NAME

       mkfifo, mkfifoat - make a FIFO special file (a named pipe)

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #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:
               _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _ATFILE_SOURCE

DESCRIPTION

       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.

       See openat(2) for an explanation of the need for mkfifoat().

RETURN VALUE

       On success mkfifo() and mkfifoat() return 0.  On error, -1 is returned and errno is set to
       indicate the error.

ERRORS

       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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌───────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                      │ Attribute     │ Value   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │mkfifo(), mkfifoat()                                           │ Thread safety │ MT-Safe │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

VERSIONS

       It is implemented using mknodat(2).

STANDARDS

       POSIX.1-2008.

HISTORY

       mkfifo()
              POSIX.1-2001.

       mkfifoat()
              glibc 2.4.  POSIX.1-2008.

SEE ALSO

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