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)):

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.

mkfifoat()

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).

mkfifo(1), close(2), open(2), read(2), stat(2), umask(2), write(2), fifo(7)