Bug 20117
| Summary: | *printf manpage doesn't document %n | ||
|---|---|---|---|
| Product: | Documentation | Reporter: | xaa <xaa> |
| Component: | Books & Articles | Assignee: | freebsd-doc (Nobody) <doc> |
| Status: | Closed FIXED | ||
| Severity: | Affects Only Me | ||
| Priority: | Normal | ||
| Version: | Latest | ||
| Hardware: | Any | ||
| OS: | Any | ||
On Sun, 23 Jul 2000 10:31:25 +0200, xaa@dohd.org wrote: > I tried to look up the actions of printf("%n"), but it wasn't > in the manpage, only in the code I would urge anyone looking into this to examine the C standard before coming up with his own (possibly inferior) explanation. Ciao, Sheldon. The wise Sheldon Hearn produced the following lines: > On Sun, 23 Jul 2000 10:31:25 +0200, xaa@dohd.org wrote: > > > I tried to look up the actions of printf("%n"), but it wasn't > > in the manpage, only in the code > > I would urge anyone looking into this to examine the C standard before > coming up with his own (possibly inferior) explanation. > None around :-) But well, I felt guilty not giving at least some attempt to fix it when I PR'ed it -- Mark Huizer - xaa@timewasters.nl - xaa@dohd.cx - xaa@iae.nl If you're not in my dictionary, you're not in my universe. What would you like to be replaced with? (Clippy, the helpful paperclip) -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
After some looking, I found this documentation from the GNU libc
manual. Would this be acceptable?
The `%n' conversion is unlike any of the other output conversions.
It uses an argument which must be a pointer to an `int', but
instead of
printing anything it stores the number of characters printed so
far by
this call at that location. The `h' and `l' type modifiers are
permitted to specify that the argument is of type `short int *'
or
`long int *' instead of `int *', but no flags, field width, or
precision are permitted.
For example,
int nchar;
printf ("%d %s%n\n", 3, "bears", &nchar);
prints:
3 bears
and sets `nchar' to `7', because `3 bears' is seven characters
- -Jason
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The wise Jason M. Taylor produced the following lines:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> After some looking, I found this documentation from the GNU libc
> manual. Would this be acceptable?
>
> The `%n' conversion is unlike any of the other output conversions.
> It uses an argument which must be a pointer to an `int', but
> instead of
> printing anything it stores the number of characters printed so
> far by
> this call at that location. The `h' and `l' type modifiers are
> permitted to specify that the argument is of type `short int *'
> or
> `long int *' instead of `int *', but no flags, field width, or
> precision are permitted.
>
> For example,
>
> int nchar;
> printf ("%d %s%n\n", 3, "bears", &nchar);
>
> prints:
>
> 3 bears
>
> and sets `nchar' to `7', because `3 bears' is seven characters
>
Fine with me, as long as something is in the man pages :-)
Mark
State Changed From-To: open->closed iMy -current system has this in printf(3) n The number of characters written so far is stored into the inte- ger indicated by the ``int *'' (or variant) pointer argument. No argument is converted. As far as I can see, it's been there forever. The text is not quite as verbose as some of the suggested replacements, but I'm wary of lifting text directly from GPLd man pages and putting it in our base system. If you think the text isn't clear enough, please suggest a replacement (ideally, as a patch :-) ), and PR it. Thanks. |
I tried to look up the actions of printf("%n"), but it wasn't in the manpage, only in the code Fix: This is a lousy bit of description for what it does, but well, it's better than nothing. (Before Format:) Result type: An optional character that indicates the type of the value for use with format characters n, i, o, u and x. 'q' (or 'll') stands for a quad int, 'l' for a long int, 'h' for a short int. Int is default. In the format characters: n Returns the amount of characters output so far, including formating actions. Requires a pointer value to write the value to. Beware: this changes your parameter!