MKFIFO(3P)                                          POSIX Programmer's Manual                                         MKFIFO(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       mkfifo - make a FIFO special file

SYNOPSIS
       #include <sys/stat.h>

       int mkfifo(const char *path, mode_t mode);


DESCRIPTION
       The  mkfifo() function shall create a new FIFO special file named by the pathname pointed to by path. The file permission
       bits of the new FIFO shall be initialized from mode.  The file permission bits of the mode argument shall be modified  by
       the process' file creation mask.

       When bits in mode other than the file permission bits are set, the effect is implementation-defined.

       If path names a symbolic link, mkfifo() shall fail and set errno to [EEXIST].

       The  FIFO's  user ID shall be set to the process' effective user ID.  The FIFO's group ID shall be set to the group ID of
       the parent directory or to the effective group ID of the process. Implementations shall provide a way to  initialize  the
       FIFO's  group  ID  to the group ID of the parent directory. Implementations may, but need not, provide an implementation-
       defined way to initialize the FIFO's group ID to the effective group ID of the calling process.

       Upon successful completion, mkfifo() shall mark for update the st_atime, st_ctime, and st_mtime fields of the file. Also,
       the st_ctime and st_mtime fields of the directory that contains the new entry shall be marked for update.

RETURN VALUE
       Upon  successful  completion,  0  shall be returned. Otherwise, -1 shall be returned, no FIFO shall be created, and errno
       shall be set to indicate the error.

ERRORS
       The mkfifo() function shall fail if:

       EACCES A component of the path prefix denies search permission, or write permission is denied on the parent directory  of
              the FIFO to be created.

       EEXIST The named file already exists.

       ELOOP  A loop exists in symbolic links encountered during resolution of the path argument.

       ENAMETOOLONG
              The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

       ENOENT A component of the path prefix specified by path does not name an existing directory or path is an empty string.

       ENOSPC The  directory  that  would  contain  the new file cannot be extended or the file system is out of file-allocation
              resources.

       ENOTDIR
              A component of the path prefix is not a directory.

       EROFS  The named file resides on a read-only file system.


       The mkfifo() function may fail if:

       ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.

       ENAMETOOLONG
              As a result of encountering a symbolic link in resolution of the path argument,  the  length  of  the  substituted
              pathname string exceeded {PATH_MAX}.


       The following sections are informative.

EXAMPLES
   Creating a FIFO File
       The  following  example  shows how to create a FIFO file named /home/cnd/mod_done, with read/write permissions for owner,
       and with read permissions for group and others.


              #include <sys/types.h>
              #include <sys/stat.h>


              int status;
              ...
              status = mkfifo("/home/cnd/mod_done", S_IWUSR | S_IRUSR |
                  S_IRGRP | S_IROTH);

APPLICATION USAGE
       None.

RATIONALE
       The syntax of this function is intended to maintain compatibility with historical implementations of mknod(). The  latter
       function  was included in the 1984 /usr/group standard but only for use in creating FIFO special files. The mknod() func-
       tion was originally excluded from the POSIX.1-1988  standard  as  implementation-defined  and  replaced  by  mkdir()  and
       mkfifo(). The mknod() function is now included for alignment with the Single UNIX Specification.

       The  POSIX.1-1990 standard required that the group ID of a newly created FIFO be set to the group ID of its parent direc-
       tory or to the effective group ID of the creating process. FIPS 151-2 required that implementations provide a way to have
       the  group  ID be set to the group ID of the containing directory, but did not prohibit implementations also supporting a
       way to set the group ID to the effective group ID of the creating process.  Conforming  applications  should  not  assume
       which group ID will be used. If it matters, an application can use chown() to set the group ID after the FIFO is created,
       or determine under what conditions the implementation will set the desired group ID.

FUTURE DIRECTIONS
       None.

SEE ALSO
       umask(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>, <sys/types.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    MKFIFO(3P)