The difference between strtol() and strtoul() ?

Interestingly, I note that strtoul() accepts strings that begin with a sign
(+ or -).  This is odd, since you'd (*) think that a sign (particularly, a
minus) would be a syntax error in parsing for an unsigned value.

Further, although the (Linux) man page is more than a bit murky on the
subject, it seems that the result of parsing, say, "-1", with strtoul() is
the largest unsigned value (usually, 2**N-1 or a lot of F's (in hex)).
Whereas, I would expect it to be 1 (i.e., just take the absolute value).

Comments?  I find this all very counterintuitive.

(*) Or should I say, "one would" ?

P.S.  Why isn't there a strtoi() or strtou() ?  I know, of course, that
there is atoi(), but that doesn't have the error checking capability that
the strto* functions have.

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