UNIX shell: sort a string by word length and by ASCII order ignoring case

Question

I would like to sort a string by length and then by ASCII order(upper and lower case are equal) with a unix command.

string = [a-z][A-Z][0-9]

For example:

"A a b B cc ca cd" : 
=> A a b B
=> ca cc cd

"Hello stackoverflow how are you today"
=> are how you
=> Hello today
=> stackoverflow

Answer 1

I wrote an ugly (maybe) awk|sort|awk line to do the job. it could be done in one awk process too, however, I am a bit lazy, just go to the dirty and quick way.

echo yourStr|awk '{
split($0,o); for(x in o) print length(o[x]),o[x]}'|sort -n|awk '!p{printf $2;p=$1;next}$1==p{printf " "$2}$1!=p{printf "\n"$2;p=$1}' 

let's take an example:

"Hello stackoverflow how are you today foo bar xoo yoo ooo"

try with above line:

kent$  echo "Hello stackoverflow how are you today foo bar xoo yoo ooo"|awk '{
split($0,o); for(x in o) print length(o[x]),o[x]}'|sort -n|awk '!p{printf $2;p=$1;next}$1==p{printf " "$2}$1!=p{printf "\n"$2;p=$1}'
are bar foo how ooo xoo yoo you
Hello today
stackoverflow     

test with your first example:

kent$  echo "A a b B cc ca cd" |awk '{
pipe quote> split($0,o); for(x in o) print length(o[x]),o[x]}'|sort -n|awk '!p{printf $2;p=$1;next}$1==p{printf " "$2}$1!=p{printf "\n"$2;p=$1}' 
a A b B
ca cc cd