reverse order in a csv

You could use awk:

awk  'BEGIN{
     FS=OFS=","               # set the field delimiter
   }
   NF{                        # execute only on non empty line
      for(i=NF;i>1;i--)       # loop through all element except the first one
         printf "%s", $i OFS; # print the parameter together with the comma 
      printf "%s", $1 "\n"    # print last element
   }' input.csv

CSV can't always be processed by simply splitting by commas, line by line, since fields may sometimes have commas themselves, or newlines. To be able to include those characters, fields must be quoted. You need quotes to include quote characters too.

This is a simple solution you can call from the shell that uses a proper csv parser:

ruby -e 'require "csv"; CSV.filter(&:reverse!)' < input.csv > output.csv

If you don't have ruby, this works with both python 2 and 3.

python -c $'import csv; import sys\nfor r in csv.reader(sys.stdin): r.reverse(); csv.writer(sys.stdout).writerow(r)' < input.csv > output.csv

Here it is in multiple lines:

python < input.csv > output.csv -c '
import csv
import sys

for r in csv.reader(sys.stdin):
  r.reverse()
  csv.writer(sys.stdout).writerow(r)
'

Here are some examples where this will work where solutions with simple comma splitting won't work:

input.csv

1,"2,3"

output.csv

"2,3",1

input.csv

1,"
2"

output.csv

"
2",1

perl -l -a -F, -n -e 'print join ("," , reverse  @F)'  input.csv

awk -F, '{for(i=NF;i>=1;i--)printf("%s,",$i);printf "\n"}' input.txt | sed "s/$,//"