在写文件时第一次写入时能实现 ,但删除后再写入的时候就实现不了,为什么?

[ruiyiiuo2007]

在写文件时第一次写入时能实现 ,但删除后再写入的时候就实现不了,为什么?
例:
FILE *fp = NULL;
fp = fopen("top.txt","b+");
if(fp)
{
fwrite(szSqlBuffer888,strlen(szSqlBuffer888),1,fp);
fclose(fp);

}

[awperpvip]

debug一下，fp始终为NULL
fopen失败，改一下打开方式，比如传参数为wb+试下OK.

[IfI]

用c++的话建议用标准c++的库.

这个例子中,你把文件删除了,却没有指定"如果文件不存在就创建它"的参数,所以获取文件指针失败.

按楼上说法,换成wb+试试.

[冷月清晖]

当然啦，关闭之后要再次打开呀

[冷月清晖]

多些判断 错误处理

if(NULL==(fp = fopen("top.txt","b+")))
/*文件没打开，报错*/
else
/*操作*/
if( 0==fclose( fp ) )
/*文件关闭*/
else
/*报错*/

[zywhuiss]

"fp = fopen("top.txt","b+");"
怎么MSDN里面对fopen的说明终没有"b+"这个参数?楼主认真看过MSDN吗?

[KenYuan2016]

Please choose the correct parameter in your code...

"r"
Opens for reading. If the file does not exist or cannot be found, the fopen call fails.
"w"
Opens an empty file for writing. If the given file exists, its contents are destroyed.
"a"
Opens for writing at the end of the file (appending) without removing the EOF marker before writing new data to the file; creates the file first if it doesn't exist.
"r+"
Opens for both reading and writing. (The file must exist.)
"w+"
Opens an empty file for both reading and writing. If the given file exists, its contents are destroyed.
"a+"
Opens for reading and appending; the appending operation includes the removal of the EOF marker before new data is written to the file and the EOF marker is restored after writing is complete; creates the file first if it doesn't exist.

[xiao_ke]

是啊 你那個b+ 。。。。。。。

[ruiyiiuo2007]

多谢谢呀.