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)):
- Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
- Before glibc 2.10:
mkfifo() makes a FIFO special file with name
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.
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
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
pathname is absolute, then
dirfd is ignored.
One of the directories in
pathname did not allow search
The user's quota of disk blocks or inodes on the filesystem has been exhausted.
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 symbolic link.
The directory or filesystem has no room for the new file.
A component used as a directory in
pathname is not, in fact,
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.
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