Simple C/P question in C++

This is a discussion on Simple C/P question in C++ within the C++ Programming forums, part of the General Programming Boards category; What code could I use to copy a file to another location on the computer? Thanks in advance, Will...

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    Simple C/P question in C++

    What code could I use to copy a file to another location on the computer?

    Thanks in advance,
    Will

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    Depends on what you want to achieve and on what OS, but the standard C way is to use two calls to fopen() to open the existing and create the new location file, and then fread()/fwrite() in a loop for as much as you need to, then fclose().

    On specific systems, such as Windows, there are system functions to do this for you, but it locks you in with that OS.

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    Last edited by matsp; 02-09-2008 at 01:28 PM.
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    Thanks. That's all I need to know. If you wanted to know, I have windows xp pro. And I was just asking the question for future knowledge.

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    C++まいる!Cをこわせ! Elysia's Avatar
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    For Windows API, CopyFile and CopyFileEx works. There's also MoveFile and MoveFileEx.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Thanks Elysia, at my stage, every piece of info counts.

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    Depends on what you want to achieve and on what OS, but the standard C way is to use two calls to fopen() to open the existing and create the new location file, and then fread()/fwrite() in a loop for as much as you need to, then fclose().
    In C++, of course, one would use file streams. Perhaps ifstream, ofstream, and the >> and << operators. Maybe something like this (untested!):
    Code:
    #include <fstream>
    
    bool copy_file(const char *from, const char *to) {
        std::ifstream in(from);
        if(!in.is_open()) return false;
    
        std::ofstream out(to);
        if(!out.is_open()) return false;
    
        char c;
        while(in >> c) out << c;
    
        return true;
    }
    There's also MoveFile and MoveFileEx.
    There's also the standard C function rename() for that . . . .
    dwk

    Seek and ye shall find. quaere et invenies.

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    C++まいる!Cをこわせ! Elysia's Avatar
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    Are you kidding? That solution is horrible
    Reading and writing a char at a time will take forever.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Quote Originally Posted by Elysia View Post
    Are you kidding? That solution is horrible
    Reading and writing a char at a time will take forever.
    Thanks Elysia, you're a programming master! How the hell do you know everything?

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    If you're using the fstream classes you'd want to open the files in binary mode though, unless you know they're text files...
    Of course the easiest and least portable way to do it is using the system() function.

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    Thanks, all. And I'll keep this forum in my bookmarks! It's people are full of information.

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    The easiest way is this:

    Code:
    copy_to << copy_from.rdbuf();
    Where copy_from and copy_to are ifstream and ofstream, properly declared and opened. Using OS specific functions will be more optimal, however.
    It is too clear and so it is hard to see.
    A dunce once searched for fire with a lighted lantern.
    Had he known what fire was,
    He could have cooked his rice much sooner.

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    Quote Originally Posted by PЯO View Post
    Thanks Elysia, you're a programming master! How the hell do you know everything?
    I don't believe Elysia knows everything, but it's pretty obvious that the overhead of checking and reading every single character of the input file and writing each one individually to the output file will be slower than doing it with blocks. fstream supports a read & write function [respectively for ifstream and ofstream, commonly for fstream]. Reading blocks of 4KB or so will be reasonably efficient (even multiples of 2 to the power of n is also a good idea, as disk blocks are always even powers of 2). Bigger blocks may work better in some OS's & HW combos, but not at all guaranteed [and the benefit gets smaller and smaller as the blocks grow bigger, until you start loosing out again for really big blocks].

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    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by matsp View Post
    I don't believe Elysia knows everything...
    Hehehe well, from a newbie's perspective, we are all "gods" who know everything.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  14. #14
    Frequently Quite Prolix dwks's Avatar
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    Sorry for the inefficient program . . . my C++ skills are such that I didn't feel confident enough to post a solution that used blocks instead of characters . . . now ask for a C version, and you might get something.

    Hehehe well, from a newbie's perspective, we are all "gods" who know everything.
    I guess everyone is a newbie compared to Salem, then.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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