mkfifo, mkfifoat - make a FIFO special file (a named pipe)
Standard C library (
libc,
-lc)
#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);
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.
See
openat(2) for an explanation of the need for
mkfifoat().
On success
mkfifo() and
mkfifoat() return 0. On error, -1 is
returned and
errno is set to indicate the error.
- EACCES
- One of the directories in pathname did not allow
search (execute) permission.
- EBADF
- (mkfifoat()) pathname is relative but
dirfd is neither AT_FDCWD nor a valid file descriptor.
- 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.
- ENOTDIR
- (mkfifoat()) pathname is a relative pathname
and dirfd is a file descriptor referring to a file other than a
directory.
- EROFS
-
pathname refers to a read-only filesystem.
mkfifoat() was added in glibc 2.4. It is implemented using
mknodat(2), available since Linux 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)