Replace every other occurrence of pattern

Wynd · 11-17-2005, 02:57 PM

How can I use sed (or anything else) to replace every other occurrence of a pattern?

Tinkster · 11-17-2005, 03:06 PM

Examples always help ...
Before:

After:

Cheers,
Tink

Wynd · 11-17-2005, 03:23 PM

Sorry. Here's a quick one, replacing every other "foo" with "bar":

Before:
foo foo foo foo foo foo

After:
foo bar foo bar foo bar

Wynd · 11-17-2005, 05:21 PM

Nevermind, I just wrote a C++ program to do it.

Dankles · 11-17-2005, 06:11 PM

I would like to know a solution to this problem if any one has it.
also, wynd, could you post your source code in addition to any other replies?

Tinkster · 11-17-2005, 06:44 PM

Code:

awk '{for(i=2;i<=NF;i+=2){sub("foo","bar",$i)};print}' file

Cheers,
Tink

Dankles · 11-17-2005, 07:25 PM

Quote:

Originally posted by Tinkster

Code:

awk '{for(i=2;i<=NF;i+=2){sub("foo","bar",$i)};print}' file

Cheers,
Tink

Nice work, thanks!

Wynd · 12-14-2005, 03:27 PM

Quote:

Originally Posted by Dankles

I would like to know a solution to this problem if any one has it.
also, wynd, could you post your source code in addition to any other replies?

Sorry for the delay but I just saw this post now. I don't know if this is the best/most efficient code, but it did what I wanted.

Code:

#include <iostream>
#include <fstream>
using namespace std;

int main(int argc, char** argv)
{
    ifstream fin;
    bool bSwitch = false;
    char cInput;

    fin.open(argv[1]);

    if (!fin.is_open())
    {
        cerr << "Error: Could not open file " << argv[1] << endl;
    }
    else
    {
        while (!fin.eof())
        {
            fin.get(cInput);

            if (cInput == '\"') // Character to look for
            {
                if (bSwitch == false)
                {
                    cout << '^'; // Replace with something else
                }
                else
                {
                    cout << '\"'; // Print out unchanged
                }

                bSwitch = !bSwitch;
            }
            else
            {
                cout << cInput;
            }
        }

        cout << endl;
    }

    return 0;
}

Dankles · 12-14-2005, 03:43 PM

Thanks for the code. I'll let you know how it works.