Eight Ways to Convert Tabs to Spaces

A collection of various ways to convert tabs to spaces in Unix/Linux/OS X with standard programs and utilities.

#1 expand/unexpand utilities
expand < input.txt > output.txt

#2 Sed
sed 's/\t/ /g' < input.txt > output.txt

#3 Awk
awk '{ gsub(/\t/, "  "); print }' < input.txt > output.txt

#4 Perl
perl -pe 's/\t/  /g' < input.txt > output.txt

#5 Ruby
ruby -pe '$_.gsub!(/\t/, "  ")' < input.txt > output.txt

#6a Vim editor
:set expandtab
:%retab! 

#6b Vim editor
:%s/\t/  /g

#7 Emacs editor
Set 'indent-tabs-mode' to nil to have tabs automatically converted to spaces.
To convert a region, "M-x untabify" will change tabs to spaces and "M-x tabify" will do the inverse.

#8 cut
cut -f1- --output-delimiter='  ' < input.txt > output.txt