MKFIFO(2) BSD System Calls Manual MKFIFO(2)
mkfifo, mkfifoat -- make a FIFO file
mkfifo(const char *path, mode_t mode);
mkfifoat(int fd, const char *path, mode_t mode);
mkfifo() creates a new FIFO file with name path. The access permissions
are specified by mode and restricted by the umask(2) of the calling
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
The mkfifoat() function is equivalent to mkfifo() except that where path
specifies a relative path, the newly created FIFO is created relative to
the directory associated with file descriptor fd instead of the current
If mkfifoat() is passed the special value AT_FDCWD (defined in <fcntl.h>)
in the fd parameter, the current working directory is used and the behav-
ior is identical to a call to mkfifo().
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
mkfifo() and mkfifoat() will fail and no FIFO will be created if:
[EOPNOTSUPP] The kernel has not been configured to support FIFOs.
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG] A component of a pathname exceeded NAME_MAX charac-
ters, or an entire pathname (including the terminating
NUL) exceeded PATH_MAX bytes.
[ENOENT] A component of the path prefix does not exist.
[EACCES] Search permission is denied for a component of the
[ELOOP] Too many symbolic links were encountered in translat-
ing the pathname.
[EROFS] The named file resides on a read-only file system.
[EEXIST] The named file exists.
[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 direc-
[ENOSPC] There are no free inodes on the file system on which
the FIFO is being created.
[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.
[EDQUOT] The user's quota of inodes on the file system on which
the FIFO is being created has been exhausted.
[EIO] An I/O error occurred while making the directory entry
or allocating the inode.
[EIO] An I/O error occurred while reading from or writing to
the file system.
[EFAULT] path points outside the process's allocated address
Additionally, mkfifoat() will fail if:
[EBADF] The path argument specifies a relative path and the fd
argument is neither AT_FDCWD nor a valid file descrip-
[ENOTDIR] The path argument specifies a relative path and the fd
argument is a valid file descriptor but it does not
reference a directory.
[EACCES] The path argument specifies a relative path but search
permission is denied for the directory which the fd
file descriptor references.
chmod(2), stat(2), umask(2)
The mkfifo and mkfifoat functions conform to IEEE Std 1003.1-2008
The mkfifoat function appeared in OpenBSD 5.0.
BSD April 28, 2017 BSD