logtee.c

   1 #define _GNU_SOURCE
   2 #include <fcntl.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <unistd.h>
   6 #include <errno.h>
   7 #include <limits.h>
   8
   9 #define BUFLEN 4096
  10
  11 int
  12 main(int argc, char *argv[])
  13 {
  14         int fd;
  15         int len, slen;
  16
  17         if (argc != 2) {
  18                 fprintf(stderr, "Usage: %s <file>\n", argv[0]);
  19                 exit(EXIT_FAILURE);
  20         }
  21
  22         fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
  23         if (fd == -1) {
  24                 perror("open");
  25                 exit(EXIT_FAILURE);
  26         }
  27
  28         fprintf(stderr, "Logging to %s: ", argv[1]);
  29
  30         slen = 0;
  31
  32         do {
  33                 len = splice(STDIN_FILENO, NULL, fd, NULL,
  34                              BUFLEN, SPLICE_F_MOVE);
  35
  36                 if (len < 0) {
  37                         if (errno == EAGAIN)
  38                                 continue;
  39                         perror("tee");
  40                         exit(EXIT_FAILURE);
  41                 } else
  42                         if (len == 0)
  43                                 break;
  44                 slen += len;
  45                 if ((slen/BUFLEN) > 0) {
  46                         fprintf(stderr, ".");
  47                 }
  48                 slen = slen % BUFLEN;
  49
  50         } while (1);
  51         close(fd);
  52         fprintf(stderr, "\n");
  53         exit(EXIT_SUCCESS);
  54 }