mknod(2)
NAME
mknod - make a directory, or a special or ordinary file
SYNOPSIS
#include <sys/stat.h>
int mknod(const char *path, mode_t mode, dev_t dev);
DESCRIPTION
The mknod() function creates a new file named by the path
name pointed to by path. The file type and permissions of
the new file are initialized from mode.
The file type is specified in mode by the S_IFMT bits, which
must be set to one of the following values:
S_IFIFO
fifo special
S_IFCHR
character special
S_IFDIR
directory
S_IFBLK
block special
S_IFREG
ordinary file
The file access permissions are specified in mode by the
0007777 bits, and may be constructed by a bitwise OR opera-
tion of the following values:
S_ISUID 04000 Set user ID on execution.
S_ISGID 020#0 Set group ID on execution if # is
7, 5, 3, or 1. Enable mandatory
file/record locking if # is 6, 4,
2, or 0
S_ISVTX 01000 On directories, restricted deletion
flag; on regular files on a UFS
file system, do not cache flag.
S_IRWXU 00700 Read, write, execute by owner.
S_IRUSR 00400 Read by owner.
S_IWUSR 00200 Write by owner.
S_IXUSR 00100 Execute (search if a directory) by
owner.
S_IRWXG 00070 Read, write, execute by group.
S_IRGRP 00040 Read by group.
S_IWGRP 00020 Write by group.
S_IXGRP 00010 Execute by group.
S_IRWXO 00007 Read, write, execute (search) by
others.
S_IROTH 00004 Read by others.
S_IWOTH 00002 Write by others
S_IXOTH 00001 Execute by others.
The owner ID of the file is set to the effective user ID of
the process. The group ID of the file is set to the effec-
tive group ID of the process. However, if the S_ISGID bit
is set in the parent directory, then the group ID of the
file is inherited from the parent. If the group ID of the
new file does not match the effective group ID or one of the
supplementary group IDs, the S_ISGID bit is cleared.
The access permission bits of mode are modified by the
process's file mode creation mask: all bits set in the
process's file mode creation mask are cleared (see
umask(2)). If mode indicates a block or character special
file, dev is a configuration-dependent specification of a
character or block I/O device. If mode does not indicate a
block special or character special device, dev is ignored.
See makedev(3C).
If path is a symbolic link, it is not followed.
RETURN VALUES
Upon successful completion, mknod() returns 0. Otherwise, it
returns -1, the new file is not created, and errno is set to
indicate the error.
ERRORS
The mknod() function will fail if:
EACCES
A component of the path prefix denies search permis-
sion, or write permission is denied on the parent
directory.
EDQUOT
The directory where the new file entry is being placed
cannot be extended because the user's quota of disk
blocks on that file system has been exhausted, or the
user's quota of inodes on the file system where the
file is being created has been exhausted.
EEXIST
The named file exists.
EFAULT
The path argument points to an illegal address.
EINTR A signal was caught during the execution of the
mknod() function.
EINVAL
An invalid argument exists.
EIO An I/O error occurred while accessing the file system.
ELOOP Too many symbolic links were encountered in translat-
ing path.
ENAMETOOLONG
The length of the path argument exceeds PATH_MAX, or
the length of a path component exceeds NAME_MAX while
_POSIX_NO_TRUNC is in effect.
ENOENT
A component of the path prefix specified by path does
not name an existing directory or path is an empty
string.
ENOLINK
The path argument points to a remote machine and the
link to that machine is no longer active.
ENOSPC
The directory that would contain the new file cannot
be extended or the file system is out of file alloca-
tion resources.
ENOTDIR
A component of the path prefix is not a directory.
EPERM The effective user of the calling process is not
super-user.
EROFS The directory in which the file is to be created is
located on a read-only file system.
The mknod() function may fail if:
ENAMETOOLONG
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds PATH_MAX.
USAGE
Normally, applications should use the mkdir(2) routine to
make a directory, since the function mknod() may not estab-
lish directory entries for the directory itself (.) and the
parent directory (..), and appropriate permissions are not
required. Similarly, mkfifo(3C) should be used in place of
mknod() in order to create FIFOs.
The mknod() function may be invoked only by a privileged
user for file types other than FIFO special.
When a UFS file system is mounted with logging enabled, file
system transactions that free blocks from files might not
actually add those freed blocks to the file system's free
list until some unspecified time in the future. This
behavior improves file system performance but does not con-
form to the POSIX, Single UNIX Specification, SPARC Confor-
mance Definition, System V Application Binary Interface,
System V Interface Definition, and X/Open Portability Guide
Standards, which require that freed space be available
immediately. To enable standards conformance regarding file
deletions or to address the problem of not being able to
grow files on a relatively full UFS file system even after
files have been deleted, disable UFS logging (see
mount_ufs(1M).
SEE ALSO
mount_ufs(1M), chmod(2), creat(2), exec(2), mkdir(2),
open(2), stat(2), umask(2), makedev(3C), mkfifo(3C),
stat(3HEAD)
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