Code:
awk -F"\t" '{if ($2 !~ /[A-Za-z ]/) {print $2 "\t valid"; } else {print $2 "\t invalid";}}' filename
Output
Code:
123 valid
1 23 invalid
123AB invalid
ABD123 invalid
12345 valid
NOPE invalid
1234 invalid
or if you want to drop those which are alphanumberic,try
Code:
awk -F"\t" '$2 !~ /[A-Za-z ]/ { print $0 }' filename
