Ubuntu - issue with opening a .txt file from terminal

Question

I have built a .cpp program in order to write some content to a .txt file created within the .cpp file.

I manage to write the desired content, however, when I am trying to open the created file from terminal, it says that it cannot find it although it is there.

When I try to open it with vi or nano it's content it's empty. It is like creating a new file.

However, when I open it outside terminal, I can see its content as I wanted.

What could be the problem and how can I fix this situation?

Bellow, I have added the code.

The problem is with the system(buffer) command. I receive the following error: sh: cannot open video2.txt: No such file. I have tried to opened the files from command prompt and I get the above described situation.

int main(int argc,char* argv[])
{

fstream RawStipFile;
RawStipFile.open(strcat(argv[1],".txt"));
string line;

if (RawStipFile.is_open())
{

    getline(RawStipFile, line);
    int i = 0;
    ofstream OutVideoStip;
    ofstream VideoList;
    VideoList.open("VideoList.txt");
    while ( RawStipFile.good() )
    {

        getline (RawStipFile,line);
        char* l;
        l = (char*) malloc(sizeof(char));
        l[0]=line[0];
        //cout<<line[0]<<endl;
        if (line[0]==35)
        {

            if (OutVideoStip.is_open())
            {
                OutVideoStip.close();
            }
            i++;
                        //char* base;
                        //base = (char*) malloc(1000*sizeof(char));
                        //sprintf(base, "%d", i);
            char* b;
            b = &line[1];
            VideoList<<b<<endl;
            OutVideoStip.open(strcat(b, ".txt"));


        }

        else
        {

            OutVideoStip << line << endl;

        }


    }

    OutVideoStip.close();
    RawStipFile.close();
    VideoList.close();
}

else
{
    cout << "Unable to open file \n";
}

fstream VideoNames;
VideoNames.open("VideoList.txt", fstream::in);

if (VideoNames.is_open())
{
    while ( VideoNames.good() )
    {
        getline(VideoNames, line);
        line=line.substr(1,line.length());
        if (line.compare(""))
        {
            string initial = "./txt2mat<";
            initial.append(line);
            initial.append(".txt>");
            initial.append(line);
            initial.append(".dat");
            cout<<initial<<endl;
            const  char* buffer;
            buffer = initial.c_str();
            system(buffer);
        }
    }
}
else
{
    cout<<"Unable to open file. \n";
}

VideoNames.close();

return 0;
}

Clearly something's going wrong. But without seeing your code, how could we know what? — Dennis, Oct 12 '11 at 11:22
Without more relevant details (a minimal working example that demonstrates your problem would be ideal, i.e. something short but complete that we can compile and run) it's impossible to do more than make wild guesses as to the problem here. — Flexo, Oct 12 '11 at 11:25
What makes you think the file is there? Does `ls` show it there? Are you in the correct directory? How are you opening it outside the terminal? — Wooble, Oct 12 '11 at 11:39
Try doing a `cout << buffer << endl;` prior to the call to `system()` to see what command you are *really* generating. — Paul R, Oct 12 '11 at 11:47

score 1 · Accepted Answer · answered Oct 12 '11 at 11:40

You are using strcat in a wrong way. I don't know if that's the cause of your problem, but it can result in undefined behavour;

int main(int argc,char* argv[])
{
    fstream RawStipFile;
    RawStipFile.open(strcat(argv[1],".txt"));

Here you modify argv[1]. You append 4 characters to it, without allocating any memory.

string line;
...
char* b;
b = &line[1];
VideoList<<b<<endl;
OutVideoStip.open(strcat(b, ".txt"));

a string takes care of it's own memory management. You can't asume it has reserved 4 more bytes for you to append. If you need to append, use string member functions, not strcat.

score 0 · Answer 2 · answered Oct 12 '11 at 11:43

0

just a loose guess: the current working directory is not the same?

Try either using chdir first or opening by absolute path /home/simon/VideoList.txt

answered Oct 12 '11 at 11:43

sehe

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Ubuntu - issue with opening a .txt file from terminal

2 Answers2