Compilare: user.c: In function ‘main’: user.c:81:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("ciclueuler.in", "r", stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:82:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("ciclueuler.out", "w", stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:117:13: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result] write(STDOUT_FILENO, obuf + oblen + 1, (CHUNK >> 2) - oblen - 2); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:127:5: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result] write(STDOUT_FILENO, obuf + oblen + 1, (CHUNK >> 2) - oblen - 2); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~