mkfifo, mkfifoat - make a FIFO special file (a named pipe)
int mkfifo(const char *pathname, mode_t mode);
#include <fcntl.h> /* Definition of AT_* constants */
int mkfifoat(int dirfd, const char *pathname, mode_t mode);
Feature Test Macro Requirements for glibc (see feature_test_macros
- Since glibc 2.10:
- _POSIX_C_SOURCE >= 200809L
- Before glibc 2.10:
() makes a FIFO special file with name pathname
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
(7) for nonblocking handling of FIFO special files.
() function operates in exactly the same way as
(), 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).
is relative and dirfd
is the special value
, then pathname
is interpreted relative to the current
working directory of the calling process (like mkfifo
is absolute, then dirfd
On success mkfifo
() and mkfifoat
() return 0. In the case of an
error, -1 is returned (in which case, errno
is set appropriately).
- One of the directories in pathname did not allow search (execute)
- The user's quota of disk blocks or inodes on the filesystem has been
- pathname already exists. This includes the case where
pathname is a symbolic link, dangling or not.
- 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.
- A directory component in pathname does not exist or is a dangling
- The directory or filesystem has no room for the new file.
- A component used as a directory in pathname is not, in fact, a
- pathname refers to a read-only filesystem.
The following additional errors can occur for mkfifoat
- dirfd is not a valid file descriptor.
- pathname is a relative path and dirfd is a file descriptor
referring to a file other than a directory.
() was added to glibc in version 2.4. It is implemented using
(2), available on Linux since kernel 2.6.16.
For an explanation of the terms used in this section, see attributes
|mkfifo (), mkfifoat ()
(): POSIX.1-2001, POSIX.1-2008.