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strpbrk

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Join Date: Sep 2006

Posts: 63

Reputation: rowly is an unknown quantity at this point

Solved Threads: 3

rowly

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strpbrk

Apr 10th, 2007

hey guyz, i'm trying to search each ar for matching characters in the buff, but I seem to be getting a buffer overflow. Can anyone give me any pointers, any help would be appreciated, this is my code:

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 C Syntax (Toggle Plain Text) 
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
 
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
    for (i=0;i<ab;i++)
  { 
 
   pch[i] = strpbrk (ar[i],buff);
    printf ("%c ",pch[i]);
    pch[i] = strpbrk (pch[i],buff);
  }
 
}
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
  
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
    for (i=0;i<ab;i++)
  { 
    
   pch[i] = strpbrk (ar[i],buff);
    printf ("%c ",pch[i]);
    pch[i] = strpbrk (pch[i],buff);
  }
 
}

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Join Date: Aug 2005

Posts: 15,662

Reputation: Ancient Dragon has a reputation beyond repute

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Ancient Dragon Ancient Dragon is offline

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Re: strpbrk

Apr 10th, 2007

not buffer overflow -- you are not checking that strpbrk() returns a NULL pointer, which it can if the string does not contains the characters.

pch is a 2d array of pointers, so if strpbrk() returns NULL that printf will fail. The format specification in printf() is incorrect too -- should be "%s", not "%c" because pch[i] is a pointer to a string, not a single character.

Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.

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Join Date: Sep 2006

Posts: 63

Reputation: rowly is an unknown quantity at this point

Solved Threads: 3

rowly

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Re: strpbrk

Apr 10th, 2007

still getting the same thing...

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
 
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
   while (pch[i] != NULL)
  {    pch[i] = strpbrk (ar[i], buff);
    printf ("%s " , pch[i]);
    pch[i] = strpbrk (pch[i]+1,buff);
  } }
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
 
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
   while (pch[i] != NULL)
  {    pch[i] = strpbrk (ar[i], buff);
    printf ("%s " , pch[i]);
    pch[i] = strpbrk (pch[i]+1,buff);
  } }

Last edited by rowly; Apr 10th, 2007 at 2:18 pm. Reason: syntax error

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Join Date: Aug 2005

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Ancient Dragon Ancient Dragon is offline

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Re: strpbrk

Apr 10th, 2007

you have not changed anything. you have to check for NULL AFTER calling strpbrk(), not before. And you also created an infinite loop because the value of i counter is never changed.

>>pch[i]+1
that is wrong -- why are you adding 1 to a pointer value????

Last edited by Ancient Dragon; Apr 10th, 2007 at 3:35 pm.

Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.