From: pjfarley AT dorsai DOT org (Peter J. Farley III)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Problem with fstreams...
Date: Thu, 28 Aug 1997 01:55:52 GMT
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References: <5tps7b$rpo$1 AT news DOT sendit DOT nodak DOT edu> <5tq24a$b6$1 AT news DOT sendit DOT nodak DOT edu>
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adalee AT sendit DOT sendit DOT nodak DOT edu (Adam W Lee) wrote:

>Adam W Lee (adalee AT sendit DOT sendit DOT nodak DOT edu) wrote:
>: I'm trying to write a program to read a file and write it to another file
>: in C++, but my program quits like halfway through the file with a read
>: error or something to that effect...  Here's some pseudo-code.

Adam,

I took your example and tried it myself, and yes, it fails as you say.
After a little experimentation, I found a version that works perfectly
under DJGPP.  It seems that the "ios::in" and "ios::out" are
*required* in the open process, even though the files are declared
ifstream and ofstream, respectively.  Please try my version to
confirm.

#include <fstream.h>

int main(int argc, char *argv[])
{
    char temp[1025];
    if(argc<3)
    {
        cout << "Usage: " << argv[0] << " <infile> <outfile>" << endl;
        return 1;
    }
    ifstream in;
//  in.open(argv[1], ios::binary);            <=== THIS FAILS
    in.open(argv[1], ios::in | ios::binary);    // THIS WORKS
    if(in.fail())
    {
        cout << "Error opening " << argv[1] << endl;
        return 2;
    }
    ofstream out;
//  out.open(argv[2], ios::binary);           <=== THIS FAILS
    out.open(argv[2], ios::out | ios::binary);  // THIS WORKS
    if(out.fail())
    {
        cout << "Error opening " << argv[2] << endl;
        cout << "Error opening " << argv[2] << endl;
        return 3;
    }
    while (!in.eof()&&!in.fail()&&!out.fail())
    {
        in.read(temp,1024);
        cout << "Length read was " << in.gcount() << endl;
        cout << "in.eof=" << in.eof() << ", in.fail=" << in.fail() <<
            ", out.fail=" << out.fail() << endl;
        out.write(temp, in.gcount());
    }
    out.flush();
    if(in.eof())
        cout << "End of file reached." << endl;
    if(in.fail()&&!in.eof())
        cout << "Error reading " << argv[1] << "." << endl;
    if(out.fail())
        cout << "Error writing " << argv[2] << "." << endl;
    in.close();
    out.close();
    return 0;
}

----------------------------------------------------
Peter J. Farley III (pjfarley AT dorsai DOT org)