Shell Programming and Scripting

hi,

i am running this command inside the script

var=`grep -il $1 "${logdir}"* | xargs grep -ivl adding | xargs grep -ivl equation | xargs ls -ctr | tail -1`

in that grep will find the latest logfile for the variable "$"

if it fnd the logfile, then it reutrns the filename to the var
if it not found it should return ' ' (NULL )

but in above command ... if it not found it is returning 1

could someone please help me in that

what could be the reason for that ?
how to fix it

Does adding an -r to the last xargs (for the ls command) help at all?