OT: bash vs. ksh subprocess counts

I realize this is way off topic (probably should be titled "WOT:...") for 
Oracle but #1, I don't currently belong to any good linux/redhat forums and #2, 
the issue found was from an Oracle maint. script :-)
Anyway, I'm on a RHEL 4.6 server (2.6.9-67.0.22.ELlargesmp) and noticed a given 
DBA maint script wasn't running.  It turns out that the only difference between 
when it last ran and now is someone changed the shell to be "bash" -> 
#!/bin/bash vs. #!/bin/ksh.  The script has a little if-test to start with, 
used as a way to determine if a previous iteration of the job is still running:

if [ `ps -ef|grep -cw $0` -gt 3 ]; then
   echo "$0 is already running"
   exit 2
fi

The problem is that when this "ps ..." command stream is run within an if-test, 
it returns a value 1 higher than under "ksh".  So when run out of cron it 
returns 4 under "bash" and 3 under "ksh".  I added "set -x" right before this 
command and here are the results:

                (under ksh)
+ grep -cw /home/test.sh
+ [ 3 -gt 3 ]

(under bash)
++ ps -ef
++ grep -cw /home/test.sh
+ '[' 4 -gt 3 ']'

This change only happens when running that command stream as part of an 
if-test.  So "ps -ef|grep -cw $0" returns "3" but "if [ `ps -ef|grep -cw $0` 
-gt 3 ]" evaluates to "4".  Am I interpreting this correctly in saying that 
bash forks another process when evaluating a command as part of an if-test 
while ksh does not?  Is there a more general way of explaining this difference 
is shell processing?

DAVID HERRING
DBA
Acxiom Corporation
EML   dave.herring@xxxxxxxxxx
TEL    630.944.4762
MBL   630.430.5988
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