如何在鱼壳中生成字母序列表

Question

In bash you can generate letter sequence easily as "{a..z}", for example

$ echo {a..z}
a b c d e f g h i j k l m n o p q r s t u v w x y z

How to do that in the fish shell instead?

Answer 1

Fish doesn't support ranges in brace expansion , only comma-separated values: {a,b,c} .

Thus, we are forced to search for a command capable of generating such sequence. For example, you can use Perl:

for c in (perl -e '$,="\n"; print ("a" .. "z")')
  printf ">> %s\n" "$c"
end

where $, is the output field separator.

Output

>> a
>> b
...(skipped)
>> y
>> z

You may find this table useful.

Answer 2

One way is to use printf and seq.

echo -e (printf '\\\x%x\n' (seq 97 122))

This works by generating "\\x61 \\x62 \\x63 ... \\x7a" which is then interpreted by "echo -e" as hex character codes.

Answer 3

Specifically to generate az sequence you can loop with, I think the most elegant and concise solution is to directly use bash with fmt (which is available in most unix-like environment). You don't even need Perl and its more readable:

for c in (bash -c "echo {a..z}" | fmt -w1)
    echo "hello $c"
end

The logic goes like this:

1. The for-loop in fish shell loops through both array values and lines. If you can generate az each in its separate line, you can loop with that in fish.

2. The command bash -c "echo {a..z}" would give you a single long string in fish:

    abcdefghijklmnopqrstu vwxyz

3. The command fmt -w1 would cut the space-separated strings into lines.

Result:

hello a
hello b
hello c
... (skipped)
hello z

This is amazing because you can take advantage of the same principle to reuse bash syntax in fish. Seems really flexible to me :-)

Answer 4

Linux has the seq command for this, and it works with fishshell:

$ for f in (seq 1 10)
    echo $f
end
1
2
3
4
5
6
7
8
9
10
$