On Mon, Jan 25, 2016 at 12:23:01PM +0000, Rainer Weikusat wrote:
> KatolaZ <katolaz@???> writes:
>
> [...]
>
> > I still don't see the need for an internal buffer to print out a
> > formatted string, to be honest :)
>
> Everything in code can always be implemented in a number of different
> ways, hence, whatever the code ends up doing is "not really needed" ---
> it could have achieved the same in a different way.
>
> In this case, the function is part of a 79 lines program whose main
> looks like this:
>

> int main(int argc, char **argv)
> {
>     char const *name;
>     int status;

>

>     name = get_name(*argv);
>     openlog(name, LOG_PID | LOG_PERROR, LOG_DAEMON);
>     if (argc < 3) usage();

>

>     print_start(name, argv[1]);

>

>     switch (fork()) {
>     case -1:
>     die(__func__, "fork");

>

>     case 0:
>     execvp(argv[2], argv + 2);

>

>     syslog(LOG_ERR, "main: execvp: %m(%d)", errno);
>     _exit(1);
>     }

>

>     wait(&status);
>     print_stop(status);

>

>     return 0;
> }

>
> and whose purpose is to enable me to write
>

> starting "unleashed VPN" \
>     daemon -n chdir / monitor -n qvpn ssh-vpn mes-pgsql 5000 unleashed unleashed4

>
> in an init script to get a 'start: ok (or failed)' message printed to
> file descriptor 2 with having to put two printf invocation around the
> start command. And in the context of that, using stdio for the sole
> purpose of performing a trivial string formatting operation seemed very
> inappropriate --- that's new-fangled, ill-thought out stuff supposed to
> make UNIX(*) easier to use by moron^WUCB students and who really needs
> that?

I did not dispute your preference for not using stdio, but the choice
to copy strings into internal buffers just to change one character and
spit them on stdout. And in fact my 6-lines proposal for doing exactly
the same was:

void another_print_start(char *name, char *what){                                                                                     char c[3] = " :";                                                                                                                    c[2] = name[0] & ~0x20;                                                                                                              write(2, c+2, 1);                                                                                                                    write(2, name+1, strlen(name) -1);                                                                                                   write(2, c, 2);                                                                                                                      write(2, what, strlen(what));                                                                                                       }

You asked for comments, I commented that alloca was probably not
needed and potentially dangerous, and that you could achieve the same
with simpler code, but apparently you didn't like the comment :D


>
> The program also contains a very nice example of why the post-increment
> operators is useful (and I means 'useful', not 'common because of
> mindless copying of example code'):
>

> static char const *get_name(char const *arg0)
> {
>     char const *n, *r;

>

>     n = r = arg0;
>     while (*r) if (*r++ == '/') n = r;
>     return n;
> }

That's pretty straight-forward C-programming, IMHO, but I agree that
it could be seen as interesting by a mor^H^H^Hstudent who approaches C
for the first time.

Peace, love and hacking.

KatolaZ

--
[ Enzo Nicosia aka KatolaZ --- GLUG Catania -- Freaknet Medialab ]
[ me [at] katolaz.homeunix.net -- http://katolaz.homeunix.net -- ]
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