Re: appending to a file
mohi wrote:
hello everyone,
i have a program where i write a structure of 1020B to a file a number
of times and in the next run of the program i have to again write
those structures but by taking some count from the last structure
written on the file
so i write it like:
fstream file("xyz",ios::out|ios::in|ios::ate);
long pos=file.tellg();
pos-=sizeof(struct);
file.putg(pos,0);//position at pos
file.read(reinterpret_cast<char *>(&struct),sizeof(struct));
use struct.cout;///////
the problem is that after the read struct has a count which is of the
second last struct written
can some one help me why this gets two structs back in the file.
How do you know that it is what's happening? Can you print the
position? Can you examine the file at that position? Can you tell
exactly how far from the end the file gets positioned? What's the file
size? Do you know with certainty that the "last struct" actually does
get written to the file?
Direct access database can be tricky. To debug it you need to be able
to look at the file at the byte level, at the record level, and
understand how your data get written (or even if they get written).
V
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