How can I divide this ipv6 address use to sscanf in c?

Question

For example , I want to separate this address.

http://[1fff:0:a88:85a3::ac1f]:8001/index.html

like..

    protocol = http
    address = 1fff:0:a88:85a3::ac1f
    port = 8001
    path = index.html

So I used this sscanf code.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>

void main()
{
//    char url[128] = "http://10.1.35.1:8088/inedex.htm";
    char url[128] = "http://[1fff:0:a88:85a3::ac1f]:8001/index.html";
    char url_6[128], port[10], path[40];

    char *tok, *cp, *host, *proto, /**port, *path,*/ *tok6;
    char *hostbuf, *portbuf, *buf;
    int c, len, ulen, cnt_6 = 0;
    struct in6_addr result;

    ulen = strlen(url);
    len = ulen *2 + 10 + 3;

    if(strncmp(url, "http://[", 8) == 0)
    {
        tok = &url[8];
        tok[-4] = '\0';
        proto = url;
        sscanf(tok, "%2000[^]]:%s", url_6, path);

        if(inet_pton(AF_INET6, url_6, &result))
        {
            printf("successful ipv6 address\n");
        }
        else
        {
            printf("Invalid ipv6 address\n");
        }
        printf("path= %s\n", path);
        printf("tok = %s\n", tok);
    }
}

But I don't understand this line.

sscanf(tok, "%2000[^]]:%s", url_6, path); //this line is okay.

Actually, it's the first time, I'm writing this line.

//port and path is pointer.... *port, *path...
sscanf(tok, "%2000[^]]:%10[^/]%s", url_6, port, path);

but when I debug this line, then segmentation fault accurs.... What did I do wrong ?
please answer this question.

thanks.

Did you consider [strtok](http://en.cppreference.com/w/c/string/byte/strtok)? — rocambille, Aug 03 '16 at 07:53
of course. but.. this sscanf isbetter than strtok to this parsing.. i think . do you have better idea on this? — kara, Aug 03 '16 at 08:00
Don't do [`void main()`](http://stackoverflow.com/questions/204476/what-should-main-return-in-c-and-c) — StoryTeller - Unslander Monica, Aug 03 '16 at 08:23

score 2 · Accepted Answer · edited Aug 03 '16 at 09:13

2

What you did wrong is twofold:

You specify maximum widths to sscnaf which are larger than your buffers.
You don't tell sscanf to consume your delimiters after you reach them (] and /).

So a somewhat fixed version (with your clutter removed, and main made standard conforming):

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

int main(void)
{
    char url[128] = "http://[1fff:0:a88:85a3::ac1f]:8001/index.html";
    char url_6[128], port[10], path[40];

    char *tok;

    if(strncmp(url, "http://[", 8) == 0)
    {
        tok = &url[8];
        tok[-4] = '\0';
        //sscanf(tok, "%2000[^]]:%s", url_6, path);
        sscanf(tok, "%127[^]]]:%9[^/]/%39s", url_6, port, path);
        //                   ^^      ^- delim '/' consumed here
        //                   |+- delim ':' consumed here
        //                   +- delim ']' consumed here

        printf("path= %s\n", path);
        printf("port= %s\n", port);
        printf("url_6 = %s\n", url_6);
    }

    return 0;
}

See it live here.

edited Aug 03 '16 at 09:13

kara

43
8

answered Aug 03 '16 at 09:05

StoryTeller - Unslander Monica

165,132
21
377
458

@kara, please stop editing my post to add elements irrelevent to the question you asked. This isn't the place to showcase your program, it answers how to get rid of the segmentation fault. – StoryTeller - Unslander Monica Aug 03 '16 at 09:19
OMG! Sorry i didnt know that. – kara Aug 03 '16 at 15:09
@kara, no worries. You seem to be fairly new to SO. So have a quick read [here](http://stackoverflow.com/help) – StoryTeller - Unslander Monica Aug 03 '16 at 15:14
Thanks to helping me ! ^^! – kara Aug 04 '16 at 00:48

How can I divide this ipv6 address use to sscanf in c?

1 Answers1