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28.\"     @(#)mknod.2	8.1 (Berkeley) 6/4/93
29.\" $FreeBSD: stable/12/lib/libc/sys/mknod.2 365473 2020-09-08 20:51:19Z jhb $
30.\"
31.Dd March 30, 2020
32.Dt MKNOD 2
33.Os
34.Sh NAME
35.Nm mknod ,
36.Nm mknodat
37.Nd make a special file node
38.Sh LIBRARY
39.Lb libc
40.Sh SYNOPSIS
41.In sys/stat.h
42.Ft int
43.Fn mknod "const char *path" "mode_t mode" "dev_t dev"
44.Ft int
45.Fn mknodat "int fd" "const char *path" "mode_t mode" "dev_t dev"
46.Sh DESCRIPTION
47The file system node
48.Fa path
49is created with the file type and access permissions specified in
50.Fa mode .
51The access permissions are modified by the process's umask value.
52.Pp
53If
54.Fa mode
55indicates a block or character special file,
56.Fa dev
57is a configuration dependent specification denoting a particular device
58on the system.
59Otherwise,
60.Fa dev
61is ignored.
62.Pp
63The
64.Fn mknod
65system call
66requires super-user privileges.
67.Pp
68The
69.Fn mknodat
70system call is equivalent to
71.Fn mknod
72except in the case where
73.Fa path
74specifies a relative path.
75In this case the newly created device node is created relative to the
76directory associated with the file descriptor
77.Fa fd
78instead of the current working directory.
79If
80.Fn mknodat
81is passed the special value
82.Dv AT_FDCWD
83in the
84.Fa fd
85parameter, the current working directory is used and the behavior is
86identical to a call to
87.Fn mknod .
88.Sh RETURN VALUES
89.Rv -std mknod
90.Sh ERRORS
91The
92.Fn mknod
93system call
94will fail and the file will be not created if:
95.Bl -tag -width Er
96.It Bq Er ENOTDIR
97A component of the path prefix is not a directory.
98.It Bq Er ENAMETOOLONG
99A component of a pathname exceeded 255 characters,
100or an entire path name exceeded 1023 characters.
101.It Bq Er ENOENT
102A component of the path prefix does not exist.
103.It Bq Er EACCES
104Search permission is denied for a component of the path prefix.
105.It Bq Er ELOOP
106Too many symbolic links were encountered in translating the pathname.
107.It Bq Er EPERM
108The process's effective user ID is not super-user.
109.It Bq Er EIO
110An I/O error occurred while making the directory entry or allocating the inode.
111.It Bq Er EINTEGRITY
112Corrupted data was detected while reading from the file system.
113.It Bq Er ENOSPC
114The directory in which the entry for the new node is being placed
115cannot be extended because there is no space left on the file
116system containing the directory.
117.It Bq Er ENOSPC
118There are no free inodes on the file system on which the
119node is being created.
120.It Bq Er EDQUOT
121The directory in which the entry for the new node
122is being placed cannot be extended because the
123user's quota of disk blocks on the file system
124containing the directory has been exhausted.
125.It Bq Er EDQUOT
126The user's quota of inodes on the file system on
127which the node is being created has been exhausted.
128.It Bq Er EROFS
129The named file resides on a read-only file system.
130.It Bq Er EEXIST
131The named file exists.
132.It Bq Er EFAULT
133The
134.Fa path
135argument
136points outside the process's allocated address space.
137.It Bq Er EINVAL
138Creating anything else than a block or character special
139file (or a
140.Em whiteout )
141is not supported.
142.El
143.Pp
144In addition to the errors returned by the
145.Fn mknod ,
146the
147.Fn mknodat
148may fail if:
149.Bl -tag -width Er
150.It Bq Er EBADF
151The
152.Fa path
153argument does not specify an absolute path and the
154.Fa fd
155argument is neither
156.Dv AT_FDCWD
157nor a valid file descriptor open for searching.
158.It Bq Er ENOTDIR
159The
160.Fa path
161argument is not an absolute path and
162.Fa fd
163is neither
164.Dv AT_FDCWD
165nor a file descriptor associated with a directory.
166.El
167.Sh SEE ALSO
168.Xr chmod 2 ,
169.Xr mkfifo 2 ,
170.Xr stat 2 ,
171.Xr umask 2
172.Sh STANDARDS
173The
174.Fn mknodat
175system call follows The Open Group Extended API Set 2 specification.
176.Sh HISTORY
177The
178.Fn mknod
179function appeared in
180.At v4 .
181The
182.Fn mknodat
183system call appeared in
184.Fx 8.0 .
185