1MKNOD(2)                   Linux Programmer's Manual                  MKNOD(2)
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NAME

6       mknod, mknodat - create a special or ordinary file
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SYNOPSIS

9       #include <sys/stat.h>
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11       int mknod(const char *pathname, mode_t mode, dev_t dev);
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13       #include <fcntl.h>           /* Definition of AT_* constants */
14       #include <sys/stat.h>
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16       int mknodat(int dirfd, const char *pathname, mode_t mode, dev_t dev);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       mknod():
21           _XOPEN_SOURCE >= 500
22               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

26       The system call mknod() creates a filesystem node (file, device special
27       file, or named pipe) named pathname, with attributes specified by  mode
28       and dev.
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30       The  mode  argument specifies both the file mode to use and the type of
31       node to be created.  It should be a combination (using bitwise  OR)  of
32       one  of  the  file types listed below and zero or more of the file mode
33       bits listed in inode(7).
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35       The file mode is modified by the process's umask in the usual  way:  in
36       the  absence  of a default ACL, the permissions of the created node are
37       (mode & ~umask).
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39       The file type must be one of S_IFREG,  S_IFCHR,  S_IFBLK,  S_IFIFO,  or
40       S_IFSOCK to specify a regular file (which will be created empty), char‐
41       acter special file, block special file, FIFO (named pipe), or UNIX  do‐
42       main  socket,  respectively.   (Zero  file  type  is equivalent to type
43       S_IFREG.)
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45       If the file type is S_IFCHR or S_IFBLK, then dev  specifies  the  major
46       and  minor numbers of the newly created device special file (makedev(3)
47       may be useful to build the value for dev); otherwise it is ignored.
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49       If pathname already exists, or is a symbolic link, this call fails with
50       an EEXIST error.
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52       The  newly  created  node will be owned by the effective user ID of the
53       process.  If the directory containing the node has the set-group-ID bit
54       set,  or if the filesystem is mounted with BSD group semantics, the new
55       node will inherit the group ownership from its parent directory; other‐
56       wise it will be owned by the effective group ID of the process.
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58   mknodat()
59       The  mknodat() system call operates in exactly the same way as mknod(),
60       except for the differences described here.
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62       If the pathname given in pathname is relative, then it  is  interpreted
63       relative  to  the  directory  referred  to by the file descriptor dirfd
64       (rather than relative to the current working directory of  the  calling
65       process, as is done by mknod() for a relative pathname).
66
67       If  pathname  is relative and dirfd is the special value AT_FDCWD, then
68       pathname is interpreted relative to the current  working  directory  of
69       the calling process (like mknod()).
70
71       If pathname is absolute, then dirfd is ignored.
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73       See openat(2) for an explanation of the need for mknodat().
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RETURN VALUE

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

80       EACCES The parent directory does not  allow  write  permission  to  the
81              process,  or  one of the directories in the path prefix of path‐
82              name did not allow search permission.   (See  also  path_resolu‐
83              tion(7).)
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85       EBADF  (mknodat())  pathname  is relative but dirfd is neither AT_FDCWD
86              nor a valid file descriptor.
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88       EDQUOT The user's quota of disk blocks or inodes on the filesystem  has
89              been exhausted.
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91       EEXIST pathname  already exists.  This includes the case where pathname
92              is a symbolic link, dangling or not.
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94       EFAULT pathname points outside your accessible address space.
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96       EINVAL mode requested creation of something other than a regular  file,
97              device special file, FIFO or socket.
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99       ELOOP  Too many symbolic links were encountered in resolving pathname.
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101       ENAMETOOLONG
102              pathname was too long.
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104       ENOENT A  directory  component  in pathname does not exist or is a dan‐
105              gling symbolic link.
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107       ENOMEM Insufficient kernel memory was available.
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109       ENOSPC The device containing pathname has no room for the new node.
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111       ENOTDIR
112              A component used as a directory in pathname is not, in  fact,  a
113              directory.
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115       ENOTDIR
116              (mknodat())  pathname is relative and dirfd is a file descriptor
117              referring to a file other than a directory.
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119       EPERM  mode requested creation of something other than a regular  file,
120              FIFO  (named pipe), or UNIX domain socket, and the caller is not
121              privileged (Linux: does not have the CAP_MKNOD capability); also
122              returned  if the filesystem containing pathname does not support
123              the type of node requested.
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125       EROFS  pathname refers to a file on a read-only filesystem.
126

VERSIONS

128       mknodat() was added to Linux in  kernel  2.6.16;  library  support  was
129       added to glibc in version 2.4.
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CONFORMING TO

132       mknod(): SVr4, 4.4BSD, POSIX.1-2001 (but see below), POSIX.1-2008.
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134       mknodat(): POSIX.1-2008.
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NOTES

137       POSIX.1-2001  says:  "The  only  portable use of mknod() is to create a
138       FIFO-special file.  If mode is not S_IFIFO or dev is not 0, the  behav‐
139       ior of mknod() is unspecified."  However, nowadays one should never use
140       mknod() for this purpose; one should use mkfifo(3),  a  function  espe‐
141       cially defined for this purpose.
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143       Under  Linux, mknod() cannot be used to create directories.  One should
144       make directories with mkdir(2).
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146       There are many infelicities in the protocol underlying  NFS.   Some  of
147       these affect mknod() and mknodat().
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SEE ALSO

150       mknod(1),  chmod(2), chown(2), fcntl(2), mkdir(2), mount(2), socket(2),
151       stat(2), umask(2), unlink(2), makedev(3), mkfifo(3), acl(5), path_reso‐
152       lution(7)
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COLOPHON

155       This  page  is  part of release 5.13 of the Linux man-pages project.  A
156       description of the project, information about reporting bugs,  and  the
157       latest     version     of     this    page,    can    be    found    at
158       https://www.kernel.org/doc/man-pages/.
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162Linux                             2021-08-27                          MKNOD(2)
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