參考：

在定義FILE * fp 之后，fopen的用法是:?fp?= fopen(filename,"w")。而對于fopen_s來說，還得定義另外一個變量errno_t err，然后err = fopen_s(&fp,filename,"w")。返回值的話，對于fopen來說，打開文件成功的話返回文件指針(賦值給fp)，打開失敗則返回NULL值；對于fopen_s來說，打開文件成功返回0，失敗返回非0。

在vs編程中，經常會有這樣的警告：warning C4996: 'fopen': This function or variable may be unsafe. Consider using fopen_s instead. To disable deprecation, use_CRT_SECURE_NO_WARNINGS. See online help for details.是因為? fopen_s比fopen多了溢出檢測，更安全一些。

#include

FILE *stream, *stream2;

int main( void ) { ?? int numclosed; ?? errno_t err;

// Open for read (will fail if file "crt_fopen_s.c" does not exist) ?? if( (err? = fopen_s( &stream, "crt_fopen_s.c", "r" )) !=0 ) ????? printf( "The file 'crt_fopen_s.c' was not opened\n" ); ?? else ????? printf( "The file 'crt_fopen_s.c' was opened\n" );

// Open for write? ?? if( (err = fopen_s( &stream2, "data2", "w+" )) != 0 ) ????? printf( "The file 'data2' was not opened\n" ); ?? else ????? printf( "The file 'data2' was opened\n" );

// Close stream if it is not NULL? ?? if( stream) ?? { ????? if ( fclose( stream ) ) ????? { ???????? printf( "The file 'crt_fopen_s.c' was not closed\n" ); ????? } ?? }

// All other files are closed: ?? numclosed = _fcloseall( ); ?? printf( "Number of files closed by _fcloseall: %u\n", numclosed ); }