$ echo 'foo:123:bar:789' | awk -F: '{print $2,$3}'
123 bar

$ # second field where input field separator is :
$ echo 'foo:123:bar:789' | awk -F: '{print $2}'
123

$ # last field
$ echo 'foo:123:bar:789' | awk -F: '{print $NF}'
789

$ # first and last field
$ # note the use of , and space between output fields
$ echo 'foo:123:bar:789' | awk -F: '{print $1, $NF}'
foo 789

$ # second last field
$ echo 'foo:123:bar:789' | awk -F: '{print $(NF-1)}'
bar

$ # use quotes to avoid clashes with shell special characters
$ echo 'one;two;three;four' | awk -F';' '{print $3}'
three

$ echo 'Sample123string54with908numbers' | awk -F'[0-9]+' '{print $2}'
string

$ grep -rn "Hello" *