| NSFileHandle is a kind of wrapper of UNIX file descriptor: you can extract the file descriptor using | [myFileHandle fileDescriptor] method. Then the standard fdopen routine will give you a pointer on a FILE structure.
That's the easy part. But now: which one do you need to close first: the FILE* by using fclose or the NSFileHandle using [myFileHandle closeFile] method ?
The problem is as following: if you fclose(myFILE) first, then when releasing or closing the myFileHandle instance variable you will get an exception because the descriptor is already closed as a side effect. So lets close or release the myFileHandle before ? In that case, fclose will also return an error because of the now invalid file descriptor it is wrapping. Note that not calling fclose creates a memory leaks because the FILE structure internally allocated by fdopen is not released.
One could think that closing the descriptor with [myFileHandle closeFile] and then free(myFile) is the solution. But we don't know if every implementations of fdopen allocate their FILE structures with malloc. Advice: avoid mixing NSFileHandle and FILE*…
The solution is simply to use [[myFileHandle writeData:[[NSString stringWithFormat:…] dataUsingEncoding:myEncodingForThisJob]].
stringWithFormat easily replace fprintf functionnality. For fscanf functionnality, look at NSScanner.
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