copying a file in c linux

Linux_Kid_ · 09-07-2009, 06:05 AM

Hi All,

I searched on google but could not find out any Linux API for copying file .Rename is for moving a file from a location to other,Is there any API for copy too.

or i have to copy byte by byte to a new file.

System(cp / /tmp) call is another alternative.Bt as i studied its not a good practice to use system call in C program..

Please help..

Thanks and Regards

Wim Sturkenboom · 09-07-2009, 10:22 AM

You can determine the filesize, allocate a buffer for that size and read the file into the buffer. Next write the buffer to a new file.

As far as I know, there is indeed no copy function.

tuxdev · 09-07-2009, 10:51 AM

Copy in 1M chunks using a statically allocated buffer. This prevents nasty swapping or running out of memory for large files.

ta0kira · 09-07-2009, 11:02 AM

I sometimes copy a file using mmap to avoid allocating a buffer. I don't know if this is actually faster, though.
Kevin Barry

Hko · 09-07-2009, 05:32 PM

I always think the most efficient way is to use the read(2) and write(2) syscalls and call stat(2) on the destination directory first to find the optimal buffer size.

From "man 2 stat":

Quote:

The st_blksize field gives the "preferred" blocksize for efficient file system I/O. (Writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.)

But when copying many small files to the same directory, it may become sub-optimal to call stat() for every file...