Shell Programming and Scripting

#!/bin/bash
# scriptname: recast_string
# purpose: recast a string randomly like this "abc123" --> "21a3cb" or "a31b2c"

function recast()
{
        local original_string=$1
        local changed_string=${original_string}
        local recast_string=
        while [[ ${i:=0} < ${#original_string} ]]
        do
                random_char=${changed_string:$(($RANDOM%${#changed_string})):1}
                changed_string=${changed_string/$random_char/}
                echo ${#changed_string}
                recast_string=${recast_string}${random_char}
                ((i++))
        done
        echo "$1 has been recast to ${recast_string}."
}

recast $1
exit 0

sh -x recast_string j138sd113
+ recast j138sd113
+ local original_string=j138sd113
+ local changed_string=j138sd113
+ local recast_string=
+ [[ 0 < 9 ]]
+ random_char=8
+ changed_string=j13sd113
+ echo 8
8
+ recast_string=8
+ (( i++ ))
+ [[ 1 < 9 ]]
+ random_char=s
+ changed_string=j13d113
+ echo 7
7
+ recast_string=8s
+ (( i++ ))
...... (omitted sth here)
+ [[ 8 < 9 ]]
+ random_char=3
+ changed_string=
+ echo 0
0
+ recast_string=8sd311j13
+ (( i++ ))
+ [[ 9 < 9 ]]
+ echo 'j138sd113 has been recast to 8sd311j13.'
j138sd113 has been recast to 8sd311j13.

 sh -x recast_string j138sd1135
+ recast j138sd1135
+ local original_string=j138sd1135
+ local changed_string=j138sd1135
+ local recast_string=
+ [[ 0 < 10 ]]
+ random_char=8
+ changed_string=j13sd1135
+ echo 9
9
+ recast_string=8
+ (( i++ ))
+ [[ 1 < 10 ]]
+ random_char=1
+ changed_string=j3sd1135
+ echo 8
8
+ recast_string=81
+ (( i++ ))
+ [[ 2 < 10 ]]
+ echo 'j138sd1135 has been recast to 81.'
j138sd1135 has been recast to 81.

./recast_string 1 3 5 
./recast_string "1 3 5"
./recast_string '1 3 5'