Path: utzoo!utgpu!watmath!clyde!bellcore!rutgers!mailrus!ncar!ames!haven!mimsy!jds From: jds@mimsy.UUCP (James da Silva) Newsgroups: comp.unix.questions Subject: Re: tail -f Summary: sleep(1) Keywords: how does it work Message-ID: <14888@mimsy.UUCP> Date: 7 Dec 88 16:33:34 GMT References: <412@fedeva.UUCP> Reply-To: jds@mimsy.umd.edu (James da Silva) Organization: University of Maryland, Department of Computer Science Lines: 21 In article <412@fedeva.UUCP> jbr0871@fedeva.UUCP (Blaine Robertson) writes: >Can someone please tell me how 'tail -f' works?. Obviously, it does not >do a busy loop while doing a stat on the file. I know that it has got >to be blocked, waiting for the length to change, but how does it get >notified of a change? Thanks in advance for any responses. Actually, tail doesn't get notified of a change. It simply sleeps for a second, then tries a read(). Probably something like this: while(1) { sleep(1); while(size=read(file,buffer,BSIZE)) write(1,buffer,size); } Nothing fancy, I'm afraid. Jaime ........................................................................... : domain: jds@mimsy.umd.edu James da Silva : path: uunet!mimsy!jds