Exit Codes

I have TWO questions:

1. What does Non-zero exit code mean? (pls refer to the snippet below)
<snip>
procmail: [30253] Wed Oct  3 09:29:21 2001
procmail: Assigning "LOGABSTRACT=all"
procmail: Assigning "MAILDIR=/home/wash/Mail"
procmail: Assigning "SHELL=/bin/sh"
procmail: Executing " formail -xFrom: | fgrep -if $PMDIR/green.lst"
procmail: Non-zero exitcode (1) from " formail -xFrom: | fgrep -if 
$PMDIR/green.lst"
procmail: No match on " formail -xFrom: | fgrep -if $PMDIR/green.lst"
procmail: Assigning "INCLUDERC=/home/wash/.LOG//rc.message-size"
procmail: No match on "> 500000"
procmail: Executing "/home/wash/.LOG//RecPath"
procmail: No match on "^From.*wash"
procmail: Executing "fgrep,-i,/home/wash/.LOG//black.lst"
procmail: Non-zero exitcode (1) from "fgrep"
procmail: Assigning "LASTFOLDER=fgrep -i /home/wash/.LOG//black.lst"
procmail: No match on "fgrep -i /home/wash/.LOG//black.lst"
</snip>

2. What causes extranneous lockfile? I am attaching my recipe that gives that 
error and fails
to work...
I'll be glad if someone could help me rewrite it.

Thank you very much


-Wash

--
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