Select subdomains using print command - linux

Question

cat a.txt
a.b.c.d.e.google.com
x.y.z.google.com
rev a.txt | awk -F. '{print $2,$3}' | rev
This is showing:
e google
x google
But I want this output
a.b.c.d.e.google
b.c.d.e.google
c.d.e.google
e.google
x.y.z.google
y.z.google
z.google

Answer 1

With your shown samples, please try following awk code. Written and tested in GNU awk should work in any awk.
awk '
BEGIN{
FS=OFS="."
}
{
nf=NF
for(i=1;i<(nf-1);i++){
print
$1=""
sub(/^[[:space:]]*\./,"")
}
}
' Input_file

Answer 2

Here is one more awk solution:
awk -F. '{while (!/^[^.]+\.[^.]+$/) {print; sub(/^[^.]+\./, "")}}' file
a.b.c.d.e.google.com
b.c.d.e.google.com
c.d.e.google.com
d.e.google.com
e.google.com
x.y.z.google.com
y.z.google.com
z.google.com

Answer 3

Using sed
$ sed -En 'p;:a;s/[^.]+\.(.*([^.]+\.){2}[[:alpha:]]+$)/\1/p;ta' input_file
a.b.c.d.e.google.com
b.c.d.e.google.com
c.d.e.google.com
d.e.google.com
e.google.com
x.y.z.google.com
y.z.google.com
z.google.com

Answer 4

Using bash:
IFS=.
while read -ra a; do
for ((i=${#a[#]}; i>2; i--)); do
echo "${a[*]: -i}"
done
done < a.txt
Gives:
a.b.c.d.e.google.com
b.c.d.e.google.com
c.d.e.google.com
d.e.google.com
e.google.com
x.y.z.google.com
y.z.google.com
z.google.com
(I assume the lack of d.e.google.com in your expected output is typo?)

Answer 5

For a shorter and arguably simpler solution, you could use Perl.
To auto-split the line on the dot character into the #F array, and then print the range you want:
perl -F'\.' -le 'print join(".", #F[0..$#F-1])' a.txt
-F'\.' will auto-split each input line into the #F array. It will split on the given regular expression, so the dot needs to be escaped to be taken literally.
$#F is the number of elements in the array. So #F[0..$#F-1] is the range of elements from the first one ($F[0]) to the penultimate one. If you wanted to leave out both "google" and "com", you would use #F[0..$#F-2] etc.