Iterate over letters in a for loop

Question

Is it possible to iterate over a list of letters, as followed:

aaaa, aaab, ..., aaaz, aaba, aabb, ..., aabz, ..., zzzy, zzzz

I know the syntax to iterate over the alphabet:

for i in {a..z}

but couldn't figure out a way to do the extended version...

Thanks in advance

Possible duplicate of [Looping through alphabets in Bash](https://stackoverflow.com/q/7300070/608639). — jww, Dec 25 '19 at 12:06

score 5 · Accepted Answer · answered Jun 18 '14 at 07:45

5

You could use brace expansion:

echo {a..z}{a..z}{a..z}{a..z}

Use it in a loop:

for i in {a..z}{a..z}{a..z}{a..z}; do
    echo $i
done

It would produce:

aaaa
aaab
aaac
aaad
aaae
...
zzzv
zzzw
zzzx
zzzy
zzzz

You can read more about combining and nesting brace expansions here.

answered Jun 18 '14 at 07:45

devnull

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Remember this is printing 26^4 lines though so may take a while and seem like its hung – Jun 18 '14 at 07:54

David C. Rankin · Answer 2 · 2014-06-18T07:49:56.027

Yes, BASH doesn't care what is contained in the sequence, as long as you give it the sequence.

for i in ducks geese swans; do echo $i; done
ducks
geese
swans

for building further with brace expansion, you just need to work on your brace statements:

for i in aaa{a..z}; do echo $i; done
aaaa
aaab
aaac
aaad
aaae
aaaf
aaag
aaah
aaai
aaaj
aaak
...

Take a look at brace expansion in man bash. You can use the above to satisfy your needs by a set of nested loops with differing levels of prefix for your expansion setups.

score 0 · Answer 3 · answered Jun 18 '14 at 07:43

0

I actually don't know bash well, but wouldn't that work?

// Pseudocode
for i in {a..z}
for j in {a..z}
for k in {a..z}
for l in {a..z}
echo $i$j$k$l

answered Jun 18 '14 at 07:43

Spook

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Iterate over letters in a for loop

3 Answers3