This is a simple C program that I used for calling the copy system call.
Usage: ./nfscopy /nfs/original.txt /nfs/copy.txt
---
nfscopy.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)
create mode 100644 nfscopy.c
diff --git a/nfscopy.c b/nfscopy.c
new file mode 100644
index 0000000..3417a14
--- /dev/null
+++ b/nfscopy.c
@@ -0,0 +1,59 @@
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+loff_t copy_file_range(int fd_in, loff_t *off_in, int fd_out,
+ loff_t *off_out, size_t len, unsigned int flags)
+{
+ return syscall(__NR_copy_file_range, fd_in, off_in, fd_out,
+ off_out, len, flags);
+}
+
+int main(int argc, char **argv)
+{
+ int fd_in, fd_out;
+ struct stat stat;
+ loff_t len, ret;
+ char buf[2];
+
+ if (argc != 3) {
+ fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
+ exit(EXIT_FAILURE);
+ }
+
+ fd_in = open(argv[1], O_RDONLY);
+ if (fd_in == -1) {
+ perror("open (argv[1])");
+ exit(EXIT_FAILURE);
+ }
+
+ if (fstat(fd_in, &stat) == -1) {
+ perror("fstat");
+ exit(EXIT_FAILURE);
+ }
+ len = stat.st_size;
+
+ fd_out = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC, 0644);
+ if (fd_out == -1) {
+ perror("open (argv[2])");
+ exit(EXIT_FAILURE);
+ }
+
+ do {
+ ret = copy_file_range(fd_in, NULL, fd_out, NULL, len, 0);
+ if (ret == -1) {
+ perror("copy_file_range");
+ exit(EXIT_FAILURE);
+ }
+
+ len -= ret;
+ } while (len > 0);
+
+ close(fd_in);
+ close(fd_out);
+ exit(EXIT_SUCCESS);
+}
--
2.7.2
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