Date: Fri, 08 Aug 2008 16:30:49 -0400 From: Chuck Robey <chuckr@telenix.org> To: "Carlos A. M. dos Santos" <unixmania@gmail.com> Cc: Pieter de Goeje <pieter@degoeje.nl>, freebsd-standards@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: read with timeout ?? Message-ID: <489CACF9.3030309@telenix.org> In-Reply-To: <e71790db0808080733p132180e9wba33d5840e1b954f@mail.gmail.com> References: <489B9D4D.4010009@telenix.org> <Pine.GSO.4.64.0808071813530.11980@zeno.ucsd.edu> <e71790db0808071950j32e196e4o42fab1aeb62ab8a4@mail.gmail.com> <200808081009.56521.pieter@degoeje.nl> <e71790db0808080733p132180e9wba33d5840e1b954f@mail.gmail.com>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Carlos A. M. dos Santos wrote: > On Fri, Aug 8, 2008 at 5:09 AM, Pieter de Goeje <pieter@degoeje.nl> wrote: >> On Friday 08 August 2008, Carlos A. M. dos Santos wrote: >>> On Thu, Aug 7, 2008 at 10:14 PM, Nate Eldredge <neldredge@math.ucsd.edu> >> wrote: >>>> On Thu, 7 Aug 2008, Chuck Robey wrote: >>>>> -----BEGIN PGP SIGNED MESSAGE----- >>>>> Hash: SHA1 >>>>> >>>>> I have my head lost in a code problem. I just hit a point where I need >>>>> to do a >>>>> read from an fd, but I need to associate it with a timeout, on the order >>>>> of 1 >>>>> second, something like that. I had the feeling that there's a function >>>>> in FreeBSD's libc that makes that simple, but I forget the function >>>>> name. If anyone can remember something like what I'm talking about, I >>>>> sure would appreciate a function name. I can figure out how it works, >>>>> if I could only >>>>> dredge up that name. >>>> man 2 select >>> If the fd is a socket then you can also use setsockopt(2) to set >>> SO_RCVTIMEO and check for EWOULDBLOCK (same as EAGAIN) upon read(2) or >>> recv(2) errors. The net effect is the same of using select but the >>> syntax is simpler, IMO. >> I think poll(2) is also simpler than select for this purpose. > > BTW, the setsockopt(2) manual page stands that a send or receive > timeout returns with the error EWOULDBLOCK but read(2) recv(2) send(2) > and write(2) only list EAGAIN in their ERRORS section. This is > harmless on BSD and Linux because EAGAIN and EWOULDBLOCK are the same, > but may sound confusing for people porting from/to System V. On HP-UX, > for instance, recv(2) lists both EAGAIN and EWOULDBLOCK. > > The setsockopt man page should be improved in order to explain > standards conformance and porting issues. I volunteer to do it but the > changes must be reviewed by a native English speaker. > Carlos, lets not go off on the socket trip for me... while I personally enjoy such a email, I have to admit my own needs fall more into a plain-jame serial line, nothing a socket-oriented thing could help me with. However, if you want to discuss this just fo the fun of it, oh please, by all means do carry on! -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkicrPkACgkQz62J6PPcoOmJowCfWPt1jHY4Gx0kOAQedVATHYDd BGYAoJe6JYuskZZe85AA63sgRBG1VGF0 =dNTn -----END PGP SIGNATURE-----
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