C++ FileIO Copy -VS- System("cp file1.x file2.x)

Question

Would it be quicker/efficient to write a file copy routine or should I just execute a System call to cp?

(The file system could differ [nfs, local, reiser, etc], however

Answer 1

Invoking a shell by using system () function is not efficient and not very secure.

The most efficient way to copy a file in Linux is to use sendfile () system call. On Windows, CopyFile () API function or one of its related variants should be used.

Example using sendfile:

#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main (int argc, char* argv[])
{
 int read_fd;
 int write_fd;
 struct stat stat_buf;
 off_t offset = 0;

 /* Open the input file. */
 read_fd = open (argv[1], O_RDONLY);
 /* Stat the input file to obtain its size. */
 fstat (read_fd, &stat_buf);
 /* Open the output file for writing, with the same permissions as the
   source file. */
 write_fd = open (argv[2], O_WRONLY | O_CREAT, stat_buf.st_mode);
 /* Blast the bytes from one file to the other. */
 sendfile (write_fd, read_fd, &offset, stat_buf.st_size);
 /* Close up. */
 close (read_fd);
 close (write_fd);

 return 0;
}

If you do not want your code to be platform dependent, you may stick with more portable solutions - Boost File System library or std::fstream.

Example using Boost (more complete example):

copy_file (source_path, destination_path, copy_option::overwrite_if_exists);

Example using C++ std::fstream:

ifstream f1 ("input.txt", fstream::binary);
ofstream f2 ("output.txt", fstream::trunc|fstream::binary);
f2 << f1.rdbuf ();