/');
+    *lastSlash = '\0';
+    char *filename = lastSlash+1;
+    char *ParentPath = pathdup;
+    if (!strcmp(filename,".")||!strcmp(filename,"..")) {
+        printf("refusing to remove . or ..\n");
+        return -1;
+    }
+    u_int64_t parent_inode = namei(ParentPath);
+    if (parent_inode == (u_int64_t)(-1)) {
+        delete pathdup;
+        return -1;
+    }
+    u_int64_t target_inode = 0;
+
+    // remove its record from parent
+    INode parent_INode;
+    parent_INode.inode_construct(parent_inode, disk);
+    char rw_buffer[IO_BLOCK_SIZE] = {0};
+    for (u_int64_t idx=0; idx<parent_INode.size; idx++) {
+        read_datablock(parent_INode, idx, rw_buffer);
+        DirectoryEntry ent;
+        for(int i=0;i<=IO_BLOCK_SIZE-64;i+=64){
+            ent.deserialize(rw_buffer+i);
+            if (strcmp(ent.file_name, filename)==0) {
+                target_inode = ent.inode_number;
+                ent.inode_number = 0;
+                ent.serialize(rw_buffer+i);
+                break;
+            }
+        }
+        if (target_inode) {
+            write_datablock(parent_INode, idx, rw_buffer);
+            break;
+        }
+    }
+    
+    // remove inode itself
+    if (target_inode) {
+        unlink_inode(target_inode);
+        delete pathdup;
+        return 0;
+    } else {
+        printf("cannot find %s in %s", filename, ParentPath);
+        delete pathdup;
+        return -1;
+    }
 }
\ No newline at end of file
diff --git a/test/layer2_API.cpp b/test/layer2_API.cpp
index 164b632..8282ae3 100644
--- a/test/layer2_API.cpp
+++ b/test/layer2_API.cpp
@@ -80,7 +80,7 @@ int main(int argc, char *argv[]) {
     printf("=== Part 5: pressure test create files ===\n");
     u_int64_t file_pressure = fsop.fischl_mkdir("/pressure", 0);
     u_int64_t inode_numbers[700];
-    std::string prefix = "/pressure/";
+    std::string prefix = "/pressure/No_";
     for(int i=0;i<700;i++){
         inode_numbers[i] = fsop.fischl_mkdir((prefix+std::to_string(i)).c_str(), 0);
     }
@@ -88,4 +88,18 @@ int main(int argc, char *argv[]) {
         u_int64_t inode_number = fsop.namei((prefix+std::to_string(i)).c_str());
         assert(inode_number == inode_numbers[i]);
     }
+
+    printf("=== Part 6: unlink test ===\n");
+    fsop.printDirectory(file_pressure);
+    for(int i=0;i<700;i+=2){
+        assert(!fsop.fischl_unlink((prefix+std::to_string(i)).c_str()));
+    }
+    for(int i=0;i<4;i+=2){
+        assert(fsop.namei((prefix+std::to_string(i)).c_str())==(u_int64_t)(-1));
+    }
+    for(int i=1;i<700;i+=2){
+        u_int64_t inode_number = fsop.namei((prefix+std::to_string(i)).c_str());
+        assert(inode_number == inode_numbers[i]);
+    }
+    fsop.printDirectory(file_pressure);
 }
\ No newline at end of file