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

NAME         top

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

SYNOPSIS         top

       #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:

DESCRIPTION         top

       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.

       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         top

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

ERRORS         top

       EACCES One of the directories in pathname did not allow search
              (execute) 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.

              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.

              A component used as a directory in pathname is not, in fact, a

       EROFS  pathname refers to a read-only filesystem.

       The following additional errors can occur for mkfifoat():

       EBADF  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.

VERSIONS         top

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

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface            Attribute     Value   │
       │mkfifo(), mkfifoat() │ Thread safety │ MT-Safe │

CONFORMING TO         top

       mkfifo(): POSIX.1-2001, POSIX.1-2008.

       mkfifoat(): POSIX.1-2008.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 4.08 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

GNU                              2016-03-15                        MKFIFO(3)