Script to group together similar file names

In this post, I'd like to share a little script I wrote to club together similarly named contents in a file. The query was posted on social media & I'm sharing the same answer here which I wrote there.

So, here' s the problem statement:

Have a look at the below file testfile:

[root@centops ~]# cat testfile
test1.txt
test2.html
test4.sql
test3.txt
test4.txt
test5.sql
test7.html
test5.txt
test9.sql

The file contains names ending with txt, sql & html. What if I needed to group together the names ending with txt & similarly for sql & html. Here is a simple script which does exactly that:

[root@centops ~]# cat group.sh

#!/bin/bash

for i in $(< testfile)

do

##separate the file names into tmp files##

 r1=$(echo $i | grep txt$);  echo $r1 | sed '/^$/d' >> tmp1

 r2=$(echo $i | grep sql$);  echo $r2 | sed '/^$/d' >> tmp2

 r3=$(echo $i | grep html$); echo $r3  | sed '/^$/d' >> tmp3

done

##group the contents##

cat tmp1 tmp2 tmp3 >> result.txt

cat result.txt

rm -f tmp1 tmp2 tmp3

Here's the script output:

[root@centops ~]# ./group.sh

test1.txt

test3.txt

test4.txt

test5.txt

test4.sql

test5.sql

test9.sql

test2.html

test7.html

This particular script may cater to a very specific requirement but this is some food or thought. Through in a couple of variable to substitute the type of entities that need to be grouped & a parameter substitution for the file name & this little script may do a lot.