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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 (consult 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 implementa-
       tion-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 spe-
       cial files. The mknod()  function  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 directory or to the effective
       group  ID of the creating process. FIPS 151-2 required that implementa-
       tions provide a way to have the group ID be set to the group ID of  the
       containing  directory,  but  did not prohibit implementations also sup-
       porting a way to set the group ID to the effective group ID of the cre-
       ating 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, Copyright (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.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                           MKFIFO(3P)