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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON |
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mknod(2) System Calls Manual mknod(2)
mknod, mknodat - create a special or ordinary file
Standard C library (libc, -lc)
#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
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().
mknod() and mknodat() return zero on success. On error, -1 is
returned and errno is set to indicate the error.
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.
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).
POSIX.1-2008.
mknod()
SVr4, 4.4BSD, POSIX.1-2001 (but see VERSIONS).
mknodat()
Linux 2.6.16, glibc 2.4. POSIX.1-2008.
There are many infelicities in the protocol underlying NFS. Some
of these affect mknod() and mknodat().
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)
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for this manual page, see
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version of the page, or you believe there is a better or more up-
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man-pages@man7.org
Linux man-pages 6.9.1 2024-05-02 mknod(2)
Pages that refer to this page: mknod(1), fcntl(2), mkdir(2), open(2), syscalls(2), unlink(2), dev_t(3type), makedev(3), mkfifo(3), remove(3), intro(4), fstab(5), proc_pid_attr(5), capabilities(7), inode(7), signal-safety(7), mount(8), xfs_db(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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