Re: Poor kernel handling of invalid select() timeout

Cameron Simpson (
7 Dec 1998 00:19:35 -0000

On 6 Dec 1998, in message <> (Dan Egnor) wrote:
| struct timeval tv;
| tv.tv_sec = 0;
| tv.tv_usec = -100000;
| printf("select => %d\n",select(0,NULL,NULL,NULL,&tv));
| This is trivially fixed, but I'm not sure what the correct behavior is with
| a negative timeout value. Presumably one of the following should happen:
| 1. select() fails with EINVAL
| 2. select() succeeds, returning immediately (as with a 0 timeout)
| The Linux select() man page says nothing about this case, but only documents
| EINVAL for a negative FD count. The Unix98 spec documents EINVAL in case of
| "invalid timeout value" but doesn't specify what that means. The wording for
| timeout behavior could be interpreted as allowing negative timeouts (they
| would just expire immediately).

Surely if tv_usec <0 || tv_usec >= 1000000 then EINVAL should issue?
(And, frankly, if tv_sec < 0.) Surely anything else is simply insane?

Cameron Simpson, DoD#743

Lady, have you ever seen a cat skeleton in a tree? - Kevin Dunn

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