ps weirdness...

cygwin@kosowsky.org cygwin@kosowsky.org
Tue Oct 22 00:39:00 GMT 2013


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

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.


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

This makes no sense, since I rebooted the machine less than 24 hours
ago (and the date is correct). Again the PID jumps around wildly
though here (as opposed to the bash case), the stime remains stuck on
Dec 31, whereas in the 'grep bash' case the stime seems to correspond
to the time the 'ps' command is run.

Interestingly, in the 'grep ssh-agent' case, 'ps -W | grep ssh-agent', never seems to generate a spurious 2nd process (despite dozens of trials).

Note that grepping for mintty, gives the same behavior as for 'ssh-agent' -- including the spurious Dec 31 date.

So, what is going on here with ps (inconsistently) generating "phanton" processes?

Note: I am running the latest 17.25 x86-64 under Win7 on an Intel i5.

Jeff

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