array of ofstreams

**quick** · 08-12-2005

ok i need to make an array of outfile file streams that will make about 16 different files. the files need to be named like funcfile0, funcfile1, funcfile2, etc. all the way to funcfile15. the name of the 'funcfile' part will be a char array input from the user. so i set char funcfile[15]; and then cin >> funcfile.

so my question is creating an array of ofstream that will open the desired files. once i have created all 16 of the files, i need to write different data to each of the files. i currently have a for loop set up to change the file that it writes to and it will increment the file name after writing each file.

here is what my code looks like now and it will compile but when i run it, it will crash when its writing the first file.

Code:

for(int ct=0;ct<16;ct++){
    ofstream funcf[ct];
    funcf[ct].open (funcfile+ct);
    if(funcf[ct].is_open()){
    cout << "writing function file" << ct<< " ..."<<endl;
    int c1=0;
    funcf[ct] << setw(10)<<idim<<setw(10)<<jdim<<setw(10)<<kdim<<setw(10)<<"6"<<endl;  
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){funcf[ct]<<endl;c1=0;}
    funcf[ct] << xmagE[e1][e2][e3]*sin(pi*xphsE[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << ymagE[e1][e2][e3]*sin(pi*yphsE[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << zmagE[e1][e2][e3]*sin(pi*zphsE[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}    
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << xmagH[e1][e2][e3]*sin(pi*xphsH[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << ymagH[e1][e2][e3]*sin(pi*yphsH[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << zmagH[e1][e2][e3]*sin(pi*zphsH[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}} 
    }   
    
    funcf[ct] << endl;
    funcf[ct].close();
}

**pianorain** · 08-12-2005

Code:

for(int ct=0;ct<16;ct++){
    ofstream funcf[ct];
    funcf[ct].open (funcfile+ct);
    if(funcf[ct].is_open()){

I bet funcfile is a character pointer. If so, then you can't do + to append an integer on the end. That actually increments the character pointer.

Also, your declaration of ofstreams should be outside your for loop. Look at what happens on your first pass through.

Code:

ct = 0;
   ofstream funcf[0]; //a zero-member array...sounds dangerous

**quick** · 08-12-2005

ahh ok yeah you're right that seemed to get the ball rolling but it will crash when writing the third file. and looking at the files that it creates. it will just take the name of the file and subtract a character. so i input the output file to test and it would creat 'test', 'est', 'st', 't' and then crash. so you're saying that has to do with when i was creating the type for the funcfile name.
i did char funcfile[15];
how would i fix this so it creates the correct file names? use a string?

here is my updated code:

Code:

ofstream funcf[15];
    for(int ct=0;ct<16;ct++){
    funcf[ct].open(funcfile+ct);
    if(funcf[ct].is_open()){
    cout << "writing function file" << ct<< " ..."<<endl;
    int c1=0;
    funcf[ct] << setw(10)<<idim<<setw(10)<<jdim<<setw(10)<<kdim<<setw(10)<<"6"<<endl;  
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){funcf[ct]<<endl;c1=0;}
    funcf[ct] << xmagE[e1][e2][e3]*sin(pi*xphsE[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << ymagE[e1][e2][e3]*sin(pi*yphsE[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << zmagE[e1][e2][e3]*sin(pi*zphsE[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}    
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << xmagH[e1][e2][e3]*sin(pi*xphsH[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << ymagH[e1][e2][e3]*sin(pi*yphsH[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}}
    c1=0;
    for(int e3=0;e3<idim;e3++){
            for(int e2=0;e2<jdim;e2++){
                    for(int e1=0;e1<kdim;e1++){
    if(c1 == 3){ funcf[ct]<<endl;c1=0;}
    funcf[ct] << zmagH[e1][e2][e3]*sin(pi*zphsH[e1][e2][e3]/180.0+ct*pi/8.0)<<"       "; c1++;}}} 
    }   
    
    funcf[ct] << endl;
    funcf[ct].close();
}

**orbitz** · 08-12-2005

ofstream funcf[15];

I thought you wanted 16 files, not 15.

**quick** · 08-12-2005

yes i do want 16 files but i thought i could use element 0-15 to get 16 files. anyways the real trouble im having is the naming of the files.
funcf[ct].open(funcfile+ct);
that line is incorrect i think. the program names the files in an odd way that will subtract a character from the name each time it iterates through them. how do i write that statement so it will create the filename properly? funcfile is a char array. do i need to use some special function?

**pianorain** · 08-12-2005

Originally Posted by quick

it will just take the name of the file and subtract a character. so i input the output file to test and it would creat 'test', 'est', 'st', 't' and then crash.

Heh, you mean like I said here:

Originally Posted by pianorain

I bet funcfile is a character pointer. If so, then you can't do + to append an integer on the end. That actually increments the character pointer.

Yes, I would use strings and an ostringstream. Consider this:

Code:

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

using std::cout;
using std::endl;
using std::string;
using std::ostringstream;

int main()
{
	string a("awesome");
	ostringstream ost;
	ost << a << 10;
	cout << ost.str() << endl;
	return 0;
}

**quick** · 08-12-2005

ok so how do i append the file number on the end of the string?
so will create string funcfile;
have the use input the name of the funcfile.
so then when i go to open the files, do i just do something like:
funcf[ct].open ("funcfile"+ct); or what? im still unsure how to append the filenumber.

thanks

**pianorain** · 08-12-2005

In the above code example, I'm appending 10 onto awesome, resulting in "awesome10". Try a similar approach.

**~~ILoveVectors~~** · 08-12-2005

how bout this, i dont understand why you need an array?

Code:

string filename;
		stringstream ss;
		for(int i = 1; i != 10001; i++)
		{
			ss << "FILENAME" << i << ".txt" << flush;
			ss >> filename;
			file1.open(filename.c_str(), ios::out);
			if(file1.is_open())
			{
				file1 << "I smoke crack!" << endl;
				file1.close();
			}
			filename.clear();
			ss.clear();
		}

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