On Sun, May 19, 2013 at 10:46:49PM +0200, Michael Kerrisk wrote:
Hi,
> On 05/12/13 22:22, Georg Sauthoff wrote:
> > the strtok man-page does not specify what happens if `str` does not
> > contain any `delim`iters.
> > If you don't already know strtok one might assume then either:
> > - the delimiter-less string is considered the next token and thus
> > returned upon the first call to strtok
> > - on the first call NULL is returned because there are not any tokens
> > Related issue: is the non-empty `str`-suffix after the last `delim`
> > returned as a token or not?
> Thanks for the report, though I must say that it would have been a
> little more helpful if you had answered the rhetorical questions you
> ask... (It would have aided me as I reminded myself of the details.)
oh, sorry, you are right.
> > I know how strtok works -
>
> In which case a patch would have made the bug report even better still!
Ok, next time.
> > but perhaps it makes sense to explicitly
> > address these issues in the Linux man page.
> Anyway, I agree that the page could be clearer. I've added the following text:
> A sequence of calls to strtok() that operate on the same string
> maintains a pointer that determines the point from which to
> start searching for the next token. The first call to strtok()
> sets this pointer to point to the first byte of the string.
> The start of the next token is determined by scanning forward
> for the next nondelimiter byte in str. If such a byte is
> found, it is taken as the start of the next token. If no such
> byte is found, then there are no more tokens, and strtok()
> returns NULL. (A string that is empty or that contains only
> delimiter will thus cause strtok() to return NULL on the first
plural, delimiters?
> call.)
>
> The end of each token is found by scanning forward until either
> the next delimiter byte is found or until the terminating null
> byte ('\0') is encountered. If a delimiter byte is found, it
> is overwritten with a null byte to terminate the current token,
> and strtok() saves a pointer to the following byte; that
> pointer will be used as the starting point when searching for
> the next token. In this case, strtok() returns a pointer to
> the start of the found token.
> From the above description, it follows thatt a sequence of two
typo: /thatt/that/
> or more contiguous delimiter bytes in the parsed string is con‐
> sidered to be a single delimiter, and that delimiter bytes at
> the start or end of the string are ignored. Put another way:
> the tokens returned by strtok() are always nonempty strings.
> Thus, for example, given the string "aaa;;bbb,", successive
> calls to strtok() that specify the delimiter string ";," would
> return the strings "aaa" and "bbb", and then a NULL pointer.
> Sufficient?
Yes!
Best regards
Georg
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