Read - Write CSV Files in C++

However, this is a better way,

#include <iostream>
#include <iomanip>
#include <fstream>
#include <vector>
#include <string>

using namespace std;

int main()
{
      ifstream in("test.csv");
      vector < vector <string> > data;
      string element, delimiters = ",";
      int row = 0;
      char ch;

      data.push_back( vector <string>() );

      while( in.read( (char*)&ch, 1 ) )
      {
            if( ch == '\n' || ch == '\r' )
            {
                  data.push_back( vector <string>() );
                  row++;
            }
            else if( delimiters.find_first_of(ch) == delimiters.npos )
            {
                  element += ch;
            }
            else
            {
                  data[row].push_back( element );
                  element = "";
            }
      }

      in.close();

      for( unsigned int x = 0; x < data.size(); x++ )
      {
            for( unsigned int y = 0; y < data[x].size(); y++ )
            {
                  cout << data[x][y] << ",";
            }
            cout << endl;
      }

      return 0;
}

Exceter

Is the problem happening because some of the data contains commas? If it does, then you will need to make sure that for those items at least, they are "contained" in some way, say between double quotes. Then, you'll need to adapt your algorithm to correctly read in the whole item, ignoring any commas that it contains. The other way you could do it is to "escape" the commas that are part of the data, in much the same way as string literals escape quote characters.

Hope this helps!

BabyhueyHN?

Thanks for the code, It worked great. I didn't understand some of it , but it worked.

You are most welcome. Indicate the sections you do not understand and I'll do my best to explain them.

Cheers!
Exceter

Exceter,
      You code works to display the data in the fields between the delimiters. However, I need to be able to manipulate the data in those fields in order to combine parts of strings in different fields. Should I post this as a new question or can you tell me how I should do it. I have tried strncpy and strncat to no avail. Thanks, Don

>> I need to be able to manipulate the data in those fields in order to combine parts of strings in different fields.

That's no problem. The fields are read into std::string. Therefore, all you have to do to extract/insert data into the given field is to access it via operator[] and use the assignment operator to insert/remove data. For example,

string s = data[0][0]; // Place the first field from the first row into s
data[0][0] = "Testing..."; // Set the first field to the string literal, "Testing..."

You can then write the vector out to file in roughly the same manner you printed it to the screen. Alternatively, you can use char arrays if you want, but I wouldn't. For example,

char s[25];
strcpy( s, data[0][0].c_str() ); // Copy the first field into s

...

data[0][0] = s; // Copy the value back into the vector

Exceter

Here, I took a few minutes and threw this together(who knows; I may find it usefull in the future).

-- csv.h --

#ifndef CSV_H
#define CSV_H

#include <iomanip>
using std::endl;

#include <fstream>
using std::ifstream;
using std::ofstream;

#include <string>
using std::string;

#include <vector>
using std::vector;

class csv
{
      friend bool operator==( const csv &, const csv & );
      friend bool operator!=( const csv &, const csv & );

      public:
            csv();
            csv( char* );
            void read( char* );
            void write( char* );
            string getfield( int, int );
            void setfield( int, int, string );
            const csv &operator=( const csv & );
            int rows, cols;

      private:
            vector < vector <string> > data;
};

csv::csv()
{
      rows = cols = 0;
      data.push_back( vector <string>() );
}

csv::csv( char* fname )
{
      read( fname );
}

const csv &csv::operator=( const csv &n )
{
      rows = n.rows;
      cols = n.cols;
      data = n.data;

      return *this;
}

void csv::read( char* fname )
{
      ifstream in( fname );
      string element, delimiters = ",\n\r";
      char ch;

      rows = cols = 0;
      data.clear();

      data.push_back( vector <string>() );

      while( in.read( (char*)&ch, 1 ) )
      {
            if( delimiters.find_first_of(ch) == delimiters.npos )
                  element += ch;

            else
            {
                  if( ch != '\r' )
                  {
                        data[rows].push_back( element );
                        element = "";
                        if( ch == '\n' )
                        {
                              data.push_back( vector <string>() );
                              rows++;
                        }
                  }
            }
      }

      in.close();
      data[rows].push_back( element );
      cols = data[0].size();
      rows = data.size();
}

void csv::write( char* fname )
{
      ofstream out( fname );

      for( int x = 0; x < rows; x++ )
      {
            for( int y = 0; y < cols; y++ )
            {
                  out << data[x][y];
                  if( y != cols - 1 )
                        out << ",";
            }
            out << endl;
      }

      out.close();
}

string csv::getfield( int x, int y )
{
      return data[x][y];
}

void csv::setfield( int x, int y, string val )
{
      data[x][y] = val;
}

bool operator==( const csv &d1, const csv &d2 )
{
      return d1 == d2;
}

bool operator!=( const csv &d1, const csv &d2 )
{
      return d1 != d2;
}

#endif

-- test.cpp --

#include <iostream>
#include <iomanip>
#include "csv.h"

using namespace std;

int main()
{
      csv mycsv("test.csv");
      mycsv.setfield(0,0,"testing");
      mycsv.write("test1.csv");

      return 0;
}

Hopefully, this should make dealing with the csv file much easier.

Exceter

>> csv::csv()
>> {
>>     rows = cols = 0;
>>     data.push_back( vector <string>() );
>> }

This would cause problems, that should have been,

csv::csv()
{
    rows = cols = 0;
}

Exceter

Exceter,

     I am still having problems getting the program to allow me to manipulate the data. Can I send you the file, to show you the problem. Thanks

Post the code and the file, if necessary, and I'll be glad to help.

I'm trying to make TestCsv.cpp (works with idsNew.csv datafile) program to manipulate characters in fields one and
two i.e. break the fields and combine 1 charcater from field 1, 3 characters from field2 and last 4 characters of field 3.
The program codeWstring.cpp(idsNew.txt data file) does exactly what I need with the fields,  but it does not read a comma-delimited file.  Thanks for all your help. Thanks, Don
 
_____________________________________________

// codeWstring.cpp  -

#include <iostream>
#include <iomanip>
#include <fstream>
#include <vector>
#include <string>
#include<iomanip>
using namespace std;
#include<ctype.h>      //can only find ctype.h
//using std::setiosflags;
//using std::resetiosflags;
//void idText(idCharPart, fName, lName);

void main()
{
    ifstream in("idsNew.csv");
      ofstream outFileCsv("ids.csv");
      ofstream outTxt("ids.txt");
    vector < vector <string> > data;
    string element, delimiters = ",\n\r";
//      char string1[5], string2[5], idCharPart[5] = {""} ;
      int ssn;
      string campus;
      int uniqueId=1000001, tempId;

    int row = 0;
    char ch;

    data.push_back( vector <string>() );

    while( in.read( (char*)&ch, 1 ) )
    {

         if( delimiters.find_first_of(ch) == delimiters.npos )
         {
              element += ch;
         }
         else
         {
              if( ch != '\r' )
              {
                   data[row].push_back( element );
                   element = "";

                   if( ch == '\n' )
                   {
                        data.push_back( vector <string>() );
                        row++;
                   }
              }
         }

    }

    if( element.size() > 0 )
         data[row].push_back( element );
            
    in.close();

    for( unsigned int x = 1; x < data.size(); ++x )
            
    {        
            for( unsigned int y = 0; y < data[x].size(); y++ )
         {
                    outFileCsv<< data[x][y] << ",";
                    cout<<data[x][y] << ",";

                    typedef char string[20];          // I need to manipulate my strings
                    string fName, lName, idCharPart;  //  i.e. to break and combine them,  
                    if (y == 0)                       // but no metter what I try it does not work :(
                    {
                        fName = data[x][y];
                    }
                    if (y == 1)
                    {
                        lName = data[x][y];
                    }
                  strncpy(idCharPart, fName, 1);
                  idCharPart[1] = '\0';
            
                  strncat(idCharPart, lName,3);

                  if(strlen(idCharPart) < 4)
                        strcat(idCharPart, "_");

                  idCharPart[0] = tolower(idCharPart[0]);
                  idCharPart[1] = tolower(idCharPart[1]);
                  idCharPart[4] = '\0';
//                    idText(idCharPart, string1, string2);
            }
            
            tempId = uniqueId % 10000;

            outFileCsv<<idCharPart<<setw(4)<<setfill('0')<<tempId<<","<<uniqueId<endl;
            cout<<idCharPart<<setw(4)<<setfill('0')<<tempId<<","<<uniqueId<<endl;

            uniqueId++;
    }
}
/*
void idText(string idCharPart, string fName, string lName)
{  
            char filler[2] = {"_"};

            strncpy(idCharPart, fName, 1);
            idCharPart[1] = '\0';
            
            strncat(idCharPart, lName,3);

            if(strlen(idCharPart) < 4)
                  strcat(idCharPart, filler);

            idCharPart[0] = tolower(idCharPart[0]);
            idCharPart[1] = tolower(idCharPart[1]);
            idCharPart[4] = '\0';
}
*/
__________________________________________________

//  TestPrWorks.cpp

#include <iostream.h>
#include <fstream.h>
#include <string.h>
#include <iomanip.h>
#include<ctype.h>
void idText(char idCharPart[], char fName[], char lName[]);

int main()
{
      ifstream inFile("idsNew.txt");
      ofstream outFile("idsOut.txt");
      ofstream outFileCsv("idsOutTemp.csv");
//      char fName[15], lName[18], idCharPart[5] = {""}, major[5], filler[2] = {"_"};
      char fName[15], lName[18], idCharPart[5] = {""}, major[5];  //if with fumction

      char ssn[10], campus[5];
      int tempId = 1, uniqueID = 1000001;

      outFileCsv<<"f_name"<<","<<"l_name"<<","<<"SSN"<<","<<"campus"<<","<<"id"<<endl;

      while(inFile)
      {
            inFile>>fName>>lName>>ssn>>campus>>major;  
            idText(idCharPart, fName, lName);

             tempId = uniqueID % 10000;

            outFileCsv<<fName<<","<<lName<<","<<ssn<<","<<campus<<","
                        <<idCharPart<<setw(4)<<setfill('0')<<tempId<<endl;
            cout<<fName<<","<<lName<<","<<ssn<<","<<campus<<","
                  <<idCharPart<<setw(4)<<setfill('0')<<tempId<<endl;

            uniqueID = uniqueID+1;
      }
}

void idText(char idCharPart[], char fName[], char lName[])
{  
            char filler[2] = {"_"};

            strncpy(idCharPart, fName, 1);
            idCharPart[1] = '\0';
            
            strncat(idCharPart, lName,3);

            if(strlen(idCharPart) < 4)
                  strcat(idCharPart, filler);

            idCharPart[0] = tolower(idCharPart[0]);
            idCharPart[1] = tolower(idCharPart[1]);
            idCharPart[4] = '\0';
}

_____________________________________________________

idsNew.csv  File

John,Dow,123456789,1,BUAD
Henry,Tester,987654321,1,DPRP
Crapoita,O'Conner,123456788,1,LA
Julie,Abdul,123456787,1      BSOC
Muhammad,Abb-Alkehm,546465654,1,DPRN
Daniel,Aba,323156544,1,EGR
Jen,Yu,789654213,1,DPRN
_____________________________________________________
idsNew.txt File

John Dow 123456789 1 BUAD
Henry Tester 987654321 1 DPRP
Crapoita OConner 123456788 1 LA
Julie Abdul 123456787 1 BSOC
Muhammad AbbAlkehm 546465654 1 DPRN
Daniel Aba 323156544,1,EGR
Jen Yu 789654213 1 DPRN


*I had to take all the spaces ' . and - out of the names manually to get it to work because I cannot use those in the creation of the names and I can't figure out how to automatically get rid of them.

What should the output look like?

The output should look like:
Fname,Lname,SSN,Campus,Code,UID,UName
John,Dow,123456789,1,BUAD,1000001,jdow0001

The biggest problem is that in the CSV file we have to take the - / spaces / ' and .  out of the csv file becasue we cannot maniputate the data in the fields.

CSV File Example  John,Yu Pan,123456789,1,BUAD
Output should be John,Yu Pan,123456789,1,BUAD,1000001,jyup0001

CSV File Example  John,O'Conner,987654321,1,DPRS
Output should be John,O'Conner,987654321,1,DPRS,1000002,joco0002

CSV File Example  John,Hu,542136555,1,ECO
Output should be John,Hu,542136555,1,ECO,1000003,jhu_0003


We cannot preserve the name John,Yu Pan we must change it to John,YuPan manually for the program to work. The same is true for last names of o'Conner etc. If a last name has only 2 characters then we assign an _ for the third character.

I would like to assign data[x][y] to an array of chars in order to break data [x][y] and create a new field with the elements of data [x][y]. I need to be able to manipulate the data and have it ignore certain characters (',.,-, spaces) etc... So I can create the correct ID's . Thanks, Don

dynamic string objects that can be freely exchanged with standard char* types (so there is no need to change function calls nor the implementation when you change from char* to String (and vice versa)).  I think thats what I need.

>> I would like to assign data[x][y] to an array of chars in order to break data [x][y] and create a new field with the elements
>> of data [x][y].

You can do that by saying,

char st[50];
strcpy( st, data[x][y].c_str() );

Well, you can strip out the unwanted characters with the following function,

string removechars( string st, string delim )
{
    string result = "";

    for( unsigned int x = 0; x < st.length(); x++ )
    {
         if( delim.find_first_of( st[x] ) == delim.npos )
             result += st[x];
    }
    return result;
}

All you have to do is pass it the string which you want the characters removed from and a second string containing the characters to be removed. For example,

string st = ( "This i's a test...", " '." );
cout << st << endl;

-- output --
Thisisatest

>> dynamic string objects that can be freely exchanged with standard char* types (so there is no need to change function
>> calls nor the implementation when you change from char* to String (and vice versa)).

Go with std::string. It can be exchanged freely with char* types. When you want to call a function that accepts a char* with text contained in an instance of std::string all you have to say is,

myfunc( mystring.c_str() ); // c_str() returns a char* pointer to the text within the string object

I'll get back to you on the other stuff as soon as I can.

Note: That class I posted has a bug or two. If I can find the time to debug it, I'll post a new version.

Exceter

hello  Exceter

i try your code for CSV, am having error with
friend bool operator==( const csv &, const csv & );
friend bool operator!=( const csv &, const csv & );

if i comment them away it is fine. Actually can u tell me
what is the main purpose for the operator methods??..
u created..

Hi neele,

I created the != and == operators so you could compare two csv files if you wanted. You'd load a csv file into one instance of the class and another csv file into another instance of the class. You could then determine whether they were equal or not by saying,

if( file1 == file2 ) // If the csv files are equal, do whatever
{
    // etc...
}

if( file1 != file2 ) // If the csv files are not equal, do whatever
{
    // etc...
}

Exceter

Oh i see :) for that purpose..
But i am having compile error, only commenting away this 2 line will be ok
friend bool operator==( const csv &, const csv & );
friend bool operator!=( const csv &, const csv & );

so how to edit it so there isn't any compilation error.
Thanks exceter.

Could you post the offending code and the errors?

warning C4786: 'std::vector<std::vector<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::allocator<std::basic_string<char,std::char_traits<char>,std::allocator<char> > > >,std::allocator<s
td::vector<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::allocator<std::basic_string<char,std::char_traits<char>,std::allocator<char> > > > > >' : identifier was truncated to '255' characters in the debug information

error C2593: 'operator ==' is ambiguous
error C2593: 'operator !=' is ambiguous

That the error and warning messages...
By the way when i build (after commenting away the error lines)
I will have abt 30 warnings..due to the std::vector..

Any suggestions? or y i having those warning.
Thanks a lot !

Could you post the code that is giving you the errors?

Have you tried compiling your code in release mode?

Hello Exceter

I just tried to compile in release mode ..previously i using debug mode.
Yeah..it works..no more warnings...:D thanks !

But can i ask what the diff to compile in debug/release mode?
actually i am fairly new..in c++

and i know why i having the 'operator !=' is ambiguous,
as i try to print out some values using cout
thus i added using namespace std; causing the error.
Any idea how to allow me to use cout, getline IF i really need it together
with your code? so it won't have confilcts? i did try append std :: getline..
is that the best way out? Thanks once again

Hello Exceter ...

need some help..i am compiling your code on MAC..
but it seem that MAC cannot recognise \r\n??
as the output is only "testing" in the file output ;c

can u advise ...thanks..

I never use MACs.

>> but it seem that MAC cannot recognise \r\n??

Sorry, that is OS specific code. Windows use a CR/LF pair to indicate the end of a line. I'm not sure what MAC uses. Have you tried a plain old '\n' ?

Exceter

Hello.. Exceter

it works already now. Guess is OK already is my issue..;c
din place the file at the correct directory of mac..as i
am new..to tat as well ;o
But ya mac n win have different \r\n ..
i also unsure correct or not, yet to fully test the code..if there
is anything i will post again Thanks !