one line shell to output all combinations of letters in a word

Question

I have a word like:

fath

output all combinations of letters in a word like:

f
fa
fat
fath
ft
fth
fh

Those aren't all combinations, of course. Do you want this exact output or do you want all possible combinations? Also, what do you have so far? Which part of this is giving you trouble? — terdon, Jun 15 '20 at 13:36

z3rone · Accepted Answer · 2020-06-15T14:12:20.990

1

EDIT:

Here is a one line awk solution:

echo f a t h | awk '{for(i=0;i<2^NF;i++) { for(j=0;j<NF;j++) {if(and(i,(2^j))) printf "%s",$(j+1)} print ""}}'

Output


f
a
fa
t
ft
at
fat
h
fh
ah
fah
th
fth
ath
fath

(modified version of this power set implementation https://stackoverflow.com/questions/40966428/awk-power-set-implementation)

edited Jun 15 '20 at 14:12

answered Jun 15 '20 at 13:19

z3rone

62

Where is hat? Is the output inclomplete? – Panki Jun 15 '20 at 14:47
The command persists the order of the letters – z3rone Jun 15 '20 at 14:54
@Panki ath is present and the OP asked for combinations, not permutations. – Ed Morton Jun 15 '20 at 23:29
why is echo f a t h not echo fath – John Chen Jun 17 '20 at 02:43
the letters needs to be space separated for the awk script. You can add spaces to "fath" by piping it through sed -e 's/$.$/\1 /g' – z3rone Jun 17 '20 at 11:41

glenn jackman · Answer 2 · 2020-06-18T17:09:03.007

1

bash:

combos () {
    local word=$1
    local len=${#word}
    local first=${word:0:1}
    echo "$first"
    for ((i=1; i < len; i++ )); do
        for ((j=1; i+j <= len; j++ )); do
            echo "$first${word:i:j}"
        done
    done
}

then

$ combos fath
f
fa
fat
fath
ft
fth
fh

edited Jun 18 '20 at 17:09

answered Jun 15 '20 at 20:40

glenn jackman

85,964

1

That's missing f and combinations that don't include f, e.g. at. – Ed Morton Jun 15 '20 at 23:26
That's missing f – John Chen Jun 18 '20 at 16:20
@JohnChen, fixed. – glenn jackman Jun 18 '20 at 17:09

one line shell to output all combinations of letters in a word

2 Answers2