hello everyone

i want to input ip like a char,then split into "127 0 0 1"
so that i can scan ips for start ip to end ip.
I tried with strtok spliting but program crashes when i do

sprintf (buffer, "%s",pch[1]);

Could you please post the code you have. The information you've provided so far isn't enough to do anything more than take wild guesses.

#include <stdio.h>
#include <iostream.h>
#include <string.h>
int main ()
  char buffer [50];
  char buf[50];
  char * pch;

  cin >> buf;
pch = strtok (buf,".");
for (pch[3] = 1;pch[3] < 255;pch[3]++)
  sprintf (buffer, "%s.%s.%s.%s",pch[0],pch[1],pch[2],pch[3]);
  return 0;

I think this is an excellent use case for strtol. It allows you to provide an end marker that indicates where the last translation ended. For a well-formed (see note below) IP string, that is always going to be a period. Given that, you can construct something like:

#include <cstdio>
#include <cstdlib>

int main (int argc, char ** argv) {
    char * ip = argv[1], *next = 0;
    long quad[3] = {0};
    for (int i = 0; i < 3; ++i) {
        quad[i] = strtol (ip, &next, 10);
        ip = next + 1;
    for (int i = 1; i < 255; ++i)
        printf ("%d.%d.%d.%d\n", quad[0], quad[1], quad[2], i);
    return 0;

And it will parse the first three octets and generate a sequence of all addresses with a /24 mask. For example:

$ ./a.out

NOTE: It is up to you to verify well-formedness. My example elides much error checking for the sake of brevity.

yes i see that you are on linux.im on the windows and its the same program chrashes

I don't have access to a Windows build environment at the moment. Once I get to one I will try to reproduce the problem you are seeing.