man/journal-iterate-wait.c

   1 /* SPDX-License-Identifier: MIT-0 */
   2
   3 #include <errno.h>
   4 #include <stdio.h>
   5 #include <systemd/sd-journal.h>
   6
   7 int main(int argc, char *argv[]) {
   8   int r;
   9   sd_journal *j;
  10   r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
  11   if (r < 0) {
  12     errno = -r;
  13     fprintf(stderr, "Failed to open journal: %m\n");
  14     return 1;
  15   }
  16   for (;;)  {
  17     const void *d;
  18     size_t l;
  19     r = sd_journal_next(j);
  20     if (r < 0) {
  21       errno = -r;
  22       fprintf(stderr, "Failed to iterate to next entry: %m\n");
  23       break;
  24     }
  25     if (r == 0) {
  26       /* Reached the end, let's wait for changes, and try again */
  27       r = sd_journal_wait(j, (uint64_t) -1);
  28       if (r < 0) {
  29         errno = -r;
  30         fprintf(stderr, "Failed to wait for changes: %m\n");
  31         break;
  32       }
  33       continue;
  34     }
  35     r = sd_journal_get_data(j, "MESSAGE", &d, &l);
  36     if (r < 0) {
  37       errno = -r;
  38       fprintf(stderr, "Failed to read message field: %m\n");
  39       continue;
  40     }
  41     printf("%.*s\n", (int) l, (const char*) d);
  42   }
  43   sd_journal_close(j);
  44   return 0;
  45 }