今天使用公司代码的日志模块记录程序运行的相关信息,发现日志总是只有两条记录,即程序启动和结束,别的都没有。跟踪了很久,终于发现是日志输出模块被我修改了一个地方:把fopen改成了fopen_s,毕竟报了warning。但是这也是问题的根源!
下面的说明来自于msdn:
Files opened by fopen_s and _wfopen_s are not sharable. If you require that a file be sharable, use _fsopen, _wfsopen with the appropriate sharing mode constant (for example, _SH_DENYNO for read/write sharing).
fopen_s打开的文件不是共享读写的!但是日志模块需要反复在同一个文件中读写,而且每次都调用了fopen_s,第二次调用的时候当然会出错了,错误代码是13,也就是EACCES (Permission denied)
这里应该使用_fsopen:
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#include <stdio.h> #include <stdlib.h> #include <share.h> int main( void ) { FILE *stream; // Open output file for writing. Using _fsopen allows us to // ensure that no one else writes to the file while we are // writing to it. // if ( (stream = _fsopen( "outfile" , "wt" , _SH_DENYWR )) != NULL ) { fprintf ( stream, "No one else in the network can write " "to this file until we are done.
" ); fclose ( stream ); } // Now others can write to the file while we read it. system ( "type outfile" ); } |
(以上代码来自于msdn,版权归原作者所有)