fopen - C - fopen_s cannot write to a file made by CreateFile -

i have main.c function , subfunction called within it. in subfunction have used createfile make file. use closehandle close handle file. when use fopen_s after (within subfunction) works both read , write modes. if use fopen_s in main function afterwards, can open read access, or else error code 13 - permission denied. parameters of createfile function follows:

happend = createfile(centraldatafilepath, // open central data file                 file_append_data,         // open writing                 file_share_read|file_share_write,     // allow multiple readers                 null,                     // no security                 open_always,              // open or create                 file_attribute_normal,    // normal file                 null);                    // no attr. template 

and use fopen_s follows:

file *f2; errno_t errorcode3 = 0; errorcode3 = fopen_s(&f2, centraldatafilepath, "a+"); fclose(f2); 

i don't know if createfile has this, seems permission of file changes after exit subfunction? need able write file, know why getting permission denied error, , how fix it?

as described here:

files opened fopen_s , _wfopen_s not sharable.

function failed because can't lock file writing. need use _fsopen instead. try this:

f2 = _fsopen(centraldatafilepath, "a+", _sh_denyno);