code in c++

hi to all

I use the following code in c++ under linux, but I need to convert it to c under linux, any one can convert it from c++ to c.

the details of the program is:
It reads a text file and then asks the user to enter a string.
It then displays how many times the string occurs and also prints the lines in which it occurs

Code:

#include<map>
#include<iostream>
#include<string>
#include<fstream>
#include<sstream>
using std::istringstream;
using std::ifstream;
using std::string;
using std::cout;
using std::cin;
using std::cerr;
using std::map;
using std::multimap;
int main()
{
    multimap<string,int> words;
    map<int,string> lines;
    string str;
    ifstream input("test.txt");
    if(input.fail())
    {
        cerr<<"\nThe file could not be opened.";
        return -1;
    }
    int i=1;
    while(getline(input,str))
    {
        istringstream in(str);
        string s;
        while(in>>s)
        {
            words.insert(make_pair(s,i));
        }
        lines.insert(make_pair(i,str));
        i++;
    }
    string search;
    cout<<"\nEnter a word to search: ";
    cin>>search;
    cout<<"\nThe number of matches = "<<words.count(search)<<'\n';
    multimap<string,int>::iterator it1=words.lower_bound(search);
    multimap<string,int>::iterator it2=words.upper_bound(search);
    while(it1!=it2)
    {
        int x=it1->second;
        map<int,string>::iterator iter=lines.find(x);
        cout<<'\n'<<x<<" ) "<<iter->second<<'\n';
        it1++;
        while(true)
        {
            if(it1!=it2 && it1->second==x)
            {
                it1++;
 
            }
            else
            {
                break;
            }
        }
    }
    return 0;
}

thanks in advance

 

You're pretty much going to have to rewrite it from scratch; this code uses a lot of C++ specific syntax all of which is invalid in C. However the C++ code is overcomplicated, you can do it in about quarter the code, and it will be a lot faster as well; just use fgets and strstr (which you could also do in C++, there's no need for this silly multimap stuff and reading the whole file into memory at the start).

print greeting
get string
if fopen
- while !eof
- - get string from file
- - test match with strstr
- - - if it matches add 1 to a count and display the line
- - (handle multiple matches if you need to)
- end while
end if
display the count

If you need to display the count THEN the matching lines, just loop over the file twice; this will be a lot easier than trying to store the matching lines in memory (and will scale to massive files, thus turning that horrendous demonstration of how NOT to write C++ code into a utility that might actually be useful).