HackerRank Tr Command #3 problem solution

In this HackerRank 'Tr' Command #3 problem solution The 'tr' command is a useful translation utility in linux.

'e' being transformed to 'E'

$ echo "Hello" | tr "e" "E"

HEllo

Spaces being transformed to hyphens

$ echo "Hello how are you" | tr " " '-'

Hello-how-are-you

Digits (numerals) being deleted

$ echo "Hello how are you 1234" | tr -d [0-9]

Hello how are you 

In a given fragment of text, replace all sequences of multiple spaces with just one space.

Input Format

A block of ASCII text.

Output Format

Replace all sequences of multiple spaces with just one space.

Problem solution.

tr -s ' '

Second solution.

tr -s "[:space:]"

Third solution.

while true 
do 
    read -s input 
    echo  $input | tr -s [:space:] ' '
    echo ''
    if [[ -z "$input" ]]
    then 
        break
    fi 
done