Re: Command Languages Versus Programming Languages

Liste des GroupesRevenir à cu shell 
Sujet : Re: Command Languages Versus Programming Languages
De : cross (at) *nospam* spitfire.i.gajendra.net (Dan Cross)
Groupes : comp.unix.shell comp.unix.programmer comp.lang.misc
Date : 22. Nov 2024, 19:12:34
Autres entêtes
Organisation : PANIX Public Access Internet and UNIX, NYC
Message-ID : <vhqhii$d5e$1@reader2.panix.com>
References : 1 2 3 4
User-Agent : trn 4.0-test77 (Sep 1, 2010)
In article <87o727rwga.fsf@doppelsaurus.mobileactivedefense.com>,
Rainer Weikusat  <rweikusat@talktalk.net> wrote:
Something which would match [0-9]+ in its first argument (if any) would
be:
>
#include "string.h"
#include "stdlib.h"
>
int main(int argc, char **argv)
{
   char *p;
   unsigned c;
>
   p = argv[1];
   if (!p) exit(1);
   while (c = *p, c && c - '0' > 10) ++p;
   if (!c) exit(1);
   return 0;
}
>
but that's 14 lines of text, 13 of which have absolutely no relation to
the problem of recognizing a digit.
>
This is wrong in many ways.  Did you actually test that program?
>
First of all, why `"string.h"` and not `<string.h>`?  Ok, that's
not technically an error, but it's certainly unconventional, and
raises questions that are ultimately a distraction.
>
Such as your paragraph above.
>
Second, suppose that `argc==0` (yes, this can happen under
POSIX).
>
It can happen in case of some piece of functionally hostile software
intentionally creating such a situation. Tangential, irrelevant
point. If you break it, you get to keep the parts.
>
Third, the loop: why `> 10`? Don't you mean `< 10`?  You are
trying to match digits, not non-digits.
>
Mistake I made. The opposite of < 10 is > 9.

I see.  So you want to skip non-digits and exit the first time
you see a digit.  Ok, fair enough, though that program has
already been written, and is called `grep`.

Fourth, you exit with failure (`exit(1)`) if `!p` *and* if `!c`
at the end, but `!c` there means you've reached the end of the
string; which should be success.
>
Mistake you made: [0-9]+ matches if there's at least one digit in the
string. That's why the loop terminates once one was found. In this case,
c cannot be 0.

Ah, you are trying to match `[0-9]` (though you're calling it
`[0-9]+`).  Yeah, your program was not at all equivalent to one
I wrote, though this is what you posted in response to mine, so
I assumed you were trying to emulate that behavior (matching
`^[0-9]+$`).

But I see above that you mentioned `[0-9]+`.  But as I mentioned
above, really you're just matching any digit, so you may as well
be matching `[0-9]`; again, this not the same as the actual
regexp, because you are ignoring the semantics of what regular
expressions actually describe.

In any event, this seems simpler than what you posted:

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
        if (argc != 2) {
                fprintf(stderr, "Usage: matchd <str>\n");
                return EXIT_FAILURE;
        }

        for (const char *p = argv[1]; *p != '\0'; p++)
                if ('0' <= *p && *p <= '9')
                        return EXIT_SUCCESS;

        return EXIT_FAILURE;
}

- Dan C.


Date Sujet#  Auteur
29 Mar 24 * Command Languages Versus Programming Languages708Lawrence D'Oliveiro
29 Mar 24 +- Re: Command Languages Versus Programming Languages1candycanearter07
29 Mar 24 +* Re: Command Languages Versus Programming Languages19Janis Papanagnou
29 Mar 24 i+* Re: Command Languages Versus Programming Languages15Lawrence D'Oliveiro
30 Mar 24 ii`* Re: Command Languages Versus Programming Languages14Janis Papanagnou
30 Mar 24 ii +* Re: Command Languages Versus Programming Languages3Janis Papanagnou
30 Mar 24 ii i`* Re: Command Languages Versus Programming Languages2Keith Thompson
30 Mar 24 ii i `- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 ii +* Re: Command Languages Versus Programming Languages6Lawrence D'Oliveiro
30 Mar 24 ii i+* Re: Command Languages Versus Programming Languages3Keith Thompson
30 Mar 24 ii ii`* Re: Command Languages Versus Programming Languages2Lawrence D'Oliveiro
30 Mar 24 ii ii `- Re: Command Languages Versus Programming Languages1Keith Thompson
30 Mar 24 ii i`* Re: Command Languages Versus Programming Languages2Janis Papanagnou
30 Mar 24 ii i `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
30 Mar 24 ii +* Re: Command Languages Versus Programming Languages3Keith Thompson
30 Mar 24 ii i`* Re: Command Languages Versus Programming Languages2Janis Papanagnou
30 Mar 24 ii i `- Re: Command Languages Versus Programming Languages1Keith Thompson
31 Mar 24 ii `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
29 Mar 24 i`* Re: Command Languages Versus Programming Languages3Stefan Ram
30 Mar 24 i `* Re: Command Languages Versus Programming Languages2Janis Papanagnou
30 Mar 24 i  `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
29 Mar 24 +* Re: Command Languages Versus Programming Languages168Muttley
29 Mar 24 i+- Re: Command Languages Versus Programming Languages1Josef Möllers
29 Mar 24 i+* Re: Command Languages Versus Programming Languages9Richard Kettlewell
29 Mar 24 ii`* Re: Command Languages Versus Programming Languages8Muttley
29 Mar 24 ii `* Re: Command Languages Versus Programming Languages7Kaz Kylheku
29 Mar 24 ii  `* Re: Command Languages Versus Programming Languages6Muttley
29 Mar 24 ii   `* Re: Command Languages Versus Programming Languages5Kaz Kylheku
30 Mar 24 ii    `* Re: Command Languages Versus Programming Languages4Muttley
30 Mar 24 ii     +- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 ii     `* Re: Command Languages Versus Programming Languages2Kaz Kylheku
1 Apr 24 ii      `- Re: Command Languages Versus Programming Languages1Muttley
29 Mar 24 i`* Re: Command Languages Versus Programming Languages157John Ames
29 Mar 24 i +* Re: Command Languages Versus Programming Languages155Muttley
29 Mar 24 i i+- Re: Command Languages Versus Programming Languages1John Ames
29 Mar 24 i i+* Re: Command Languages Versus Programming Languages149Kaz Kylheku
29 Mar 24 i ii`* Re: Command Languages Versus Programming Languages148Muttley
29 Mar 24 i ii +* Re: Command Languages Versus Programming Languages146Kaz Kylheku
29 Mar 24 i ii i+* Re: Command Languages Versus Programming Languages4David W. Hodgins
29 Mar 24 i ii ii+* Re: Command Languages Versus Programming Languages2Johanne Fairchild
30 Mar 24 i ii iii`- Re: Command Languages Versus Programming Languages1David W. Hodgins
30 Mar 24 i ii ii`- Re: Command Languages Versus Programming Languages1Janis Papanagnou
30 Mar 24 i ii i`* Re: Command Languages Versus Programming Languages141Muttley
30 Mar 24 i ii i `* Re: Command Languages Versus Programming Languages140Kaz Kylheku
1 Apr 24 i ii i  `* Re: Command Languages Versus Programming Languages139Muttley
1 Apr 24 i ii i   +* Re: Command Languages Versus Programming Languages137Johanne Fairchild
1 Apr 24 i ii i   i`* Re: Command Languages Versus Programming Languages136Muttley
1 Apr 24 i ii i   i +- Re: Command Languages Versus Programming Languages1Kaz Kylheku
2 Apr 24 i ii i   i `* Re: Command Languages Versus Programming Languages134Johanne Fairchild
2 Apr 24 i ii i   i  +* Re: Command Languages Versus Programming Languages113ram@zedat.fu-berlin.de (Stefan Ram)
2 Apr 24 i ii i   i  i+* Re: Command Languages Versus Programming Languages111Stefan Ram
2 Apr 24 i ii i   i  ii+* Re: Command Languages Versus Programming Languages109Stefan Ram
3 Apr 24 i ii i   i  iii`* Re: Command Languages Versus Programming Languages108Lawrence D'Oliveiro
3 Apr 24 i ii i   i  iii `* Re: Command Languages Versus Programming Languages107David Brown
3 Apr 24 i ii i   i  iii  +- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
3 Apr 24 i ii i   i  iii  +- Re: Command Languages Versus Programming Languages1John Ames
3 Apr 24 i ii i   i  iii  `* Re: Command Languages Versus Programming Languages104Keith Thompson
3 Apr 24 i ii i   i  iii   +* Re: Command Languages Versus Programming Languages99Richard Kettlewell
4 Apr 24 i ii i   i  iii   i+- Re: Command Languages Versus Programming Languages1Muttley
4 Apr 24 i ii i   i  iii   i`* Re: Command Languages Versus Programming Languages97Stefan Ram
5 Apr 24 i ii i   i  iii   i `* Re: Command Languages Versus Programming Languages96Lawrence D'Oliveiro
5 Apr 24 i ii i   i  iii   i  +* Re: Command Languages Versus Programming Languages49Muttley
5 Apr 24 i ii i   i  iii   i  i+* Re: Command Languages Versus Programming Languages3candycanearter07
5 Apr 24 i ii i   i  iii   i  ii`* Re: Command Languages Versus Programming Languages2Muttley
6 Apr 24 i ii i   i  iii   i  ii `- Re: Command Languages Versus Programming Languages1candycanearter07
6 Apr 24 i ii i   i  iii   i  i`* Re: Command Languages Versus Programming Languages45Lawrence D'Oliveiro
6 Apr 24 i ii i   i  iii   i  i `* Re: Command Languages Versus Programming Languages44Alan Bawden
6 Apr 24 i ii i   i  iii   i  i  +* Re: Command Languages Versus Programming Languages13Lawrence D'Oliveiro
8 Apr 24 i ii i   i  iii   i  i  i`* Re: Command Languages Versus Programming Languages12John Ames
9 Apr 24 i ii i   i  iii   i  i  i `* Re: Command Languages Versus Programming Languages11Lawrence D'Oliveiro
9 Apr 24 i ii i   i  iii   i  i  i  +* Re: Command Languages Versus Programming Languages9John Ames
9 Apr 24 i ii i   i  iii   i  i  i  i`* Re: Command Languages Versus Programming Languages8Richard Kettlewell
9 Apr 24 i ii i   i  iii   i  i  i  i +* Re: Command Languages Versus Programming Languages2Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i  i  i i`- Re: Command Languages Versus Programming Languages1Richard Kettlewell
9 Apr 24 i ii i   i  iii   i  i  i  i `* Re: Command Languages Versus Programming Languages5David Brown
9 Apr 24 i ii i   i  iii   i  i  i  i  `* Re: Command Languages Versus Programming Languages4Lawrence D'Oliveiro
9 Apr 24 i ii i   i  iii   i  i  i  i   `* Re: Command Languages Versus Programming Languages3David Brown
10 Apr 24 i ii i   i  iii   i  i  i  i    `* Re: Command Languages Versus Programming Languages2Lawrence D'Oliveiro
10 Apr 24 i ii i   i  iii   i  i  i  i     `- Re: Command Languages Versus Programming Languages1Kaz Kylheku
9 Apr 24 i ii i   i  iii   i  i  i  `- Re: Command Languages Versus Programming Languages1Kaz Kylheku
6 Apr 24 i ii i   i  iii   i  i  +* Re: Command Languages Versus Programming Languages3Kaz Kylheku
6 Apr 24 i ii i   i  iii   i  i  i`* Re: Command Languages Versus Programming Languages2David Brown
6 Apr 24 i ii i   i  iii   i  i  i `- Re: Command Languages Versus Programming Languages1Muttley
6 Apr 24 i ii i   i  iii   i  i  +- Re: Command Languages Versus Programming Languages1candycanearter07
6 Apr 24 i ii i   i  iii   i  i  `* Re: Command Languages Versus Programming Languages26Muttley
7 Apr 24 i ii i   i  iii   i  i   +* Re: Command Languages Versus Programming Languages22Alan Bawden
8 Apr 24 i ii i   i  iii   i  i   i`* Re: Command Languages Versus Programming Languages21Muttley
8 Apr 24 i ii i   i  iii   i  i   i `* Re: Command Languages Versus Programming Languages20David Brown
8 Apr 24 i ii i   i  iii   i  i   i  `* Re: Command Languages Versus Programming Languages19Muttley
8 Apr 24 i ii i   i  iii   i  i   i   +* Words to the wise (Was: Command Languages Versus Programming Languages)2Kenny McCormack
8 Apr 24 i ii i   i  iii   i  i   i   i`- Re: Words to the wise (Was: Command Languages Versus Programming Languages)1Muttley
8 Apr 24 i ii i   i  iii   i  i   i   `* Re: Command Languages Versus Programming Languages16Kaz Kylheku
8 Apr 24 i ii i   i  iii   i  i   i    +* Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)9Kenny McCormack
9 Apr 24 i ii i   i  iii   i  i   i    i`* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)8Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i   i    i +- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1D
9 Apr 24 i ii i   i  iii   i  i   i    i `* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)6candycanearter07
9 Apr 24 i ii i   i  iii   i  i   i    i  `* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)5Janis Papanagnou
9 Apr 24 i ii i   i  iii   i  i   i    i   +- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1candycanearter07
10 Apr 24 i ii i   i  iii   i  i   i    i   `* Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)3Lawrence D'Oliveiro
10 Apr 24 i ii i   i  iii   i  i   i    i    +- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1Chris Elvidge
10 Apr 24 i ii i   i  iii   i  i   i    i    `- Re: Phrases that should be banned on Usenet (Was: Command Languages Versus Programming Languages)1candycanearter07
9 Apr 24 i ii i   i  iii   i  i   i    `* Re: Command Languages Versus Programming Languages6Muttley
8 Apr 24 i ii i   i  iii   i  i   +- [meta] Re: Command Languages Versus Programming Languages1Janis Papanagnou
10 Apr 24 i ii i   i  iii   i  i   `* Re: Command Languages Versus Programming Languages2Keith Thompson
5 Apr 24 i ii i   i  iii   i  `* Re: Command Languages Versus Programming Languages46Janis Papanagnou
3 Apr 24 i ii i   i  iii   `* Re: Command Languages Versus Programming Languages4David Brown
2 Apr 24 i ii i   i  ii`- Re: Command Languages Versus Programming Languages1Kaz Kylheku
2 Apr 24 i ii i   i  i`- Re: Command Languages Versus Programming Languages1Kaz Kylheku
2 Apr 24 i ii i   i  `* Re: Command Languages Versus Programming Languages20Lawrence D'Oliveiro
1 Apr 24 i ii i   `- Re: Command Languages Versus Programming Languages1Lawrence D'Oliveiro
1 Apr 24 i ii `- Re: Command Languages Versus Programming Languages1Andreas Eder
29 Mar 24 i i+- Re: Command Languages Versus Programming Languages1Christian Weisgerber
30 Mar 24 i i+* Re: Command Languages Versus Programming Languages2David Brown
30 Sep 24 i i`- Re: Command Languages Versus Programming Languages1Bozo User
29 Mar 24 i `- Re: Command Languages Versus Programming Languages1Kaz Kylheku
29 Mar 24 +* Re: Command Languages Versus Programming Languages510Johanne Fairchild
29 Mar 24 +* Re: Command Languages Versus Programming Languages2David Brown
30 Mar 24 +* Re: Command Languages Versus Programming Languages3Dmitry A. Kazakov
30 Sep 24 `* Re: Command Languages Versus Programming Languages4Bozo User

Haut de la page

Les messages affichés proviennent d'usenet.

NewsPortal