Date: Fri, 3 Mar 2017 14:42:40 -0800 From: "Ngie Cooper (yaneurabeya)" <yaneurabeya@gmail.com> To: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> Cc: Dirk-Willem van Gulik <dirkx@webweaving.org>, freebsd-hackers@freebsd.org Subject: Re: kill -0 <pid> --- side effect or supported Message-ID: <35C6F2AA-309E-4D58-8191-AB99F0195BEC@gmail.com> In-Reply-To: <201703032230.v23MUg5b072955@pdx.rh.CN85.dnsmgr.net> References: <201703032230.v23MUg5b072955@pdx.rh.CN85.dnsmgr.net>
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--Apple-Mail=_1FCA6944-FF7B-4140-99D2-CE5A1AACB067 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On Mar 3, 2017, at 14:30, Rodney W. Grimes = <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> wrote: >=20 > -- Start of PGP signed section. > [ Charset UTF-8 unsupported, converting... ] >>=20 >>> On Mar 3, 2017, at 14:12, Dirk-Willem van Gulik = <dirkx@webweaving.org> wrote: >>>=20 >>> I regularly use 'kill -0 <pid>' on FreeBSD as a way to test if a = certain process is still running (but without actually sending the = signal). And I think it has worked reliably since the mid 80's. >>>=20 >>> Is it actually a properly supported use - as I recently happened to = notice that it does not seem to be all that documented in kill( >>=20 >> It better work. I have code that relies on it :)? >>=20 >> It does work as you noted, according to truss: >>=20 >> # sudo truss -ff kill -0 1 2>&1 >> ... >> 79940: kill(1,0) =3D 0 (0x0) >> ? >> # >>=20 >> As noted in kill(2), this is one of the valid values: >>=20 >> a group of processes. The sig argument may be one of the signals >> specified in sigaction(2) or it may be 0, in which case error = checking is > ^^^^^^^^^^^^^^^^ >=20 > That bit of information should be promoted from kill(2) to kill(1) by > adding 0 to the list as ?. Actually=E2=80=A6 it is mentioned in kill(1) =E2=80=94 you just have to = read between the lines: -signal_number A non-negative decimal integer, specifying the signal to be = sent instead of the default TERM. 0 is technically a non-negative real number. It might be a good idea to clarify this point/behavior by pointing to = kill(2) for the signal behavior/description noted above. Thanks, -Ngie --Apple-Mail=_1FCA6944-FF7B-4140-99D2-CE5A1AACB067 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJYufFgAAoJEPWDqSZpMIYVfL0QAMIt8yKXvrChGbPR/LeWkPhf n4p8+JLgcFyoDNIpr/LEUHAdCK8NWxAwY+ZmHaP95zs5txGpde1hU4QUnXsxoNu7 c8z57PESnczQBViHQhCgL7XDVodV7GWdL4Xm/0mNgFE5BsDYia0+0XbLl0Kj93yI /drwWGvEygnwYa6uZpDugJaP546Ng/d4izYY3HnvVWMRsi4WphNZs7SYfbPOMUdP an7CxvcXe/YGKd0sZVHq7Pkej1W/nWEFZJHCQ+AbrriwaHkCNpCBYJrYdsYCtrce P9ssIEj75f2tpn1O/Ybf5f8HwcBDFxG/zXnxI+/M5ZH1XlVSmSM3hO3gPNK9/PAO xjLMmOrrVlxCbKxnDiIiWhPQBSNpwzYgWUi6zDqrIOdhKc7z8NCykQUqrdfwQozm dLgtq9y1vTmSPeIYcdR1J1MD3y71l0/BaqJeBpNwgJa6fu3H2RUAwnlF0LGY2J0A FAErVi6allBejHKx+MEXBzerFO9PI8GLH/st8fX1BlrSRqsSe0BHz6x38TO8RXUK utnyFEKCLkzwUMp1Nfng+jAZheNKSoSPisX5TLPUsE7lDypmaVbY8inlVGH3/Q76 qOK2HJMhO3RXGBQhDiQUitbYkl4azuUCkObICTVR6b/OtrFtGnrSExS7dNErvv2S 0KCuaAuIM6H1etOW880J =YB3I -----END PGP SIGNATURE----- --Apple-Mail=_1FCA6944-FF7B-4140-99D2-CE5A1AACB067--
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