mkfifo, mkfifoat - make a FIFO special file (a named pipe)
#include <sys/types.h>
#include <sys/stat.h>
int mkfifo(const char *pathname, mode_t mode);
#include <fcntl.h> /* Definition of AT_* constants */
#include <sys/stat.h>
int mkfifoat(int dirfd, const char *pathname, mode_t mode);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
mkfifoat():
- Since glibc 2.10:
- _POSIX_C_SOURCE >= 200809L
- Before glibc 2.10:
- _ATFILE_SOURCE
mkfifo() makes a FIFO special file with name
pathname.
mode
specifies the FIFO's permissions. It is modified by the process's
umask
in the usual way: the permissions of the created file are
(mode & ~umask).
A FIFO special file is similar to a pipe, except that it is created in a
different way. Instead of being an anonymous communications channel, a FIFO
special file is entered into the filesystem by calling
mkfifo().
Once you have created a FIFO special file in this way, any process can open it
for reading or writing, in the same way as an ordinary file. However, it has
to be open at both ends simultaneously before you can proceed to do any input
or output operations on it. Opening a FIFO for reading normally blocks until
some other process opens the same FIFO for writing, and vice versa. See
fifo(7) for nonblocking handling of FIFO special files.
The
mkfifoat() function operates in exactly the same way as
mkfifo(), except for the differences described here.
If the pathname given in
pathname is relative, then it is interpreted
relative to the directory referred to by the file descriptor
dirfd
(rather than relative to the current working directory of the calling process,
as is done by
mkfifo() for a relative pathname).
If
pathname is relative and
dirfd is the special value
AT_FDCWD, then
pathname is interpreted relative to the current
working directory of the calling process (like
mkfifo()).
If
pathname is absolute, then
dirfd is ignored.
On success
mkfifo() and
mkfifoat() return 0. In the case of an
error, -1 is returned (in which case,
errno is set appropriately).
- EACCES
- One of the directories in pathname did not allow search (execute)
permission.
- EDQUOT
- The user's quota of disk blocks or inodes on the filesystem has been
exhausted.
- EEXIST
- pathname already exists. This includes the case where
pathname is a symbolic link, dangling or not.
- ENAMETOOLONG
- Either the total length of pathname is greater than
PATH_MAX, or an individual filename component has a length greater
than NAME_MAX. In the GNU system, there is no imposed limit on
overall filename length, but some filesystems may place limits on the
length of a component.
- ENOENT
- A directory component in pathname does not exist or is a dangling
symbolic link.
- ENOSPC
- The directory or filesystem has no room for the new file.
- ENOTDIR
- A component used as a directory in pathname is not, in fact, a
directory.
- EROFS
- pathname refers to a read-only filesystem.
The following additional errors can occur for
mkfifoat():
- EBADF
- dirfd is not a valid file descriptor.
- ENOTDIR
- pathname is a relative path and dirfd is a file descriptor
referring to a file other than a directory.
mkfifoat() was added to glibc in version 2.4. It is implemented using
mknodat(2), available on Linux since kernel 2.6.16.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
mkfifo (), mkfifoat () |
Thread safety |
MT-Safe |
mkfifo(): POSIX.1-2001, POSIX.1-2008.
mkfifoat(): POSIX.1-2008.
mkfifo(1),
close(2),
open(2),
read(2),
stat(2),
umask(2),
write(2),
fifo(7)