mkfifo(3)



MKFIFO(3)                  Linux Programmer's Manual                 MKFIFO(3)

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

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.

RETURN VALUE
       On  success mkfifo() and mkfifoat() return 0.  In the case of an error,
       -1 is returned (in which case, errno is set appropriately).

ERRORS
       EACCES One of the directories in pathname did not  allow  search  (exe-
              cute) 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 over-
              all 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 dan-
              gling 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 re-
              ferring to a file other than a directory.

VERSIONS
       mkfifoat() was added to glibc in version 2.4.  It is implemented  using
       mknodat(2), available on Linux since kernel 2.6.16.

ATTRIBUTES
       For  an  explanation  of  the  terms  used  in  this  section,  see at-
       tributes(7).

       +---------------------+---------------+---------+
       |Interface            | Attribute     | Value   |
       +---------------------+---------------+---------+
       |mkfifo(), mkfifoat() | Thread safety | MT-Safe |
       +---------------------+---------------+---------+
CONFORMING TO
       mkfifo(): POSIX.1-2001, POSIX.1-2008.

       mkfifoat(): POSIX.1-2008.

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

COLOPHON
       This  page  is  part of release 4.16 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
       https://www.kernel.org/doc/man-pages/.

GNU                               2017-09-15                         MKFIFO(3)

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