"ps output line ... is shorter than its associated header"

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System:

   RHEL 7.6

   cfengine-community 3.10.3


CFEngine log files and emails for a small number of our clients have:


     "ps output line '...' is shorter than its associated header"


Correspondingly the "-v" output from "cf-agent" has:


-----------

   verbose: C: BEGIN classes / conditions (pass 1)

   verbose: Observe process table with /bin/ps -eo 
user,pid,ppid,pgid,pcpu,pmem,vsz,ni,rss:9,nlwp,stime,etime,time,args

      error: ps output line 'user-id  35911      1   8597  0.0  0.0 123668   0  
    2504    2 Mar11  2-22:28:49 00:00:00' is shorter than its associated header
-----------

(I've obfuscated the user-id.)

Running that quoted 'ps' command manually and scanning the output, I see:

-----------
user-id  35772      1   8597  0.0  0.3 1022928  0     54292    5 Mar11  
2-22:32:59 00:00:48 kleopatra
user-id  35905      1   8597  0.0  0.0 782440   0      6144    5 Mar11  
2-22:32:04 00:00:28  /etc/speech-dispatcher/modules//espeak.conf
user-id  35911      1   8597  0.0  0.0 123668   0      2504    2 Mar11  
2-22:32:04 00:00:00
user-id  35913      1  35913  0.0  0.0  94272   0       952    2 Mar11  
2-22:32:04 00:00:00 /usr/bin/speech-dispatcher
-----------


Note that pid 35911 lacks any command-line information ("args").


(As an associated observation (clearer in a monospaced font) pid 35905 has two 
spaces, rather than a single space, separating the end of the time, 00:00:28, 
from the args, "/etc/speech...".  This is probably irrelevant.)


Our calling bundle is doing a 'processexists("...").


It would seem that when "cf-agent" is internally invoking a 'ps' command, the 
processing of the output is not cleanly allowing for an empty "args" result 
(our pid 35911).


This seems to be a bug.  (A quick Google search indicates that something 
similar has been seen a few years ago in AIX and Solaris: CFE-2446 and 
CFE-2161.)  But we are RHEL7.6  Any thoughts?


Of course, this prompts again the thought about whether all this could be much 
more cleanly handled on OSes that support "/proc", relegating the "ps" 
mechanism to those few OSes that lack "/proc": CFE-1655.  But that is probably 
another story for another time...


-- David Lee


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