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

PROLOG

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

NAME

       fdopen - associate a stream with a file descriptor

SYNOPSIS

       #include <stdio.h>

       FILE *fdopen(int fildes, const char *mode);

DESCRIPTION

       The fdopen() function shall associate a stream with a file descriptor.

       The mode argument is a character string having one of the following values:

       r or rb
	      Open a file for reading.

       w or wb
	      Open a file for writing.

       a or ab
	      Open a file for writing at end-of-file.

       r+ or rb+ or r+b
	      Open a file for update (reading and writing).

       w+ or wb+ or w+b
	      Open a file for update (reading and writing).

       a+ or ab+ or a+b
	      Open a file for update (reading and writing) at end-of-file.

       The meaning of these flags is exactly as specified in fopen(), except that modes beginning with w shall not cause truncation of the file.

       Additional values for the mode argument may be supported by an implementation.

       The application shall ensure that the mode of the stream as expressed by the mode argument is allowed by the file access mode of  the  open
       file description to which fildes refers. The file position indicator associated with the new stream is set to the position indicated by the
       file offset associated with the file descriptor.

       The error and end-of-file indicators for the stream shall be cleared.  The fdopen() function may cause the st_atime field of the underlying
       file to be marked for update.

       If fildes refers to a shared memory object, the result of the fdopen() function is unspecified.

       If fildes refers to a typed memory object, the result of the fdopen() function is unspecified.

       The fdopen() function shall preserve the offset maximum previously set for the open file description corresponding to fildes.

RETURN VALUE

       Upon successful completion, fdopen() shall return a pointer to a stream; otherwise, a null pointer shall be returned and errno set to indi-
       cate the error.

ERRORS

       The fdopen() function may fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       EINVAL The mode argument is not a valid mode.

       EMFILE {FOPEN_MAX} streams are currently open in the calling process.

       EMFILE {STREAM_MAX} streams are currently open in the calling process.

       ENOMEM Insufficient space to allocate a buffer.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       File descriptors are obtained from calls like open(), dup(), creat(), or pipe(), which open files but do not return streams.

RATIONALE

       The file descriptor may have been obtained from open(), creat(), pipe(), dup(), or fcntl(); inherited through fork() or	exec;  or  perhaps
       obtained by implementation-defined means, such as the 4.3 BSD socket() call.

       The  meanings  of the mode arguments of fdopen() and fopen() differ.  With fdopen(), open for write (w or w+) does not truncate, and append
       (a or a+) cannot create for writing. The mode argument formats that include a b are allowed for consistency with the ISO C  standard  func-
       tion  fopen(). The b has no effect on the resulting stream. Although not explicitly required by this volume of IEEE Std 1003.1-2001, a good
       implementation of append (a) mode would cause the O_APPEND flag to be set.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Interaction of File Descriptors and Standard I/O Streams, fclose(), fopen(), open(), the Base Definitions volume  of  IEEE Std 1003.1-2001,
       <stdio.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- 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								FDOPEN(3P)