mkdirat函數

LINUX apue 裡介紹檔案夾的建立時使用了mkdir() 和 mkdirat()。我常用的是前者，而mkdirat則需要目标檔案夾的檔案描述符。 

man 2 mkdir

NAME

mkdir, mkdirat - create a directory

      

SYNOPSIS

#include <sys/stat.h>
       #include <sys/types.h>

       int mkdir(const char *pathname, mode_t mode);

       #include <fcntl.h>           /* Definition of AT_* constants */
       #include <sys/stat.h>

       int mkdirat(int dirfd, const char *pathname, mode_t mode);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       mkdirat():
           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _ATFILE_SOURCE

      

DESCRIPTION

mkdir() attempts to create a directory named pathname.

       The  argument  mode  specifies  the  mode  for  the  new directory (see
       stat(2)).  It is modified by the process's umask in the usual  way:  in
       the  absence  of  a  default  ACL, the mode of the created directory is
       (mode & ~umask & 0777).  Whether other mode bits are  honored  for  the
       created  directory  depends  on  the  operating system.  For Linux, see
       NOTES below.

       The newly created directory will be owned by the effective user  ID  of
       the process.  If the directory containing the file has the set-group-ID
       bit set, or if the filesystem  is  mounted  with  BSD  group  semantics
       (mount -o bsdgroups or, synonymously mount -o grpid), the new directory
       will inherit the group ownership from its parent; otherwise it will  be
       owned by the effective group ID of the process.

       If  the parent directory has the set-group-ID bit set, then so will the
       newly created directory.

   mkdirat()
       The mkdirat() system call operates in exactly the same way as  mkdir(),
       except for the differences described here.

       If  the  pathname given in pathname is relative, then it is interpreted
       relative to the directory referred to  by  the  file  descriptor  dirfd
       (rather  than  relative to the current working directory of the calling
       process, as is done by mkdir() for a relative pathname).

       If pathname is relative and dirfd is the special value  AT_FDCWD,  then
       pathname  is  interpreted  relative to the current working directory of
       the calling process (like mkdir()).

       If pathname is absolute, then dirfd is ignored.

       See openat(2) for an explanation of the need for mkdirat().

      

RETURN VALUE

mkdir() and mkdirat() return  zero  on  success,  or  -1  if  an  error
       occurred (in which case, errno is set appropriately).

      

ERRORS

EACCES The  parent  directory  does  not  allow write permission to the
              process, or one of the directories in  pathname  did  not  allow
              search permission.  (See also path_resolution(7).)

       EDQUOT The  user's quota of disk blocks or inodes on the filesystem has
              been exhausted.

       EEXIST pathname already exists (not necessarily as a directory).   This
              includes the case where pathname is a symbolic link, dangling or
              not.

       EFAULT pathname points outside your accessible address space.

       ELOOP  Too many symbolic links were encountered in resolving pathname.

       EMLINK The number  of  links  to  the  parent  directory  would  exceed
              LINK_MAX.

       ENAMETOOLONG
              pathname was too long.

       ENOENT A  directory  component  in  pathname  does  not  exist  or is a
              dangling symbolic link.

       ENOMEM Insufficient kernel memory was available.

       ENOSPC The  device  containing  pathname  has  no  room  for  the   new
              directory.

       ENOSPC The  new  directory  cannot  be  created because the user's disk
              quota is exhausted.

       ENOTDIR
              A component used as a directory in pathname is not, in  fact,  a
              directory.

       EPERM  The filesystem containing pathname does not support the creation
              of directories.

       EROFS  pathname refers to a file on a read-only filesystem.

       The following additional errors can occur for mkdirat():

       EBADF  dirfd is not a valid file descriptor.

       ENOTDIR
              pathname is relative and dirfd is a file descriptor referring to
              a file other than a directory.

      

VERSIONS

mkdirat()  was  added  to  Linux  in kernel 2.6.16; library support was
       added to glibc in version 2.4.

      

CONFORMING TO

mkdir(): SVr4, BSD, POSIX.1-2001, POSIX.1-2008.

       mkdirat(): POSIX.1-2008.

      

NOTES

Under Linux, apart from the permission bits, the S_ISVTX  mode  bit  is
       also honored.

       There  are  many  infelicities in the protocol underlying NFS.  Some of
       these affect mkdir().

   Glibc notes
       On older kernels where mkdirat()  is  unavailable,  the  glibc  wrapper
       function falls back to the use of mkdir().  When pathname is a relative
       pathname, glibc constructs a pathname based on  the  symbolic  link  in
       /proc/self/fd that corresponds to the dirfd argument.

      

SEE ALSO

mkdir(1),  chmod(2),  chown(2),  mknod(2), mount(2), rmdir(2), stat(2),
       umask(2), unlink(2), acl(5) path_resolution(7)

      

COLOPHON

This page is part of release 4.04 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       http://www.kernel.org/doc/man-pages/.      

#include <stdio.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <string.h>

#include <time.h>

#include <dirent.h>

#include <unistd.h> // for close

int main(void)

{

    //struct dirent *dirp;

    DIR *dp;

    if(NULL == (dp = opendir(".")))

    {

        return -1;

    }

    int fd = dirfd(dp);

    if(fd < 0)

    {

        return -1;

    }

    //mkdir("abc", 0777);

    mkdirat(fd, "abc", 0777);

    //mkdirat(fd, "abcd", 0777);

    closedir(dp);

    return 0;

//不知道有沒有少什麼

}

http://blog.csdn.net/zhuyi2654715/article/details/7605051

https://www.cnblogs.com/aaronLinux/p/5617070.html

http://blog.csdn.net/ffjffjffjffjffj/article/details/78056238