problem with atoi(char to int)

[ritvik]

i have to read values from a text file which contains 4 inetegrs and 3 two-dimensional arrays.
i have written a code to read 2 integer values and one single dimensional array, but it gives all values as 0. even with get() function it does not read anything.
this is my code:

#include <fstream.h>
#include <stdlib.h>

void read(fstream &t, int *i1,int *i2,char *i3);

void main()
{
int l,m,i;
char *jmp;

fstream myfile;
myfile.open("test_data.txt",ios::in||ios::out);
myfile<<"4";
myfile<<"2";
myfile<<"3";
myfile<<"2";
read(myfile,&l,&m,jmp);
cout<<"no of lots "<<l<<endl;
cout<<"no of eds lines "<<m<<endl;
cout<<"order for each line " <<endl;
cout<<jmp;
myfile.close();
}

void read(fstream &myfile, int *i1,int *i2,char *i3)
{
char temp,temp1;
myfile.get(temp);
cout<<"temp = "<<temp<<endl;
*i1 = atoi(&temp);
myfile>>temp1;
*i2 = atoi(&temp1);
myfile>>i3;
}

please tell me the error

[plemoine]

What about reviewing your usage of your file handle? First, you use it to pipe in data, then to read it back at *the position where you were at*.
What about closing your file just before reopening it for reading? You may rewind the data as an alternative.

i have to read values from a text file which contains 4 inetegrs and 3 two-dimensional arrays.
i have written a code to read 2 integer values and one single dimensional array, but it gives all values as 0. even with get() function it does not read anything.
this is my code:

#include <fstream.h>
#include <stdlib.h>

void read(fstream &t, int *i1,int *i2,char *i3);

void main()
{
int l,m,i;
char *jmp;

fstream myfile;
myfile.open("test_data.txt",ios::in||ios::out);
myfile<<"4";
myfile<<"2";
myfile<<"3";
myfile<<"2";
read(myfile,&l,&m,jmp);
cout<<"no of lots "<<l<<endl;
cout<<"no of eds lines "<<m<<endl;
cout<<"order for each line " <<endl;
cout<<jmp;
myfile.close();
}

void read(fstream &myfile, int *i1,int *i2,char *i3)
{
char temp,temp1;
myfile.get(temp);
cout<<"temp = "<<temp<<endl;
*i1 = atoi(&temp);
myfile>>temp1;
*i2 = atoi(&temp1);
myfile>>i3;
}

please tell me the error

[archonmagnus]

i have to read values from a text file which contains 4 inetegrs and 3 two-dimensional arrays.
i have written a code to read 2 integer values and one single dimensional array, but it gives all values as 0. even with get() function it does not read anything.
this is my code:

#include <fstream.h>
#include <stdlib.h>

void read(fstream &t, int *i1,int *i2,char *i3);

void main()
{
int l,m,i;
char *jmp;

fstream myfile;
myfile.open("test_data.txt",ios::in||ios::out);
myfile<<"4";
myfile<<"2";
myfile<<"3";
myfile<<"2";
read(myfile,&l,&m,jmp);
cout<<"no of lots "<<l<<endl;
cout<<"no of eds lines "<<m<<endl;
cout<<"order for each line " <<endl;
cout<<jmp;
myfile.close();
}

void read(fstream &myfile, int *i1,int *i2,char *i3)
{
char temp,temp1;
myfile.get(temp);
cout<<"temp = "<<temp<<endl;
*i1 = atoi(&temp);
myfile>>temp1;
*i2 = atoi(&temp1);
myfile>>i3;
}

please tell me the error

Try something like this. I don't guarantee it to work, but it theoretically should.

#include <iostream>
#include <fstream>
#include <string>
 
using namespace std;
 
void write (void);
void read (ifstream &myfile, int *i1, int *i2, string *i3);
 
int main (void)
{
    int l, m;
    string jmp;
 
    write();
 
    ifstream myfile ("test_data.txt", ios::in);
 
    read(myfile, &l, &m, &jmp);
 
    cout<<"Number of Lots:      "<<l<<endl
        <<"Number of eds Lines: "<<m<<endl
        <<"Order for Each Line: "<<endl
        <<"       "<<jmp<<endl;
 
    myfile.close();
 
    return 0;
}
 
void write (void)
{
    ofstream output ("test_data.txt", ios::out);
 
    output<<"4232";
 
    output.close();
 
    return;
}
 
void read (ifstream &myfile, int *i1, int *i2, string *i3)
{
    char temp = 0, temp1 = 0;
 
    myfile>>temp;
    cout<<"Temp = "<<temp<<endl;
    *i1 = atoi(&temp);
 
    myfile>>temp1;
    cout<<"Temp1 = "<<temp1<<endl;
    *i2 = atoi(&temp1);
 
    myfile>>*i3;
 
    return;
}
 

As was previously stated, you'll need to close the output file before re-opening it for reading. Since (I assume) you are more interested in reading an existing file, that part can be taken out easily. This uses strings, which can easily be converted into a character array.

[ritvik]

hey thank you both.
yes i needed to revise my file concepts. it is working now
can you people help me with anotehr problem. can i directly read an array or do i have to read it char by char and then store in array one by one

[weaknessforcats]

yes i needed to revise my file concepts. it is working now
can you people help me with anotehr problem. can i directly read an array or do i have to read it char by char and then store in array one by one

By definition an array elements must occupy contiguous memory locations. Therefore, you can write an array to disc by just writing the correct nuymber of bytes. And you can read it back by reading the correct number of bytes and storing them at the location of element 0.