Re: Buffer contents well-defined after fgets() reaches EOF ?

On Sat 2/8/2025 10:23 PM, Andrey Tarasevich wrote:

 Note also that `fgets` is not permitted to assume that the limit value (the second parameter) correctly describes the accessible size of the buffer. E.g. for this reason it is not permitted to zero-out the buffer before reading. For example, this code is valid and has defined behavior
    char buffer[10];
   fgets(buffer, 1000, f);
 provided the current line of the file fits into `char[10]`. I.e. even though we "lied" to `fgets` about the limit, it is still required to work correctly if the actual data fits into the actual buffer.

... and this part of specification effectively guarantees, that any [tail] portion of the buffer not overwritten by the characters obtained from file, will remain unchanged. If `fgets` reads 5 characters from the file, only first 6 characters of the buffer will be overwritten, while the rest is guaranteed to remain untouched. If `fgets` reads nothing (instant end-of-file), the entire buffer remains untouched.
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Best regards,
Andrey