c语言fopen_s的用法,fopen和fopen_s用法的比较-优快云博客

本文通过示例代码详细介绍了fopen与fopen_s两种文件打开方式的区别。fopen_s相较于fopen增加了安全性检查，能更好地防止缓冲区溢出等问题。文中还展示了如何使用fopen_s进行文件读写操作及错误处理。

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在定义FILE * fp 之后，fopen的用法是: fp = fopen(filename,"w")。而对于fopen_s来说，还得定义另外一个变量errno_t err，然后err = fopen_s(&fp,filename,"w")。返回值的话，对于fopen来说，打开文件成功的话返回文件指针(赋值给fp)，打开失败则返回NULL值；对于fopen_s来说，打开文件成功返回0，失败返回非0。

在vs编程中，经常会有这样的警告：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.是因为 fopen_s比fopen多了溢出检测，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 ); }