Rename *.csv.* files with mutilple extensions in Linux bash - bash

Question

I would like to rename files with multiple extensions (only the csv files) with .csv extension to the end.
example Input files in directory:
zebra.txt
sounds.pdf
input.csv
input.csv.aa
input.csv.ab .. ..
input.csv.zz
123.csv
123.csv.aa ...
123.csc.zz xxx.csv yyy.csv
All .csv. files are in the same format. I would like the output to be *.csv file with no further extensions
I would like to rename the files to keep the last part of extension to be swapped like below.
input.csv.aa to input_aa.csv
input.csv.ab to input_ab.csv ..
input.csv.zz to input_zz.csv
xxx.csv - will remain as is
yyy.csv - will remain as is
or
If we can combine to one file based on name, that is fine too
input.csv (combined all input.csv.aa,input.csv.ab, ..,input.csv.zz)
123.csv (combined all 123.csv.aa, .. , 123.csc.zz) xxx.csv yyy.csv

Answer 1

Try something like this for your first option:
find . -name "*.csv*" | \
sed -e 's/\(\(.*\)\.csv\(.*\)\)/\1|\2\3.csv/' | \
tr '|' '\n' | \
xargs -n 2 mv
This does:
Finds all the files with a .csv extension somewhere in the name, putting one filename per line
Changes the line to output the original name, then a pipe character (|), then a new filename with any additional extensions after .csv moved to come before the .csv (e.g. input.csv.aa becomes input.csv.aa|input.aa.csv)
Replace pipe with a newline
For every two lines, pass as arguments to mv to rename the files

Answer 2

To rename *.csv files:
find . -regex ".*\.csv\.[a-z]*$" -exec rename 's/(\.csv)\.([a-z]+)$/_$2$1/' {} \;
-regex pattern - file name matches regular expression pattern
rename perlexp - renames the filenames according to the Perl expression perlexp
To combine a separate group of files (let's say input.csv.aa,input.csv.ab, ..,input.csv.zz) into one file - use the following cat approach:
cat input.csv.* > input.csv