MKFIFO(3) manual page
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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:
- _XOPEN_SOURCE >= 700 || _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.
The mkfifo() and mkfifoat() functions are thread-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)
This
page is part of release 3.78 of the Linux man-pages project. A description
of the project, information about reporting bugs, and the latest version
of this page, can be found at http://www.kernel.org/doc/man-pages/.
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