fo

Algorithms for Image Processing and Computer Vision Source Code

@c ----------------------------------------------------------------------
@node fopen, stdio
@heading @code{fopen}
@subheading Syntax

@example
#include <stdio.h>
FILE *fopen(const char *filename, const char *mode);
@end example

@subheading Description

This function opens a stream corresponding to the named @var{filename}
with the given @var{mode}.  The mode can be one of the following:

@table @code

@item r

Open an existing file for reading.

@item w

Create a new file (or truncate an existing file) and open it for
writing. 

@item a

Open an existing file (or create a new one) for writing.  The file
pointer is positioned to the end of the file before every write. 

@end table

Followed by any of these characters:

@table @code

@item b

Force the file to be open in binary mode instead of the default mode.

@item t

Force the file to be open in text mode instead of the default mode.

@item +

Open the file as with @code{O_RDWR} so that both reads and writes
can be done to the same file.

@end table

If the file is open for both reading and writing, you must call
@code{fflush}, @code{fseek}, or @code{rewind} before switching from read
to write or from write to read. 

The open file is set to line buffered if the underlying object is a
device (stdin, stdout, etc), or is fully buffered if the underlying
object is a disk file (data.c, etc).

If @code{b} or @code{t} is not specified in @var{mode}, the file type is
chosen by the value of @code{fmode} (@pxref{_fmode}). 

@subheading Return Value

A pointer to the @code{FILE} object, or @code{NULL} if there was an
error. 

@subheading Example

@example
FILE *f = fopen("foo", "rb+"); /* open existing file for read/write, binary mode */
@end example

@c ----------------------------------------------------------------------
@node fork, unix
@heading @code{fork}

@subheading Description

This function always returns -1, as MS-DOS does not support multiple
processes.  It exists only to assist in porting Unix programs.