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Date: Wed, 23 Oct 2013 08:55:40 -0400
To: cygwin AT cygwin DOT com
Subject: Re: ps weirdness...
In-reply-to: <20131023082535.GA5134@calimero.vinschen.de>
References: <21093 DOT 42532 DOT 550364 DOT 992074 AT consult DOT pretender>	<20131023082535 DOT GA5134 AT calimero DOT vinschen DOT de>
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Corinna Vinschen wrote at about 10:25:35 +0200 on Wednesday, October 23, 2013:
 > On Oct 21 18:09, cygwin wrote:
 > > When I type 'ps', I get as expected the following processes:
 > > 
 > >       PID    PPID    PGID     WINPID   TTY     UID    STIME COMMAND
 > >     18036    3188   18036      17792  pty0    1001 16:54:33 /usr/bin/ps
 > >      3188    1688    3188       3212  pty0    1001 06:59:16 /usr/bin/bash
 > >      1688       1    1688       1688  ?       1001 06:59:15 /usr/bin/mintty
 > >      2392       1    2392       2392  ?       1001 11:00:03 /usr/bin/ssh-agent
 > > 
 > > When I type 'ps | grep bash', about 2/3 of the time, I get:
 > >  	 3188    1688    3188       3212  pty0    1001 06:59:16 /usr/bin/bash
 > > 
 > > HOWEVER, about 1/3 of the time, I get:
 > >   16832    3188   17792      16832  pty0    1001 16:56:44 /usr/bin/bash
 > >   3188    1688    3188       3212  pty0    1001 06:59:16 /usr/bin/bash
 > 
 > When you pipe ps to grep, the shell forks and execs two processes, ps
 > and grep.  What you see is one of the forked bash processes.  They are
 > shortlived, but depending on the order of execution they may still
 > linger in the process list when ps creates the process list.
 > 
 > > And there is no bash process launched in the interim. Moreover, this
 > > second PID jumps around (both up and down) wildly rather than being
 > > constant or even relatively sequential.
 > 
 > PIDs under Windows are not sequential.
 > 
 > > In such cases, ps -W, similarly generates 2 bash processes:
 > > 
 > >      3188    1688    3188       3212  pty0    1001 06:59:16 /usr/bin/bash
 > >     16460       0       0      16460  pty0    1001 17:44:29 C:\cygwin\bin\bash.exe
 > > 
 > > Even more interesting, when I type 'ps | grep ssh-agent', about 2/3 of the time, I get:
 > >   2392       1    2392       2392  ?       1001 11:00:03 /usr/bin/ssh-agent
 > > 
 > > HOWEVER, about 1/3 of the time, I get:
 > >   2392       1    2392       2392  ?       1001 11:00:03 /usr/bin/ssh-agent
 > >   19176       0       0      19176  pty0    1001   Dec 31 /usr/bin/ssh-agent
 > 
 > Hmm, I can't reproduce this one.  I tried a hundreds of times, but
 > there was not a single instance of bash shown as a Windows process.

The Windows case seemed to be less reproducible... but it did
happen. Given your explanation as a short-lived forked process, I
imagine it would depend to a degree on the speed and architectures
(e.g., #cores) of the CPU.

HOWEVER, I still don't understand the 'dec 31' date for a short-lived
process...

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