Question

I am wondering how to go through a text file and locate a given word (“foobar”) at different locations within each line but then realign the word to the same position in a new text file, let me know if this doesn’t make sense.

***in text file***
1 foobar baz
2  foobar baz
3   foobar baz

****out text file***
1     foobar baz
2     foobar baz
3     foobar baz

Answer 1

The io manipulator std::setw() from can be used to create fixed-length columns in text output, and std::setfill() is used to specify the fill character:

std::cout << std::setw(5) << std::setfill('0') << 5 << std::endl;

Will print:

00005

This can easily be used to create a small program which reads all lines from one file and writes them to another file and at the same time aligns all columns (in the below program >> is used to read one column, which means that the columns in the in file are supposed space-separated, by one or more whitespace characters):

#include <iostream>
#include <iomanip>
#include <vector>
#include <fstream>
#include <map>
#include <algorithm>

int main (int argc, char* arv[])
{
   using namespace std;

   std::vector<std::vector<std::string> > records;
   std::map<int, int> column_widths;

   std::ifstream in_file("infile.txt", std::ios::text);
   if (!in_file.is_open())
       return 1;

   std::ofstream out_file("outfile.txt", std::ios::text);
   if (!out_file.is_open())
       return 2;

   // read all the lines and columns into records
   std::string line;
   while (std::getline(in_file, line)) {
       std::istringstream is(line);
       std::vector<std::string> columns;
       std::string word;
       int column_index = 0;
       while (is >> word) {
           columns.push_back(word);
           column_widths[column_index] = std::max(column_width[column_index], word.length());
           ++column_index;
       }

       records.push_back(columns);
   }

   // now print all the records and columns with fix widths
   for (int line = 0; line < records.size(); ++line) {
       const std::vector<std::string>& cols = records[line]; 
       for (int column = 0; column < cols.size(); ++column) {
           out_file << std::setw(column_widths[column])
                    << std::setfill(' ')
                    << cols[column] << ' ';
       }
       out_file << "\n";
   }

   return 0;
}

I didn’t compile the program but it should work :).