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passing ofstream reference

Dec 13, 2016 at 1:53pm
sk9294 (30)
i am trying to write a program that finds files in a folder recursively but i am not sure how to pass ofstream reference when i am running my program it runs successfully but when i open the file its empty ca someone please tell me where i am wrong.

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#include <iostream>
#include<fstream>
#include <dirent.h>
#include<string.h>
#include<cstdlib>
#include <sys/stat.h>

using namespace std;

    void browse(string addr,ofstream& outstream){
        DIR *dir;
        dirent *ent;
        struct stat buf;
        const char* caddr=addr.c_str();

        if ((dir = opendir (caddr)) != NULL){
            while ((ent = readdir (dir)) != NULL) {
                if((strcmp(ent->d_name,"..")==0)||(strcmp(ent->d_name,".")==0)){}
                else{
                    stat(ent->d_name,&buf);
                    if(S_ISREG(buf.st_mode)){outstream<<ent->d_name<<"\"\n";}
                    else if(S_ISDIR(buf.st_mode)){browse(addr+"\\"+ent->d_name,outstream);}
                    }

            }
        }
        else {cout<<"cannot open directory";}
        closedir (dir);
    }

int main()
{
  
    string addr="F:\\";
    ofstream outstream;
    outstream.open("c:\\files.txt",ios::app);
    browse(addr,outstream);
    outstream.close();
    return 0;
}
Edit & run on cpp.sh
Dec 13, 2016 at 2:04pm
Chervil (7320)
You are correctly passing the outstream by reference.
Perhaps there is an error in the logic.
Dec 13, 2016 at 2:27pm
jlb (4973)
but when i open the file its empty

Which file is empty?

Are you sure there are any regular files in the root of drive "F:"? Your program only appears to list the directories in the directory provided, it doesn't navigate to any other sub directories.
Dec 13, 2016 at 2:32pm
gunnerfunner (2127)
browse(addr+"\\"+ent->d_name,outstream
string addr (in main() ) already has the trailing double backslash, do you need another pair after this?
Last edited on Dec 13, 2016 at 2:32pm
Dec 13, 2016 at 3:28pm
sk9294 (30)
i edited it actually there was a folder name after f:\\
Dec 13, 2016 at 3:34pm
sk9294 (30)
i solved above problem i was passing just file address with stat, i replaced it with absolute address by adding addr to ent->d_name and it worked but now i am having another problem files present in the first child folder are not written in output file rest all files of other folder are being written i don't know what is happening
Dec 13, 2016 at 3:36pm
sk9294 (30)
i put a cout before outstream even that cout is showing files of first folder but on opening output file, files of first folder are not present.
Dec 13, 2016 at 3:42pm
sk9294 (30)
corrected code:

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#include <iostream>
#include<fstream>
#include <dirent.h>
#include<string.h>
#include<cstdlib>
#include <sys/stat.h>

using namespace std;

    void browse(string addr,ofstream& outstream){
        DIR *dir;
        dirent *ent;
        struct stat buf;
        outstream.open("C:\\files.txt",ios::app);
        const char* caddr=addr.c_str();
        cout<<caddr<<"\n\n\n";

        if ((dir = opendir (caddr)) != NULL){
            while ((ent = readdir (dir)) != NULL) {

                if((strcmp(ent->d_name,"..")==0)||(strcmp(ent->d_name,".")==0)){}
                else{
                    string pathname=addr+"\\"+ent->d_name;

                    const char* cfname=pathname.c_str();
                    
                    stat(cfname,&buf);

                    if(S_ISREG(buf.st_mode)){


                            outstream<<ent->d_name<<"\"\n";
                            cout<<ent->d_name<<"\"\n";
                    }
                    else if(S_ISDIR(buf.st_mode)){
                            //cout<<ent->d_name;
                            browse(addr+"\\"+ent->d_name,outstream);
                    }
                    }

            }
        }
        else {cout<<"cannot open directory";}
        outstream.close();
        closedir (dir);
    }
int main()
{


    /*DIR *dir;
    dirent *ent;*/
    string addr="F:\\Introduction";
    ofstream outstream;

    browse(addr,outstream);

    return 0;
}
Edit & run on cpp.sh
Dec 13, 2016 at 3:42pm
sk9294 (30)
still not showing files of first folder
Dec 13, 2016 at 4:26pm
gunnerfunner (2127)
Change the name associated with the ofstream object to a non-existing file instead of files.txt and see if that works. Also try and put in state flag checks throughout browse() and see if it generates any messages
Dec 13, 2016 at 5:59pm
sk9294 (30)
I opened ofstream inside browse function and it worked but it is not a good practice i guess, now ofstream is opened and closed every time browse function is called

Working Code


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#include <iostream>
#include<fstream>
#include <dirent.h>
#include<string.h>
#include<cstdlib>
#include <sys/stat.h>

using namespace std;

    void browse(string addr){
        DIR *dir;
        dirent *ent;
        struct stat buf;
        ofstream outstream1;
        outstream1.open("C:\\Users\\sk9294\\Desktop\\wierd.txt",ios::app);
        const char* caddr=addr.c_str();
        cout<<"\n\n"<<caddr<<"\n\n\n";

        if ((dir = opendir (caddr)) != NULL){
            while ((ent = readdir (dir)) != NULL) {

                if((strcmp(ent->d_name,"..")==0)||(strcmp(ent->d_name,".")==0)){}
                else{
                    string pathname=addr+"\\"+ent->d_name;

                    const char* cfname=pathname.c_str();

                    stat(cfname,&buf);

                    if(S_ISREG(buf.st_mode)){


                            outstream1<<ent->d_name<<"\n";
                            cout<<ent->d_name<<"\n";
                    }
                    else if(S_ISDIR(buf.st_mode)){
                          
                            browse(addr+"\\"+ent->d_name);
                    }
                    }

            }
        }
        else {cout<<"cannot open directory";}
        outstream1.close();
        closedir (dir);
    }
int main()
{


    
    string addr="F:\\Introduction";
   

    browse(addr);

    return 0;
}
Edit & run on cpp.sh
Dec 13, 2016 at 6:02pm
sk9294 (30)
I have never passed ofstream as reference before, can anybody help me change this code to pass ofstream reference from main, so that ofstream is opened and closed only once during program run.
Dec 13, 2016 at 6:13pm
Chervil (7320)
I have never passed ofstream as reference before, can anybody help me change this code to pass ofstream reference from main, so that ofstream is opened and closed only once during program run.

The very first post in this thread is an example, at least with regard to the ofstream.
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#include <iostream>
#include <fstream>

void browse(std::ofstream& outstream)
{
    outstream << "some text\n";
}

int main()
{
    std::ofstream outstream("c:\\files.txt");
    browse(outstream);
}
Edit & run on cpp.sh
Dec 14, 2016 at 4:06am
sk9294 (30)
yes but that very first program is giving weird output, it is not including all files in the directory. I ran that code for a directory having lots of folder and sub folders in it, although the cout listed all files but when i opened output file it had only one file name in it then i thought there must be some problem with the ofstream reference so i moved ofstream inside browse function and it started listing all files in the output file too.
Dec 14, 2016 at 5:37am
Chervil (7320)
Here, took the latest "Working Code" from this thread, reinstated the ofstream reference
(and some small mostly cosmetic adjustments)
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#include <iostream>
#include <fstream>
#include <dirent.h>
#include <cstring>
#include <string>
#include <cstdlib>
#include <sys/stat.h>

void browse(std::string addr, std::ofstream & outstream1)
{
    DIR *dir;
    dirent *ent;
    struct stat buf;

    std::cout << "\n\n" << addr << "\n\n\n";

    if ( (dir = opendir (addr.c_str())) )
    {
        while ( (ent = readdir (dir)) ) 
        {
            if ( strcmp(ent->d_name, "..") && strcmp(ent->d_name, ".")  )
            {
                std::string pathname = addr + "\\" + ent->d_name;

                stat(pathname.c_str(), &buf);

                if (S_ISREG(buf.st_mode))
                {
                    outstream1 << ent->d_name << "\n";
                    std::cout  << ent->d_name << "\n";
                }
                else if (S_ISDIR(buf.st_mode))
                {
                    browse(pathname.c_str(), outstream1);
                }
            }
        }
        
        closedir (dir);
    }
    else
    {
        std::cout << "cannot open directory";
    }
}

int main()
{
    std::string addr = "F:\\Introduction";
        
    std::ofstream fout("C:\\Users\\sk9294\\Desktop\\wierd.txt");
   
    browse(addr, fout);
}
Edit & run on cpp.sh
Dec 14, 2016 at 7:00am
Chervil (7320)
A slight variation. Essentially the same code as before, but with two changes.
1. defer the processing of subdirectory until after ordinary files
2. allow capture of console output to another file. 
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#include <iostream>
#include <fstream>
#include <dirent.h>
#include <cstring>
#include <string>
#include <cstdlib>
#include <sys/stat.h>
#include <vector>

std::string title(const std::string & text, size_t  width = 80)
{
    std::string result = ' ' + text + ' ';
    while (result.size() < width)
    {
        result = '-' + result;
        if (result.size() < width)
            result += '-';
    }
    return result;
    
}
void browse(std::string addr, std::ofstream & outstream1, std::ostream& logout=std::cout)
{
    DIR *dir;
    dirent *ent;
    struct stat buf;

    logout << "\n" << title(addr) << "\n\n";

    if ( (dir = opendir (addr.c_str())) )
    {
        std::vector<std::string> subdir;
        
        while ( (ent = readdir (dir)) ) 
        {    
            if ( strcmp(ent->d_name, "..") && strcmp(ent->d_name, ".")  )
            {
                std::string pathname = addr + "\\" + ent->d_name;
                stat(pathname.c_str(), &buf);

                if (S_ISREG(buf.st_mode))
                {
                    outstream1 << ent->d_name << "\n";
                    logout     << ent->d_name << "\n";
                }
                else if (S_ISDIR(buf.st_mode))
                {
                    subdir.push_back(pathname);
                    //browse(pathname.c_str(), outstream1, logout);
                }
            }
        }
        
        for (const std::string & p : subdir)
        {
            browse(p.c_str(), outstream1, logout);
        }
        
        closedir (dir);
    }
    else
    {
        logout << "cannot open directory";
    }
}

int main()
{
    std::string addr = "F:\\Introduction";
        
    std::ofstream fout("output.txt");
   
    // browse(addr, fout);  // default output to console
    
    std::ofstream log("logout.txt");
    browse(addr, fout, log);
    
}
Edit & run on cpp.sh


change last few lines to get console output:
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    browse(addr, fout);  // default output to console
    
    // std::ofstream log("logout.txt");
    // browse(addr, fout, log);
Last edited on Dec 14, 2016 at 7:57am
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