Question

I’m trying to learn bash string handling. How do I create a bash script which is equivalent to this Java code snippet?

String symbols = 'abcdefg12345_'; for (char i : symbols.toCharArray()) {     for (char j : symbols.toCharArray()) {         System.out.println(new StringBuffer().append(i).append(j));     } } 

The output of the above code snippet starts with:

aa ab ac ad ae af 

And ends with:

_g _1 _2 _3 _4 _5 __ 

My goal is to have a list of allowed characters (not necessarily the ones above) and print out all the permutations of length 2. If it is possible I would like a solution which relies solely on bash and doesn’t require anything else installed.

Edit: Just a little follow up question: Is there a way to do this with a string without spaces separating sub-strings? Like LIST=’abcdef12345_’?

Answer 1

That is so simple, Bash does it in the input parser. No code required. Try:

echo {a,b,c,d,e,f,g,1,2,3,4,5,_}{a,b,c,d,e,f,g,1,2,3,4,5,_} 

You might need a second pass to split it into lines, though.

Or, you could of course use a couple of nested loops like in your example:

LIST='a b c d e f 1 2 3 4 5 _'; for a in $LIST ; do     for b in $LIST ; do         echo $a$b;     done; done