Can a failed fopen impact the filesystem?

Question

If fopen( path, "w" ) succeeds, then the file will be truncated. If the fopen fails, are there an guarantees that the file is not modified?

Answer 1

No there are no guarantees about the state of a file if fopen(path, "w") fails. The failure could be coming from any operation from opening the file, committing the truncation to disk, etc ... The only guarantee a failure provides is that you don't have access to the file.