Copying files in c program

CelticBlues · 08-11-2008, 11:41 AM

Is there a way to copy a file at run time in a c or c++ app in linux? I am assuming there is something where can execute a system level call such as 'cp' and pass it parameters, but I haven't found anything like that. I found exec, but only in reference to shell scripts.

thanks,
CB

TB0ne · 08-11-2008, 12:36 PM

Quote:

Originally Posted by CelticBlues

Is there a way to copy a file at run time in a c or c++ app in linux? I am assuming there is something where can execute a system level call such as 'cp' and pass it parameters, but I haven't found anything like that. I found exec, but only in reference to shell scripts.

thanks,
CB

This link may help you:

http://cboard.cprogramming.com/showthread.php?p=744616

This link:

http://www.elook.org/programming/c/system.html

Covers how to call system-commands from a C program. Very basic C programming, surprised it's not in your books.

Mr. C. · 08-11-2008, 12:46 PM

Or if you need a quick solution, you can use system()

man 3 system

CelticBlues · 08-11-2008, 01:01 PM

I tried system, and it returned 0, which is what it should return if the command executed without error I think...

I tried this:

system("cp file1.ext file2.ext");

Is that right?

CB

Quote:

Originally Posted by Mr. C.

Or if you need a quick solution, you can use system()

man 3 system

Mr. C. · 08-11-2008, 01:27 PM

That is correct.

ta0kira · 08-11-2008, 06:18 PM

Without system:

Code:

#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>


#define BUFFER_SIZE 256

int main(int argc, char *argv[])
{
	//check number of arguments

	if (argc != 3)
	{
	fprintf(stderr, "%s [input file] [output file]\n", argv[0]);
	return 1;
	}


	//open the first file "read-only"

	int input = open(argv[1], O_RDONLY);
	if (input < 0)
	{
	fprintf(stderr, "%s: could not read file '%s'\n", argv[0], argv[1]);
	return 1;
	}


	//find the permissions of the first file so we can copy them

	int permissions = 0644;
	struct stat file_stats;

	if (fstat(input, &file_stats) != -1)
	permissions = file_stats.st_mode & 07777;


	//open the second file "write-only" using the first file's permissions
	//note: the permissions will only be used if the file doesn't exist

	int output = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, permissions);
	if (output < 0)
	{
	fprintf(stderr, "%s: could not write file '%s'\n", argv[0], argv[2]);
	return 1;
	}


	//create a modestly-sized buffer for holding data

	char buffer[BUFFER_SIZE];
	ssize_t read_size = 0;


	//read as much data as the first file contains

	while ((read_size = read(input, buffer, BUFFER_SIZE)) != 0)
	{
	if (read_size == (ssize_t) -1)
	 {
	fprintf(stderr, "%s: error reading file '%s'\n", argv[0], argv[1]);
	return 1;
	 }

	else if (write(output, buffer, read_size) != read_size)
	 {
	fprintf(stderr, "%s: error writing file '%s'\n", argv[0], argv[2]);
	return 1;
	 }
	}


	return 0;
}

ta0kira