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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/uio.h>
#include <sys/types.h>
#include <linux/fs.h> /* for RWF_HIPRI */
int main()
{
char tmp[] = "/tmp/tst-preadv2-XXXXXX";
int fd;
struct iovec iov[2];
char *str0 = "hello ";
char *str1 = "world\n";
char input[16];
int nio;
fd = mkstemp (tmp);
if (fd == -1) {
puts ("mkstemp failed");
return 1;
}
iov[0].iov_base = str0;
iov[0].iov_len = strlen(str0);
iov[1].iov_base = str1;
iov[1].iov_len = strlen(str1) + 1; /* null terminator */
nio = syscall(SYS_pwritev2, fd, iov, 2, 0, 0, RWF_DSYNC);
if (nio <= 0) {
puts ("failed to write to fd");
return 1;
}
/* Read in the second string into the first buffer */
iov[0].iov_base = input;
iov[0].iov_len = strlen(str1) + 1; /* null terminator */
nio = syscall(SYS_preadv2, fd, iov, 1, strlen(str0), 0, RWF_HIPRI);
if (nio <= 0) {
printf ("failed to read fd %d\n", nio);
return 1;
}
if (strncmp(iov[0].iov_base, iov[1].iov_base, strlen(str1)) == 0)
printf ("syscall(SYS_preadv2) read %s", (char *) iov[0].iov_base);
if (close(fd) != 0) {
puts ("failed to close read fd");
return 1;
}
if (unlink(tmp) != 0) {
puts ("failed to unlink file");
return 1;
}
return 0;
}
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