diff --git a/4/fileDirectory/.dirent.c.swp b/4/fileDirectory/.dirent.c.swp
new file mode 100644
index 0000000..65e0b12
Binary files /dev/null and b/4/fileDirectory/.dirent.c.swp differ
diff --git a/4/fileDirectory/.filetime.c.swp b/4/fileDirectory/.filetime.c.swp
new file mode 100644
index 0000000..d1733e3
Binary files /dev/null and b/4/fileDirectory/.filetime.c.swp differ
diff --git a/4/fileDirectory/.mkdir.c.swp b/4/fileDirectory/.mkdir.c.swp
new file mode 100644
index 0000000..37480d0
Binary files /dev/null and b/4/fileDirectory/.mkdir.c.swp differ
diff --git a/4/fileDirectory/access.c b/4/fileDirectory/access.c
new file mode 100644
index 0000000..037375e
--- /dev/null
+++ b/4/fileDirectory/access.c
@@ -0,0 +1,19 @@
+#include <unistd.h>
+#include <stdio.h>
+
+int main(void){
+  if(access("./access.c", R_OK | W_OK) < 0){
+    printf("access error for acccess.c\n");
+  }
+  else {
+    printf("read and write access OK\n");
+  }
+
+  if(access("./access.c", R_OK | X_OK) < 0){
+    printf("access error for acccess.c\n");
+  }
+  else {
+    printf("exec access OK\n");
+  }
+  return 0;
+}
diff --git a/4/fileDirectory/chdir.c b/4/fileDirectory/chdir.c
new file mode 100644
index 0000000..0eeaf73
--- /dev/null
+++ b/4/fileDirectory/chdir.c
@@ -0,0 +1,6 @@
+#include <unistd.h>
+
+int main(void) {
+  // TODO
+  return 0;
+}
diff --git a/4/fileDirectory/chmod.c b/4/fileDirectory/chmod.c
new file mode 100644
index 0000000..f37ea6f
--- /dev/null
+++ b/4/fileDirectory/chmod.c
@@ -0,0 +1,22 @@
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#define RWRWRW S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH
+#define RWRR S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH
+
+int main(void){
+  int fd = open("./test/test2", O_RDWR);
+  if(fd == -1){
+    printf("open file test1 error\n");
+  }
+  
+  fchmod(fd, RWRWRW);
+
+  close(fd);
+
+  chmod("./test/test1", RWRR);
+
+  return 0;
+}
diff --git a/4/fileDirectory/chown.c b/4/fileDirectory/chown.c
new file mode 100644
index 0000000..f86e3d7
--- /dev/null
+++ b/4/fileDirectory/chown.c
@@ -0,0 +1,8 @@
+#include <unistd.h>
+#include <limits.h>
+#include <stdio.h>
+
+int main(void){
+  printf("%ld\n", pathconf("./chown.c",_POSIX_CHOWN_RESTRICTED));
+  return 0;
+}
diff --git a/4/fileDirectory/dirent.c b/4/fileDirectory/dirent.c
new file mode 100644
index 0000000..b2a9c4f
--- /dev/null
+++ b/4/fileDirectory/dirent.c
@@ -0,0 +1,23 @@
+#include <dirent.h>
+#include <stdio.h>
+
+int main(void) {
+  DIR *pdir = opendir(".");
+
+  if(pdir == NULL) {
+    printf("opendir error\n");
+    return -1;
+  }
+
+ struct dirent *pdirent = NULL;
+  
+ while((pdirent = readdir(pdir)) != NULL){
+   long index = telldir(pdir);
+   printf("%15s %18ld %lu\n", pdirent->d_name, index, pdirent->d_ino);
+
+ }
+
+ closedir(pdir);
+
+  return 0;
+}
diff --git a/4/fileDirectory/filetime.c b/4/fileDirectory/filetime.c
new file mode 100644
index 0000000..e10d239
--- /dev/null
+++ b/4/fileDirectory/filetime.c
@@ -0,0 +1,52 @@
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdio.h>
+
+
+int main(void) {
+  int fd = open("./filetime.c", O_RDWR);
+  
+  if(fd == -1) {
+    printf("open file eror filetime.c\n");
+    return -1;
+  }
+
+  
+  struct stat buf;
+
+  if(fstat(fd, &buf) < 0){
+    printf("stat error\n");
+    return -1;
+  }
+
+  struct timespec atim = buf.st_atim,
+                  ctim = buf.st_ctim, 
+                  mtim = buf.st_mtim;
+
+  printf("sec  time: %12ld %12ld %12ld\n", atim.tv_sec, ctim.tv_sec, mtim.tv_sec);
+  printf("nsec time: %12ld %12ld %12ld\n", atim.tv_nsec, ctim.tv_nsec, mtim.tv_nsec);
+
+  int fd1 = open("./test/test3", O_RDWR);
+
+  if(fd1 == -1) {
+    printf("open file error test3\n");
+    return -1;
+  }
+
+  struct timespec times[2];
+
+  times[0] = atim;
+  times[1] = ctim;
+
+  if(futimens(fd1, times) < 0) {
+    printf("futimens error\n");
+    return -1;
+  }
+
+  close(fd1);
+
+  close(fd);
+
+  return 0;
+}
diff --git a/4/fileDirectory/links.c b/4/fileDirectory/links.c
new file mode 100644
index 0000000..e9cd9a2
--- /dev/null
+++ b/4/fileDirectory/links.c
@@ -0,0 +1,60 @@
+#include <errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+
+extern int errno;
+
+int main(void) {
+  int fd = open("./links.c", O_RDWR);
+
+  if(fd == -1) {
+    printf("oprn error test1\n");
+    return -1;
+  }
+  
+  struct stat buf;
+
+  if(fstat(fd, &buf) < 0) {
+    printf("fstat error\n");
+    return -1;
+  }
+
+  printf("%lu\n", buf.st_nlink);
+
+  close(fd);
+
+  fd = open(".", O_RDONLY);
+
+  if(fd == -1){
+    printf("open error .\n");
+    return -1;
+  }
+
+  int fd2 = open("/home/eric", O_RDONLY);
+
+  if(fd2 == -1){
+    printf("open error ~\n");
+    return -1;
+  }
+  
+  if(linkat(fd, "links.c", fd2, "test/linksl.c", 0) < 0) {
+    printf("linkat error\n");
+    if(errno != 0) {
+      printf("strerr: %s\n", strerror(errno)); 
+    }
+  }
+
+  if(unlinkat(fd2, "test/linksl.c", 0) < 0) {
+    printf("unlinkat error\n");
+    return -1;
+  }
+
+  close(fd);
+  close(fd2);
+
+
+  return 0;
+}
diff --git a/4/fileDirectory/mkdir.c b/4/fileDirectory/mkdir.c
new file mode 100644
index 0000000..bf92f77
--- /dev/null
+++ b/4/fileDirectory/mkdir.c
@@ -0,0 +1,18 @@
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#define RWXRR S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IROTH
+
+int main(void) {
+  if(mkdir("/home/eric/test/testmkdir", RWXRR) < 0) {
+    printf("mkdir error\n");
+  }
+
+  if(rmdir("/home/eric/test/testmkdir") < 0) {
+    printf("rmdir error\n");
+    return -1;
+  }
+  
+  return 0;
+}
diff --git a/4/fileDirectory/rename.c b/4/fileDirectory/rename.c
new file mode 100644
index 0000000..3eaa34b
--- /dev/null
+++ b/4/fileDirectory/rename.c
@@ -0,0 +1,10 @@
+#include <fcntl.h>
+#include <stdio.h>
+
+int main(void) {
+  if(renameat(AT_FDCWD, "test/test2", AT_FDCWD, "test/test3") < 0) {
+    printf("rename error\n");
+    return -1;
+  }
+  return 0;
+}
diff --git a/4/fileDirectory/stat.c b/4/fileDirectory/stat.c
new file mode 100644
index 0000000..21b5d87
--- /dev/null
+++ b/4/fileDirectory/stat.c
@@ -0,0 +1,45 @@
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int printStat(struct stat buf){
+
+  printf("DEV: %ld UID: %d SIZE: %ld BLOCKS: %ld\n", buf.st_dev, buf.st_uid, buf.st_size, buf.st_blocks);
+  printf("MODE: %d INO: %ld BLKSIZE: %ld GID: %d\n", buf.st_mode, buf.st_ino, buf.st_blksize, buf.st_gid);
+
+  if(S_ISREG(buf.st_mode)){
+    printf("a regular file\n");
+  } 
+  else if(S_ISDIR(buf.st_mode)) {
+    printf("a directory\n");
+  }
+}
+
+int main(void){
+  struct stat buf;
+  if(stat("./stat.c", &buf) == -1){
+    printf("stat error\n");
+    return -1;
+  }
+  
+  printStat(buf);
+
+  int fd = open(".", O_RDONLY);
+
+  if(fd == -1){
+    printf("open O_RDONLY failed\n");
+    return -1;
+  }
+
+  if(fstat(fd, &buf) < 0){
+    printf("fstat error\n");
+    return -1;
+  }
+
+  printStat(buf);
+
+  close(fd);
+
+  return 0;
+}
diff --git a/4/fileDirectory/symlinks.c b/4/fileDirectory/symlinks.c
new file mode 100644
index 0000000..dda2ebb
--- /dev/null
+++ b/4/fileDirectory/symlinks.c
@@ -0,0 +1,34 @@
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+int main(void) {
+  
+  int fd = open("/home/eric", O_RDONLY);
+
+  if(fd == -1) {
+    printf("open error for directory .\n");
+    return -1;
+  }
+
+  if(symlinkat("symlinks.c", fd, "test/symlinksl.c") < 0) {
+    printf("symlink error\n");
+    return -1;
+  }
+
+  close(fd);
+
+  char buf[1024];
+  ssize_t rbit = readlink("/home/eric/test/symlinksl.c", buf, 1024);
+
+  if(rbit < 0) {
+    printf("readlink error\n");
+    return -1;
+  }
+
+  buf[rbit] = 0;
+
+  printf("rbit: %d buf: %s\n", rbit, buf);
+
+  return 0;
+}
diff --git a/4/fileDirectory/test/test1 b/4/fileDirectory/test/test1
new file mode 100644
index 0000000..65f57c2
Binary files /dev/null and b/4/fileDirectory/test/test1 differ
diff --git a/4/fileDirectory/test/test3 b/4/fileDirectory/test/test3
new file mode 100644
index 0000000..e69de29
diff --git a/4/fileDirectory/trunc.c b/4/fileDirectory/trunc.c
new file mode 100644
index 0000000..33b6a93
--- /dev/null
+++ b/4/fileDirectory/trunc.c
@@ -0,0 +1,9 @@
+#include <unistd.h>
+#include <stdio.h>
+
+int main(void){
+  if(truncate("./test/test1", 256) < 0) {
+    printf("truncate error for file test1\n");
+  }
+  return 0;
+}
diff --git a/4/fileDirectory/umask.c b/4/fileDirectory/umask.c
new file mode 100644
index 0000000..d34db96
--- /dev/null
+++ b/4/fileDirectory/umask.c
@@ -0,0 +1,17 @@
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+#define RWRWRW S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH
+
+int main(void) {
+  umask(0);
+  if(creat("./test/test1", RWRWRW) < 0){
+    printf("creat error for test1\n");
+  }
+  umask(S_IWGRP | S_IROTH  | S_IWOTH);
+
+  if(creat("./test/test2", RWRWRW) < 0){
+    printf("creat error for test1\n");
+  }
+}