Parse the IP in a file, actually, it is not difficult

Question

Sasha Pachev · Accepted Answer

Solution in C++:

using namespace std;
#include 
#include 
#include 
#include 

typedef unsigned int uint;

static uint ip2num(const char* buf)
{
  uint res = 0, b = 0;
  for (; *buf;)
  {
    char c = *buf++;

    if (c == '.')
    {
      res = (res << 8) + b;
      b = 0;
    }
    else if (isdigit(c))
    {
      b = b * 10 + (c - '0');
    }
    else
      return (res << 8) + b;
  }

  return (res << 8) + b;
}

int main(int argc, char** argv)
{
  if (argc < 2)
  {
    cerr << "Missing file argument" << endl;
    exit(1);
  }

  ifstream is(argv[1]);

  if (!is)
  {
    cerr << "Error opening file" << endl;
    exit(1);
  }

  for (;;)
  {
    char buf[32];
    is.getline(buf, sizeof(buf));

    if (!is)
      break;

    cout << "ip " << buf << " decimal represenation is " << ip2num(buf) << endl;
  }

  return 0;
}

Anonymous · Answer

Quick guess in Perl

open "filename.txt" || die
while :
    $string ~= /\d+\.\d+\.\d+\.\d+/
    print $string

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