Function cbm_tail_log

src/foundation/subprocess.c:94–136

Tail newly-appended complete lines from the child log, starting at *tail_pos. * A partial (non-newline-terminated) final line is left buffered: *tail_pos is * not advanced past it, so it is re-read once completed. Returns true if any * complete line was consumed (i.e. there was progress). */

 * not advanced past it, so it is re-read once completed. Returns true if any
 * complete line was consumed (i.e. there was progress). */
static bool cbm_tail_log(const char *log_file, long *tail_pos, cbm_proc_log_cb cb, void *ud) {
    if (!log_file) {
        return false;
    }
    FILE *lf = fopen(log_file, "r");
    if (!lf) {
        return false;
    }
    bool progressed = false;
    if (fseek(lf, *tail_pos, SEEK_SET) == 0) {
        char line[1024];
        for (;;) {
            long before = ftell(lf);
            if (!fgets(line, sizeof(line), lf)) {
                break;
            }
            size_t l = strlen(line);
            bool complete = (l > 0 && line[l - 1] == '\n');
            if (complete) {
                line[l - 1] = '\0';
                *tail_pos = ftell(lf);
                progressed = true;
                if (line[0] && cb) {
                    cb(line, ud);
                }
            } else if (l == sizeof(line) - 1) {
                /* Oversized line filled the buffer without a newline — consume it
                 * anyway (counts as progress) so we never stall on one long line. */
                *tail_pos = ftell(lf);
                progressed = true;
                if (cb) {
                    cb(line, ud);
                }
            } else {
                /* Genuine partial final line — keep it buffered for next poll. */
                *tail_pos = before;
                break;
            }
        }
    }
    fclose(lf);
    return progressed;
}

/* ── Windows command-line quoting (pure; unit-tested on every platform) ─────── */