mknod(3) - Linux man page

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Name

mknod - make a directory, a special file, or a regular file

Synopsis

#include <sys/stat.h>

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

Description

The mknod() function shall create a new file named by the pathname to which the argument path points.

The file type for path is OR'ed into the mode argument, and the application shall select one of the following symbolic constants:

S_ISGID	Set group ID on execution.
S_IRWXU	Read, write, or execute (search) by owner.
S_IRUSR	Read by owner.
S_IWUSR	Write by owner.
S_IXUSR	Execute (search) by owner.
S_IRWXG	Read, write, or execute (search) by group.
S_IRGRP	Read by group.
S_IWGRP	Write by group.
S_IXGRP	Execute (search) by group.
S_IRWXO	Read, write, or execute (search) by others.
S_IROTH	Read by others.
S_IWOTH	Write by others.
S_IXOTH	Execute (search) by others.
S_ISVTX	On directories, restricted deletion flag.

Return Value

Errors

EACCES

Th	only portabl
fil	. If mod




The user ID of the file shall be initialized to the effective user
ID of the process. The group ID of the file shall be
initialized to either the effective group ID of the process or the
group ID of the parent directory. Implementations shall provide
a way to initialize the file's group ID to the group ID of the parent
directory. Implementations may, but need not, provide an
implementation-defined way to initialize the file's group ID to the
effective group ID of the calling process. The owner, group,
and other permission bits of mode shall be modified by the file
mode creation mask of the process. The mknod()
function shall clear each bit whose corresponding bit in the file
mode creation mask of the process is set.
If path names a symbolic link, mknod() shall fail and
set errno to [EEXIST].
Upon successful completion, mknod() shall mark for update the
st_atime, st_ctime, and st_mtime
fields of the file. Also, the st_ctime and st_mtime fields
of the directory that contains the new entry shall be
marked for update.
Only a process with appropriate privileges may invoke mknod()
for file types other than FIFO-special.
Upon successful completion, mknod() shall return 0. Otherwise,
it shall return -1, the new file shall not be created, and
errno shall be set to indicate the error.
The mknod() function shall fail if:
A component of the path prefix denies search permission, or write
permission is denied on the parent directory.

EEXIST

The named file exists.

EINVAL

An invalid argument exists.

EIO

An I/O error occurred while accessing the file system.

ELOOP

A loop exists in symbolic links encountered during resolution of the

path argument.

ENAMETOOLONG

The length of a pathname exceeds {PATH_MAX} or a pathname component

is longer than {NAME_MAX}.

ENOENT

A component of the path prefix specified by path does not name

an existing directory or path is an empty

string.

ENOSPC

The directory that would contain the new file cannot be extended or

the file system is out of file allocation resources.

ENOTDIR

A component of the path prefix is not a directory.

EPERM

The invoking process does not have appropriate privileges and the

file type is not FIFO-special.

EROFS

The directory in which the file is to be created is located on a read-only

file system.

ELOOP

The mknod() function may fail if:

More than {SYMLOOP_MAX} symbolic links were encountered during resolution

of the path argument.

ENAMETOOLONG

Pathname resolution of a symbolic link produced an intermediate result

whose length exceeds {PATH_MAX}.

Examples

Creating a FIFO Special File

#include <sys/types.h>#include <sys/stat.h>
dev_t dev;int   status;...status  = mknod("/home/cnd/mod_done", S_IFIFO | S_IWUSR
|    S_IRUSR | S_IRGRP | S_IROTH, dev);

Application Usage

Rationale

Future Directions

Copyright

The following sections are informative.

The following example shows how to create a FIFO special file named

/home/cnd/mod_done, with read/write permissions for

owner, and with read permissions for group and others.

The mkfifo() function is preferred over this function for making

FIFO special

files.

The POSIX.1-1990 standard required that the group ID of a newly created

file be set to the group ID of its parent directory or

to the effective group ID of the creating process. FIPS 151-2 required

that implementations provide a way to have the group ID be

set to the group ID of the containing directory, but did not prohibit

implementations also supporting a way to set the group ID to

the effective group ID of the creating process. Conforming applications

should not assume which group ID will be used. If it

matters, an application can use chown() to set the group ID

after the file is created,

or determine under what conditions the implementation will set the

desired group ID.

None.

chmod(), creat(), exec(), mkdir(), mkfifo()

open(), stat(), umask(), the Base

Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Electrical and Electronics Engineers, Inc and The Open Group. In the

event of any discrepancy between this version and the original IEEE and

The Open Group Standard, the original IEEE and The Open Group Standard

is the referee document. The original Standard can be obtained online at

http://www.opengroup.org/unix/online.html .