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

6       mknod, mknodat - create a special or ordinary file
7

SYNOPSIS

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

29       The system call mknod() creates a filesystem node (file, device special
30       file, or named pipe) named pathname, with attributes specified by  mode
31       and dev.
32
33       The  mode  argument specifies both the file mode to use and the type of
34       node to be created.  It should be a combination (using bitwise  OR)  of
35       one  of  the  file types listed below and zero or more of the file mode
36       bits listed in inode(7).
37
38       The file mode is modified by the process's umask in the usual  way:  in
39       the  absence  of a default ACL, the permissions of the created node are
40       (mode & ~umask).
41
42       The file type must be one of S_IFREG,  S_IFCHR,  S_IFBLK,  S_IFIFO,  or
43       S_IFSOCK to specify a regular file (which will be created empty), char‐
44       acter special file, block special file,  FIFO  (named  pipe),  or  UNIX
45       domain  socket,  respectively.   (Zero  file type is equivalent to type
46       S_IFREG.)
47
48       If the file type is S_IFCHR or S_IFBLK, then dev  specifies  the  major
49       and  minor numbers of the newly created device special file (makedev(3)
50       may be useful to build the value for dev); otherwise it is ignored.
51
52       If pathname already exists, or is a symbolic link, this call fails with
53       an EEXIST error.
54
55       The  newly  created  node will be owned by the effective user ID of the
56       process.  If the directory containing the node has the set-group-ID bit
57       set,  or if the filesystem is mounted with BSD group semantics, the new
58       node will inherit the group ownership from its parent directory; other‐
59       wise it will be owned by the effective group ID of the process.
60
61   mknodat()
62       The  mknodat() system call operates in exactly the same way as mknod(),
63       except for the differences described here.
64
65       If the pathname given in pathname is relative, then it  is  interpreted
66       relative  to  the  directory  referred  to by the file descriptor dirfd
67       (rather than relative to the current working directory of  the  calling
68       process, as is done by mknod() for a relative pathname).
69
70       If  pathname  is relative and dirfd is the special value AT_FDCWD, then
71       pathname is interpreted relative to the current  working  directory  of
72       the calling process (like mknod()).
73
74       If pathname is absolute, then dirfd is ignored.
75
76       See openat(2) for an explanation of the need for mknodat().
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RETURN VALUE

79       mknod()  and  mknodat()  return  zero  on  success,  or  -1 if an error
80       occurred (in which case, errno is set appropriately).
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ERRORS

83       EACCES The parent directory does not  allow  write  permission  to  the
84              process,  or  one of the directories in the path prefix of path‐
85              name did not allow search permission.   (See  also  path_resolu‐
86              tion(7).)
87
88       EDQUOT The  user's quota of disk blocks or inodes on the filesystem has
89              been exhausted.
90
91       EEXIST pathname already exists.  This includes the case where  pathname
92              is a symbolic link, dangling or not.
93
94       EFAULT pathname points outside your accessible address space.
95
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.
114
115       EPERM  mode requested creation of something other than a regular  file,
116              FIFO  (named pipe), or UNIX domain socket, and the caller is not
117              privileged (Linux: does not have the CAP_MKNOD capability); also
118              returned  if the filesystem containing pathname does not support
119              the type of node requested.
120
121       EROFS  pathname refers to a file on a read-only filesystem.
122
123       The following additional errors can occur for mknodat():
124
125       EBADF  dirfd is not a valid file descriptor.
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127       ENOTDIR
128              pathname is relative and dirfd is a file descriptor referring to
129              a file other than a directory.
130

VERSIONS

132       mknodat()  was  added  to  Linux  in kernel 2.6.16; library support was
133       added to glibc in version 2.4.
134

CONFORMING TO

136       mknod(): SVr4, 4.4BSD, POSIX.1-2001 (but see below), POSIX.1-2008.
137
138       mknodat(): POSIX.1-2008.
139

NOTES

141       POSIX.1-2001 says: "The only portable use of mknod()  is  to  create  a
142       FIFO-special  file.  If mode is not S_IFIFO or dev is not 0, the behav‐
143       ior of mknod() is unspecified."  However, nowadays one should never use
144       mknod()  for  this  purpose; one should use mkfifo(3), a function espe‐
145       cially defined for this purpose.
146
147       Under Linux, mknod() cannot be used to create directories.  One  should
148       make directories with mkdir(2).
149
150       There  are  many  infelicities in the protocol underlying NFS.  Some of
151       these affect mknod() and mknodat().
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SEE ALSO

154       mknod(1), chmod(2), chown(2), fcntl(2), mkdir(2), mount(2),  socket(2),
155       stat(2),  umask(2), unlink(2), makedev(3), mkfifo(3), acl(5) path_reso‐
156       lution(7)
157

COLOPHON

159       This page is part of release 4.15 of the Linux  man-pages  project.   A
160       description  of  the project, information about reporting bugs, and the
161       latest    version    of    this    page,    can     be     found     at
162       https://www.kernel.org/doc/man-pages/.
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166Linux                             2017-09-15                          MKNOD(2)
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