在 Bash 循环中生成 IP 地址列表
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Generating a list of IP addresses in a Bash loop
提问by K.U
I need a list of IP addresses from 130.15.0.0 to 130.15.255.255. I tried this but I realized it will create 255 lists. Can anyone please help me figure this out?
我需要一个从 130.15.0.0 到 130.15.255.255 的 IP 地址列表。我试过了，但我意识到它会创建 255 个列表。任何人都可以帮我解决这个问题吗？
for (( i = 0; i <= 255; i++)) ; do
for (( j = 0; j <= 255; j++)) ; do
LIST="$LIST 130.15.$i.$j"
done
done
回答by Benjamin W.
I'd say that your approach works, but it is very slow1. You can use brace expansion instead:
我会说你的方法有效，但速度很慢1。您可以改用大括号扩展：
echo 135.15.{0..255}.{0..255}
Or, if you want the result in a variable, just assign:
或者，如果你想要一个变量的结果，只需分配：
list=$(echo 135.15.{0..255}.{0..255})
If you want the addresses in an array, you can skip the echoand command substitution:
如果你想要数组中的地址，你可以跳过echo和命令替换：
list=(135.15.{0..255}.{0..255})
Now, listis a proper array:
现在，list是一个合适的数组：
$ echo "${list[0]}" # First element
135.15.0.0
$ echo "${list[@]:1000:3}" # Three elements in the middle
135.15.3.232 135.15.3.233 135.15.3.234
Comments on your code:
对您的代码的评论：
Instead of
list="$list new_element"it is easier to append to a string with
list+=" new_element"If you wanted to append to an array in a loop, you'd use
list+=("new_element")- Uppercase variable names are not recommended as they're more likely to clash with environment variables (see POSIX spec, paragraph four)
代替
list="$list new_element"附加到字符串更容易
list+=" new_element"如果你想在循环中附加到一个数组，你会使用
list+=("new_element")- 不建议使用大写变量名，因为它们更有可能与环境变量发生冲突（请参阅POSIX 规范，第 4 段）
1In fact, on my machine, it takes almost six minutes – the brace expansion takes less than 0.1 seconds!
1事实上，在我的机器上，几乎需要 6 分钟 - 支架扩展只需不到 0.1 秒！
