Question

In cmd.exe, I can execute the command ‘copy c:\hello.txt c:\hello2.txt’ and it worked fine. But in my C program, I ran this piece of code and got the following error:

#include <iostream>  using namespace std;  int main() {     system('copy c:\hello.txt c:\hello2.txt');     system('pause');      return 0; } 

Output: The system cannot find the file specified.

Anybody know what is going on here?

Answer 1

Inside C strings (and quite a few other languages that use the same escaping rules), \ should be \\ since it’s the escape character. It allows you to enter, in normal text, non-printable characters such as:

• the tab character \t.
• the carriage-return character \r.
• the newline character \n.
• others which I won’t cover in detail.

Since \ is used as the escape character, we need a way to put an actual '\' into a string. This is done with the sequence \\.

Your line should therefore be:

system('copy c:\\hello.txt c:\\hello2.txt'); 

This can sometimes lead to obscure errors with commands like:

FILE *fh = fopen ('c:\text.dat', 'w'); 

where the \t is actually the tab character and the file that you’re trying to open is:

            c:TABext.dat.