ktee.c

   1 /*
   2  * A tee implementation using sys_tee. Stores stdin input in the given file
   3  * and duplicates that to stdout.
   4  */
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <string.h>
   9 #include <fcntl.h>
  10 #include <string.h>
  11 #include <sys/types.h>
  12 #include <errno.h>
  13 #include <assert.h>
  14 #include <limits.h>
  15
  16 #include "splice.h"
  17
  18 static int do_splice(int infd, int outfd, unsigned int len, char *msg)
  19 {
  20         while (len) {
  21                 int written = splice(infd, NULL, outfd, NULL, len, 0);
  22
  23                 if (written <= 0)
  24                         return error(msg);
  25
  26                 len -= written;
  27         }
  28
  29         return 0;
  30 }
  31
  32 static int usage(char *name)
  33 {
  34         fprintf(stderr, "... | %s: outfile\n", name);
  35         return 1;
  36 }
  37
  38 int main(int argc, char *argv[])
  39 {
  40         int fd;
  41
  42         if (argc < 2)
  43                 return usage(argv[0]);
  44
  45         if (check_input_pipe())
  46                 return usage(argv[0]);
  47
  48         fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
  49         if (fd < 0)
  50                 return error("open output");
  51
  52         do {
  53                 int tee_len = tee(STDIN_FILENO, STDOUT_FILENO, INT_MAX, SPLICE_F_NONBLOCK);
  54
  55                 if (tee_len < 0) {
  56                         if (errno == EAGAIN) {
  57                                 usleep(1000);
  58                                 continue;
  59                         }
  60                         return error("tee");
  61                 } else if (!tee_len)
  62                         break;
  63
  64                 /*
  65                  * Send output to file, also consumes input pipe.
  66                  */
  67                 if (do_splice(STDIN_FILENO, fd, tee_len, "splice-file"))
  68                         break;
  69         } while (1);
  70
  71         return 0;
  72 }