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Re: ctrl-c doesn't reliably kill ping
- From: Warren Young <wyml at etr-usa dot com>
- To: The Cygwin Mailing List <cygwin at cygwin dot com>
- Date: Wed, 16 Mar 2016 10:50:47 -0600
- Subject: Re: ctrl-c doesn't reliably kill ping
- Authentication-results: sourceware.org; auth=none
- References: <56E6F25A dot 7070000 at gmx dot de> <56E75B3E dot 7020102 at farance dot com> <CAD8GWstL-rUm9=q8tpReiiHm8Tmm94Caq7jQyszZ02Tw=EN_TQ at mail dot gmail dot com>
On Mar 16, 2016, at 10:07 AM, Lee <ler762@gmail.com> wrote:
>
> The last time I tried the cygwin ping program it didn't return a
> failure status
It does if you donât Ctrl-C out of it. So, if youâre using it from a script, you just ask for one packet:
# ping does.not.exist 1 1
ping: unknown host does.not.exist
# echo $?
1
Note my fine new # prompt, indicating an admin shell, which has been required for Cygwin ping from the very beginning[1] due to the restrictions on raw sockets added in Windows XP SP2. Windows ping gets around this by special dispensation of the kernel.[2]
If you want to say Cygwin ping is âuselessâ because of that, blame Microsoft for not allowing ICMP raw sockets for normal users [3] or for not reinventing suid bits correctly. (UAC = not correct.)
Older Linuxes and some modern Unixes set the suid bit on the ping program to get around this, and newer Linuxes use getcap/setcap to give the ping program the right to use raw sockets so they donât need u+s.[4]
[1] https://cygwin.com/ml/cygwin-apps/2005-01/msg00124.html
[2] It loads IPHLPAPI.DLL at run time in order to call IcmpSendEcho()
[3] https://goo.gl/o25d6U
[4] http://linux.die.net/man/8/setcap
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