noble (2) mknod.2.gz

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NAME

       mknod, mknodat - create a special or ordinary file

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/stat.h>

       int mknod(const char *pathname, mode_t mode, dev_t dev);

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

       int mknodat(int dirfd, const char *pathname, mode_t mode, dev_t dev);

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

       mknod():
           _XOPEN_SOURCE >= 500
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

       The  system  call  mknod()  creates  a  filesystem  node (file, device special file, or named pipe) named
       pathname, with attributes specified by mode and dev.

       The mode argument specifies both the file mode to use and the type of node to be created.  It should be a
       combination  (using  bitwise  OR) of one of the file types listed below and zero or more of the file mode
       bits listed in inode(7).

       The file mode is modified by the process's umask in the usual way: in the absence of a default  ACL,  the
       permissions of the created node are (mode & ~umask).

       The  file  type  must be one of S_IFREG, S_IFCHR, S_IFBLK, S_IFIFO, or S_IFSOCK to specify a regular file
       (which will be created empty), character special file, block special file, FIFO  (named  pipe),  or  UNIX
       domain socket, respectively.  (Zero file type is equivalent to type S_IFREG.)

       If  the  file  type  is  S_IFCHR  or S_IFBLK, then dev specifies the major and minor numbers of the newly
       created device special file (makedev(3) may be useful to build  the  value  for  dev);  otherwise  it  is
       ignored.

       If pathname already exists, or is a symbolic link, this call fails with an EEXIST error.

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

   mknodat()
       The mknodat() system call operates in exactly the  same  way  as  mknod(),  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 mknod() 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 mknod()).

       If pathname is absolute, then dirfd is ignored.

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

RETURN VALUE

       mknod() and mknodat() return zero on success.  On error, -1 is returned and errno is set to indicate  the
       error.

ERRORS

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

       EBADF  (mknodat()) pathname is relative but dirfd is neither AT_FDCWD nor a valid file descriptor.

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

       EEXIST pathname already exists.  This includes the case where pathname is a symbolic  link,  dangling  or
              not.

       EFAULT pathname points outside your accessible address space.

       EINVAL mode  requested  creation  of  something  other  than a regular file, device special file, FIFO or
              socket.

       ELOOP  Too many symbolic links were encountered in resolving pathname.

       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 node.

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

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

       EPERM  mode  requested creation of something other than a regular file, FIFO (named pipe), or UNIX domain
              socket, and the caller is not privileged (Linux: does not have  the  CAP_MKNOD  capability);  also
              returned if the filesystem containing pathname does not support the type of node requested.

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

VERSIONS

       POSIX.1-2001  says:  "The  only portable use of mknod() is to create a FIFO-special file.  If mode is not
       S_IFIFO or dev is not 0, the behavior of mknod() is unspecified."  However, nowadays one should never use
       mknod() for this purpose; one should use mkfifo(3), a function especially defined for this purpose.

       Under Linux, mknod() cannot be used to create directories.  One should make directories with mkdir(2).

STANDARDS

       POSIX.1-2008.

HISTORY

       mknod()
              SVr4, 4.4BSD, POSIX.1-2001 (but see VERSIONS).

       mknodat()
              Linux 2.6.16, glibc 2.4.  POSIX.1-2008.

NOTES

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

SEE ALSO

       mknod(1),  chmod(2),  chown(2),  fcntl(2),  mkdir(2),  mount(2), socket(2), stat(2), umask(2), unlink(2),
       makedev(3), mkfifo(3), acl(5), path_resolution(7)