User space程序读取kernel log 并保存

#include <string.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <fcntl.h>

static void run_kmsg_dump_daemon(void)
{
 int pid;

 pid = fork();
 if (pid == 0) {
  int fd_1;
  int fd_2;
  int i;

  /* start */
  if (fork() != 0)
   exit(0);

  if (setsid() < 0)
   perror("setsid");

  if (fork() != 0)
   exit(0);

  chdir("/");
  umask(0);

  for (i = 0; i < 64; i++)
   close(i);
  /* done */

  fd_1 = open("/proc/kmsg", O_RDONLY);
  if (fd_1 < 0) {
   fprintf(stdout, "open error: %s\n", strerror(errno));
   goto out;
  }

  /*
   determine the name of new log file
  */
  for (i = 0; i < 1000; i++) {
   char log_file[1024] = { '\0' };

   (void) snprintf(log_file, sizeof(log_file) - 1, "%s_%d.log", "/data/kmsg", i);
   fd_2 = open(log_file, O_EXCL|O_CREAT|O_WRONLY, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
   if (fd_2 > 0)
    break;
  }

  while (1) {
   struct timeval time;
   fd_set rfd;
   int nready;

   FD_ZERO(&rfd);
   FD_SET(fd_1, &rfd);

   time.tv_sec = 1;
   time.tv_usec = 0;

   nready = select(FD_SETSIZE, &rfd, NULL, NULL, &time);
   if (nready > 0) {
    char buf[4096] = {'\0'};
    int n;

    n = read(fd_1, buf, sizeof(buf) - 1);
    if (n > 0)
     (void) write(fd_2, buf, n);
   } else if (nready < 0) {
    fprintf(stdout, "'select()' failed with error: %s\n", strerror(errno));
    break;
   }
  }

  out:
   exit(0)
 }

 /* let parent continue its job */
 return;
   }

int main()

{

    run_kmsg_dump_daemon();

}