Converting 2 or more spaces to a single tab

Shell Programming and Scripting
1

I'm new to bash and want to know a simple sed, awk, or grep script that will find all instances of 2 or more spaces and convert them to a single tab. Thanks for the help in advance.

2

In the command mode

:1,$ s/[ ][ ][ ]*/<tab>/g

or using sed

cat inputfile | sed 's/[ ][ ][ ]*/<tab>/g' > outputfile