Syntax:

    #include <cstdio>
    FILE *fopen( const char *fname, const char *mode );

The fopen() function opens a file indicated by fname and returns a stream associated with that file. mode is used to determine how the file will be treated (i.e. for input, output, etc).

If there is an error, fopen() returns NULL.

Mode	Meaning	Already Exists	Does Not Exist
“r”	Open a file for reading	read from start	error
“w”	Create a file for writing	destroy contents	create new
“a”	Append to a file	write to end	create new
“r+“	Open a file for read/write	read from start	error
“w+“	Create a file for read/write	destroy contents	create new
“a+“	Open a file for read/write	write to end	create new

You can also optionally specify the “b” flag to open a file in binary mode on Windows systems. This flag is ignored on POSIX systems (including Linux), so it's safe to always specify this flag when operating on binary files.

An example:

     int ch;
     FILE *input = fopen( "stuff", "r" );
     ch = getc( input );

Related Topics: fclose, fflush, fgetc, fputc, fread, freopen, fseek, fwrite, getc, getchar, setbuf