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.\"	$NetBSD: mkdir.2,v 1.8 1995/02/27 12:34:22 cgd Exp $
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.\"     @(#)mkdir.2	8.2 (Berkeley) 12/11/93
.\"
.Dd December 11, 1993
.Dt MKDIR 2
.Os BSD 4.2
.Sh NAME
.Nm mkdir ,
.Nm mkdirat
.Nd make a directory file
.Sh SYNOPSIS
.Fd #include <sys/stat.h>
.Ft int
.Fo mkdir
.Fa "const char *path"
.Fa "mode_t mode"
.Fc
.Ft int
.Fn mkdirat "int fd" "const char *path" "mode_t mode"
.Sh DESCRIPTION
The directory
.Fa path
is created with the access permissions specified by
.Fa mode
and restricted by the
.Xr umask 2
of the calling process. See
.Xr chmod 2
for the possible permission bit masks for
.Fa mode . 
.Pp
The directory's owner ID is set to the process's effective user ID.
The directory's group ID is set to that of the parent directory in
which it is created.
.Pp
Note: the behavior of
.Fn mkdir
is undefined when mode bits other than the low 9 bits are used. Use
.Xr chmod 2
after
.Fn mkdir
to explicitly set the other bits (See example below).
.Pp
The
.Fn mkdirat
system call is equivalent to
.Fn mkdir
except in the case where
.Fa path
specifies a relative path.
In this case the newly created directory is created relative to the
directory associated with the file descriptor
.Fa fd
instead of the current working directory.
If
.Fn mkdirat
is passed the special value
.Dv AT_FDCWD
in the
.Fa fd
parameter, the current working directory is used and the behavior is
identical to a call to
.Fn mkdir .
.Sh RETURN VALUES
A 0 return value indicates success.  A -1 return value
indicates an error, and an error code is stored in
.Va errno .
.Sh ERRORS
.Fn mkdir
will fail and no directory will be created if:
.Bl -tag -width Er
.\" ==========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ==========
.It Bq Er EACCES
Write permission is denied for the parent directory.
.\" ==========
.It Bq Er EDQUOT
The new directory cannot be created because the user's
quota of disk blocks on the file system that will
contain the directory has been exhausted.
.\" ==========
.It Bq Er EDQUOT
The user's quota of inodes on the file system on
which the directory is being created has been exhausted.
.\" ==========
.It Bq Er EEXIST
The named file exists.
.\" ==========
.It Bq Er EFAULT
.Fa Path
points outside the process's allocated address space.
.\" ==========
.It Bq Er EIO
An I/O error occurred while making the directory entry
or allocating the inode.
.\" ==========
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.\" ==========
.It Bq Er EISDIR
The named file is the root directory.
.\" ==========
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
.\" ==========
.It Bq Er EMLINK
The parent directory already has {LINK_MAX} links.
.\" ==========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 
.Dv {NAME_MAX}
characters, or an entire path name exceeded 
.Dv {PATH_MAX}
characters.
.\" ==========
.It Bq Er ENOENT
A component of the path prefix does not exist
or path is an empty string.
.It Bq Er ENOSPC
The new directory cannot be created because there is no space left
on the file system that would contain it.
.\" ==========
.It Bq Er ENOSPC
There are no free inodes on the file system on which the
directory is being created.
.\" ==========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.\" ==========
.It Bq Er EROFS
The parent directory resides on a read-only file system.
.El
.Pp
In addition to the errors returned by the
.Fn mkdir ,
the
.Fn mkdirat
function may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.It Bq Eq EILSEQ
The filename does not match the encoding rules.
.El
.Sh EXAMPLE
.Bd -literal -offset indent

int main (int argc, const char * argv[]) 
{
	/* The behavior of mkdir is undefined for anything other than the "permission" bits */
	if (mkdir("/tmp/blah", 0777))
		perror("/tmp/blah");	

	/* So we need to set the sticky/executable bits explicitly with chmod after calling mkdir */
	if (chmod("/tmp/blah", 07777))
		perror("/tmp/blah");	
}

.Ed 
.Sh LEGACY SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Pp
The include file
.In sys/types.h
is necessary.
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr stat 2 ,
.Xr umask 2 ,
.Xr compat 5
.Sh STANDARDS
The 
.Fn mkdir
function conforms to 
.St -p1003.1-88 .
The
.Fn mkdirat
system call is expected to conform to POSIX.1-2008 .
.Sh HISTORY
The
.Fn mkdirat
system call appeared in OS X 10.10