Rearrange columns using cut

Question

I am having a file in the following format

Column1    Column2
str1       1
str2       2
str3       3

I want the columns to be rearranged. I tried below

Answer 1

You can use Perl for that:

perl -ane 'print "$F[1] $F[0]\n"' < file.txt

• -e option means execute the command after it
• -n means read line by line (open the file, in this case STDOUT, and loop over lines)
• -a means split such lines to a vector called @F ("F" - like Field). Perl indexes vectors starting from 0 unlike cut which indexes fields starting form 1.
• You can add -F pattern (with no space between -F and pattern) to use pattern as a field separator when reading the file instead of the default whitespace

The advantage of running perl is that (if you know Perl) you can do much more computation on F than rearranging columns.