pipe.c: In function 'main': pipe.c:27: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result pipe.c:28: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result pipe.c:32: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result pipe.c:33: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result pipe.c:34: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result pipe.c:43: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result