Question

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

 int main(){
 ifstream infile;
 ofstream outfile;
 infile.open("oldfile.txt");
 outfile.open("newfile.txt");
 while(infile){
    string str,nstr;
    infile>>str;
    char charr[10];
    charr[0]='<';charr[1]='\0';
    nstr=str.substr(0,str.find_first_of(charr));

    outfile<<nstr<<' ';
 }
}

this program uses substr(0, string.find_first-of(charcter array which is starting point to be substring))each word’s unnecessary sub strings but it doesn’t preserve the line number when writing to another file. can you fix it . it writes the file word by word sequencially. the code didn’t preserve line by line,

Answer 1

string input doesn’t care about line boundaries, it treats \n,\t,\v and probably others the same as space.

#include <sstream>
#include <iostream>
#include <string>
using namespace std;

int main()
{
    string line,word;
    char foo[] = "<";
    while ( getline(cin,line) ) {
        string newline;
        for ( istringstream words(line)
            ; words >> word ; ) {
                newline+=word.substr(0,word.find_first_of(foo))+' ';
        }
        cout << newline << '\n';
    }
}