Shell Programming and Scripting

randomize=`cat /dev/urandom | tr -dc "a-z0-9" | fold -w 6 | head -n 1`

sed -i 's/blah/blah?$randomize/g' /home/test.html

#!/usr/bin/env ksh

awk  -v pattern="${1:-boo}" '
    function gen(       j, i, c )       # gen random replacement words
    {
        ridx = 0;
        for( i = 0; i < 500; i++ )
        {
            for( j = 0; j < word_len; j++ )
                rword[i] = rword[i] substr( soup, ((int(rand( ) *1000)) % length( soup )) + 1, 1 );
        }
    }
    BEGIN {
        soup = "abcdefghijklmnopqrstuvwxyz01234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";   # xlation
        word_len = 5;       # random word size
        gen();
     }

    {
        while( sub( pattern, "<goop>" rword[ridx++], $0 ) );    # assume <goop> is not in any input data nor the pattern
            if( ridx >= 500 )
                gen();
        gsub( "<goop>", pattern "?" );
        print;
    }
' "$@"

Now is the time to test
Forever is the time to try the programme
now the final sentance is here the end.

Now is the?LC00s time to test
Forever is the?ON2nl time to try the?5berE programme
now the?jn1BE final sentance is here the?cJod1 end.

# Random character generator
randomizer()
{
randomize=`cat /dev/urandom | tr -dc "a-z0-9" | fold -w 6 | head -n 1`
result=$randomize
}

randomizer
echo $result

randomizer
echo $result