Randomly shuffling lines in Linux / Bash

Question

I have some files in linux. For example 2 and i need shuffling the files in one file.

For example

$cat file1
line 1
line 2
line 3
line 4
line 5
line          


        

Answer 1

This worked for me. It employs the Fisher-Yates shuffle.

randomize()
{   
    arguments=("$@")
    declare -a out
    i="$#"
    j="0"

while [[ $i -ge "0" ]] ; do
    which=$(random_range "0" "$i")
    out[j]=${arguments[$which]}
    arguments[!which]=${arguments[i]}
    (( i-- ))
    (( j++ ))
done
echo ${out[*]}
}


random_range()
{
    low=$1
    range=$(($2 - $1))
    if [[ range -ne 0 ]]; then
        echo $(($low+$RANDOM % $range))
    else
        echo "$1"
    fi
}

Answer 2

It is clearly biased rand (like half the time the list will start with the first line) but for some basic randomization with just bash builtins I guess it is fine? Just print each line yes/no then print the rest...

shuffle() {
    local IFS=$'\n' tail=
    while read l; do
        if [ $((RANDOM%2)) = 1 ]; then
            echo "$l"
        else
            tail="${tail}\n${l}"

        fi
    done < $1
    printf "${tail}\n"
}