logtee.c

   1 #define _GNU_SOURCE
   2 #include <fcntl.h>
   3 #include <poll.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <unistd.h>
   7 #include <errno.h>
   8 #include <limits.h>
   9
  10 #define BUFLEN 4096
  11
  12 int main(int argc, char *argv[])
  13 {
  14         int fd;
  15         int len, slen;
  16         int ret;
  17         int timeout;
  18         char *timeout_env;
  19         struct pollfd fds[] = { {
  20                         .fd = STDIN_FILENO,
  21                         .events = POLLIN | POLLERR,
  22                 }
  23         };
  24
  25         timeout_env = getenv("LOGTEE_TIMEOUT_MS");
  26         if (timeout_env)
  27                 timeout = atoi(timeout_env);
  28         else
  29                 timeout = -1;
  30
  31         if (argc != 2) {
  32                 fprintf(stderr, "Usage: %s <file>\n", argv[0]);
  33                 exit(EXIT_FAILURE);
  34         }
  35
  36         fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, 0644);
  37         if (fd == -1) {
  38                 perror("open");
  39                 exit(EXIT_FAILURE);
  40         }
  41
  42         fprintf(stderr, "Logging to %s: ", argv[1]);
  43
  44         slen = 0;
  45
  46         do {
  47                 ret = poll(fds, sizeof(fds) / sizeof(fds[0]), timeout);
  48                 if (ret == 0) {
  49                         fprintf(stderr, "Timed out after %d milliseconds of no output.\n", timeout);
  50                         exit(EXIT_FAILURE);
  51                 }
  52                 len = splice(STDIN_FILENO, NULL, fd, NULL, BUFLEN, SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
  53
  54                 if (len < 0) {
  55                         if (errno == EAGAIN)
  56                                 continue;
  57                         perror("tee");
  58                         exit(EXIT_FAILURE);
  59                 } else if (len == 0)
  60                         break;
  61                 slen += len;
  62                 if ((slen / BUFLEN) > 0) {
  63                         fprintf(stderr, ".");
  64                 }
  65                 slen = slen % BUFLEN;
  66
  67         } while (1);
  68         close(fd);
  69         fprintf(stderr, "\n");
  70         exit(EXIT_SUCCESS);
  71 }