help with renumbering entries in record file

[Snej-coder]

-----First example-----

1,firstguy,hispassword
2,nextguy, hispassword

------------------



i want to change numbers here and add a 10000 to front of them so it would read

100001,firstguy,hispassword
100002,nextguy, hispassword




-------- 2nd example -------
1, A_name, 4 , more data, etc
----------------------------------------------------------------

i want to change first and second numbers here and add a 10000 to front of them so it would read



100001, A_name, 100004, more data, etc


Note:


this is going to be on a large scale with hundreds of records to change to that kind of thing
here is my lame code that doesn't work. take a look at it if you can solve this problem that would be really cool.
thanks for looking

#include <fstream>
#include <iostream>

using namespace std;

int main()
{
    ifstream infile;
    ofstream outfile;
    string mystring;
    infile.open("in.txt");
    outfile.open("out.txt");
    
    
while(infile)
{
    infile.getline(mystring);
    outfile.write("10000");
    outfile.write(mystring);
        
}
    outfile.close();
    infile.close();
return 0;
}

[dwks]

You can read a line like this (or read the whole thing and use stringstreams to parse it -- see the FAQ):

while(file >> number >> comma >> name >> comma >> password) {
}

Also see this tutorial. http://www.cprogramming.com/tutorial/lesson10.html

[Snej-coder]

thanks! ill try that

[dwks]

Actually, I didn't realize that your problem was so simple. You could get away with

#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main()
{
    ifstream infile;
    ofstream outfile;
    string mystring;
    infile.open("in.txt");
    outfile.open("out.txt");
    
    
while(!infile.eof())
{
    infile.getline(mystring);
    outfile.write("10000");
    outfile.write(mystring);
        
}
    outfile.close();
    infile.close();
return 0;
}

You should also use .is_open() to see if the files were opened correctly.

[edit] Never mind, you were using the wrong functions and I didn't notice . . . maybe something more like

#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
    ifstream infile("in.txt");
    ofstream outfile("out.txt");
    string mystring;
    
    while(!infile.eof()) {
        getline(infile, mystring);
        outfile << "10000" << mystring << endl;
    }
    
    outfile.close();
    infile.close();
    return 0;
}

[/edit]

[vart]

if getline failed - the loop will exit only on the next iteration...

while(getline(infile, mystring))
{
        outfile << "10000" << mystring << endl;
}

maybe better

[Daved]

>> while(!infile.eof())
This is a bad suggestion, as it can cause the last line to be processed twice. The OP's version was better, vart's version is best if you use getline.

>> while(file >> number >> comma >> name >> comma >> password) {
However, I like this suggestion best overall and better than using getline. Write the data back out with

outfile << number+100000 << ',' << name << ',' << password;

This is better because it scales to the second problem more easily.

[dwks]

I don't know what I was thinking with the while(!eof) . . . I had stuck that in, meaning to change it, and forgot to do so. That's what happens when you're in a hurry.

>> while(file >> number >> comma >> name >> comma >> password) {
However, I like this suggestion best overall and better than using getline.

It's difficult to handle errors with that sort of setup, however.

Perhaps the best solution of all would be a hybrid, something like this:

#include <sstream>
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
    ifstream infile("in.txt");
    ofstream outfile("out.txt");
    string mystring;
    string name, password;
    int number;
    char comma;
    
    while(getline(infile, mystring)) {
        istringstream ss(mystring);
        ss >> number >> comma >> name >> comma >> password;
        outfile << number+100000 << ',' << name << ',' << password;
    }
    
    outfile.close();
    infile.close();
    return 0;
}

It needs some error handling, of course. Like checking that the characters read from ss into comma really are commas, and seeing if the files could be opened.

[Daved]

>> It's difficult to handle errors with that sort of setup, however.
Your stringstream solution doesn't really handle the errors much better. You'd want to check the return value of the read from the stringstream.

I don't think the stringstream is necessary, though. It's benefit is that if one row is incorrectly formatted it will continue to process other rows. If you want to handle invalid rows without the string stream you just have to separate the read from the while control and then clear(), ignore() and continue if it fails. If you're sure the file is properly formatted that isn't even necessary.

[Snej-coder]

#include <sstream>
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
    ifstream infile("in.txt");
    ofstream outfile("out.txt");
    string mystring;
    string name, password;
    int number;
    char comma;
    
    while(getline(infile, mystring)) {
        istringstream ss(mystring);
        ss >> number >> comma >> name >> comma >> password;
        outfile << number+100000 << ',' << name << ',' << password << endl;
    }
    
    outfile.close();
    infile.close();
    return 0;
}

ok so i added an endl to the outfile thing but when i run the program i get
"100001,firstguy,hispassword100002,nextguy,hispass word"
as my output so why would it ignoring the endl and not skip a line in the output file?

[dwks]

D'oh, it's reading the name as "firstguy,hispassword", leaving nothing for the password. You can't just use the istringstream >> operator to get the name and the password, or if you do, you can't separate them out.

[Snej-coder]

well i wrote it wrong before the way it appears in the file is like

1 , username , password
2 , username , password

and

1 , username , 4 , data , moredata <---its seperated by a space then a comma then another space " , "

thats what you were wondering about right cause in the file its not set up like
1,username,password
but like
1 , username , password

ok well hope that helps and thanks again for helping me with this program!

[dwks]

Right, that makes things easier . . . this works for me:

#include <sstream>
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
    ifstream infile("in.txt");
    ofstream outfile("out.txt");
    string mystring;
    char name[80], password[80];
    int number;
    char comma1, comma2;
    
    while(getline(infile, mystring)) {
        istringstream ss(mystring);
        if(ss >> number >> comma1 >> name >> comma2 >> password
            && comma1 == ',' && comma2 == ',') {
            
            outfile << number + 100000 << " , " << name << " , " << password
                << endl;
        }
        else {
            clog << "Error processing line: " << mystring << endl;
        }
    }
    
    outfile.close();
    infile.close();
    return 0;
}

The output is

$ cat in.txt
1 , john , pass
2 , sam , word

$ ./test2

$ cat out.txt
100001 , john , pass
100002 , sam , word

$

[Snej-coder]

thanks again for the help! ok well i can modify your code to fit the extra collums that ill need for the 2nd example and i think that im good now oh what does

char name[80];

exatcly mean btw?

[dwks]

Oops . . . it should be a string. Those are old-style C-strings. You shouldn't use them. And I should proof-read my code more carefully before posting it . . .

http://www.cprogramming.com/tutorial/lesson9.html

[ZuK]

oh what does

char name[80];

exatcly mean btw?

reserve space for an array of 80 characters and call it name.
Kurt