fscanf %*s_fscanf double_fscanf函数

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")。返回的话，对于fopen来说，打开文件成功的话返回文件指针（赋给fp），打开失败则返回NULL；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：warning996: 'fopen': This function or variable may be unsafe. Considerusing fopen_s instead. To disable deprecation,use_CRT_SECURE_NO_WARNINGS. See online help fordetails.是因为fopen_s比fopen多了溢出检测，更安全一些。（在以后的文章里还有get与get_s的比较,strcpystrcpy_s的比较，他们的共同点都是用来一些不可预料的行为，以后将进行详尽解释）

#include

FILE *stream,*stream2;

int main( void)

{

int numclosed;

errno_t err;

// Open for read (will fail if file "crt_fopen_s.c" does notexist)

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 filesclosed by _fcloseall: %u\n", numclosed );

}

fscanf和fscanf_s用法的比较

fscanf和fscanf_s

fscanf用法：fscanf(fp,"%d",&var)

fscanf_s用法：fscanf(fp,"%d",&var,sizeof(int))

本文来自电脑杂谈，转载请注明本文网址：
http://www.pc-fly.com/a/jisuanjixue/article-21618-1.html