fclose requires as its argument a FILE pointer obtained either by fopen, one of the standard streams stdin, stdout, or stderr, or in some other implementation-defined way. A null pointer is not one of these, so the behavior is undefined, just like fclose((FILE *)0xdeadbeef) would be. NULL is not special in C; aside from the … Read more
You typically have to do this in a single syscall, or else you will get a race condition. This will open for reading and writing, creating the file if necessary. FILE *fp = fopen(“scores.dat”, “ab+”); If you want to read it and then write a new version from scratch, then do it as two steps. … Read more
As long as your program is running, if you keep opening files without closing them, the most likely result is that you will run out of file descriptors/handles available for your process, and attempting to open more files will fail eventually. On Windows, this can also prevent other processes from opening or deleting the files … Read more