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
  13 main(int argc, char *argv[])
  14 {
  15         int fd;
  16         int len, slen;
  17         int ret;
  18         int timeout;
  19         char *timeout_env;
  20         struct pollfd fds[] = {{
  21                 .fd = STDIN_FILENO,
  22                 .events = POLLIN | POLLERR,
  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,
  53                              BUFLEN, SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
  54
  55                 if (len < 0) {
  56                         if (errno == EAGAIN)
  57                                 continue;
  58                         perror("tee");
  59                         exit(EXIT_FAILURE);
  60                 } else
  61                         if (len == 0)
  62                                 break;
  63                 slen += len;
  64                 if ((slen/BUFLEN) > 0) {
  65                         fprintf(stderr, ".");
  66                 }
  67                 slen = slen % BUFLEN;
  68
  69         } while (1);
  70         close(fd);
  71         fprintf(stderr, "\n");
  72         exit(EXIT_SUCCESS);
  73 }