.\"	$OpenBSD: mkfifo.2,v 1.9 2011/07/18 23:04:40 matthew Exp $
.\"	$NetBSD: mkfifo.2,v 1.8 1995/02/27 12:34:27 cgd Exp $
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.\"	@(#)mkfifo.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: July 18 2011 $
.Dt MKFIFO 2
.Os
.Sh NAME
.Nm mkfifo ,
.Nm mkfifoat
.Nd make a FIFO file
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Fd #include <fcntl.h>
.Ft int
.Fn mkfifo "const char *path" "mode_t mode"
.Ft int
.Fn mkfifoat "int fd" "const char *path" "mode_t mode"
.Sh DESCRIPTION
.Fn mkfifo
creates a new FIFO file with name
.Fa path .
The access permissions are
specified by
.Fa mode
and restricted by the
.Xr umask 2
of the calling process.
.Pp
The FIFO's owner ID is set to the process's effective user ID.
The FIFO's group ID is set to that of the parent directory in
which it is created.
.Pp
The
.Fn mkfifoat
function is equivalent to
.Fn mkfifo
except that where
.Fa path
specifies a relative path,
the newly created FIFO is created relative to
the directory associated with file descriptor
.Fa fd
instead of the current working directory.
.Pp
If
.Fn mkfifoat
is passed the special value
.Dv AT_FDCWD
(defined in
.In fcntl.h )
in the
.Fa fd
parameter, the current working directory is used
and the behavior is identical to a call to
.Fn mkfifo .
.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 mkfifo
and
.Fn mkfifoat
will fail and no FIFO will be created if:
.Bl -tag -width Er
.It Bq Er EOPNOTSUPP
The kernel has not been configured to support FIFOs.
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.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.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EROFS
The named file resides on a read-only file system.
.It Bq Er EEXIST
The named file exists.
.It Bq Er ENOSPC
The directory in which the entry for the new FIFO is being placed
cannot be extended because there is no space left on the file
system containing the directory.
.It Bq Er ENOSPC
There are no free inodes on the file system on which the
FIFO is being created.
.It Bq Er EDQUOT
The directory in which the entry for the new FIFO
is being placed cannot be extended because the
user's quota of disk blocks on the file system
containing the directory has been exhausted.
.It Bq Er EDQUOT
The user's quota of inodes on the file system on
which the FIFO is being created has been exhausted.
.It Bq Er EIO
An
.Tn I/O
error occurred while making the directory entry or allocating the inode.
.It Bq Er EIO
An
.Tn I/O
error occurred while reading from or writing to the file system.
.It Bq Er EFAULT
.Fa path
points outside the process's allocated address space.
.El
.Pp
Additionally,
.Fn mkfifoat
will 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 reading.
.El
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr stat 2 ,
.Xr umask 2
.Sh STANDARDS
The
.Nm mkfifo
and
.Nm mkfifoat
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Nm mkfifoat
function appeared in
.Ox 5.0 .