Remove certain column with numeric value

Shell Programming and Scripting
1

I have file1.txt

LBP298W2,300,-18,-115,-12,-105
LBP298W2,300,-18,-115,LBP298W3,300
LBP298W3,300,-18,-115,-12,-105

---------- Post updated at 03:35 AM ---------- Previous update was at 03:34 AM ----------

i want to remove every line with non numeric value in column 5

expected result

LBP298W2,300,-18,-115,-12,-105
LBP298W3,300,-18,-115,-12,-105
2

Can try if this is sufficient:

$ awk -F, '$5 !~ /[a-zA-Z]/' infile
LBP298W2,300,-18,-115,-12,-105
LBP298W3,300,-18,-115,-12,-105
3

If zaxxon's proposal isn't sufficient for your purposes, this is more precise:

awk -F, '$5 ~ /^[-+]?[[:digit:]]+$/' file1.txt
4

With Perl (core modules):

perl -F, '-MScalar::Util qw(looks_like_number)' -lane'
  print if looks_like_number $F[4]
  ' infile
5

so much thank you...mr Zax, Don,& Radoulov