如何从 Bash 中的数组中获取唯一值? [英] How can I get unique values from an array in Bash?

问题描述

我遇到了与 此处.

我有一个包含 aa ab aa ac aa ad 等的数组.现在我想从这个数组中选择所有唯一的元素.想，这会很简单 sort |uniq 或 sort -u 正如他们在另一个问题中提到的那样，但数组中没有任何变化......代码是:

I have an array which contains aa ab aa ac aa ad, etc. Now I want to select all unique elements from this array. Thought, this would be simple with sort | uniq or with sort -u as they mentioned in that other question, but nothing changed in the array... The code is:

echo `echo "${ids[@]}" | sort | uniq`

我做错了什么?

推荐答案

有点 hacky，但这应该可以:

A bit hacky, but this should do it:

echo "${ids[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' '

要将排序后的唯一结果保存回数组，请执行数组分配:

To save the sorted unique results back into an array, do Array assignment:

sorted_unique_ids=($(echo "${ids[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' '))

如果你的 shell 支持 herestrings (bash 应该)，您可以将 echo 进程更改为:

If your shell supports herestrings (bash should), you can spare an echo process by altering it to:

tr ' ' '\n' <<< "${ids[@]}" | sort -u | tr '\n' ' '

截至 2021 年 8 月 28 日的说明:

根据ShellCheck wiki 2207 a read -a 应使用管道以避免分裂.因此，在 bash 中，命令将是:

According to ShellCheck wiki 2207 a read -a pipe should be used to avoid splitting. Thus, in bash the command would be:

IFS=""读取 -r -a ids <<<"$(echo "${ids[@]}" | tr ' ' '\n' | sort -u | tr '\n' ' ')"

或

IFS=""读取 -r -a ids <<<"$(tr ' ' '\n' <<< "${ids[@]}" | sort -u | tr '\n' ' ')"

输入:

ids=(aa ab aa ac aa ad)

输出:

aa ab ac ad

说明:

• "${ids[@]}" - 用于处理 shell 数组的语法，无论是用作 echo 的一部分还是用作 herestring.@ 部分表示数组中的所有元素"
• tr ' ' '\n' - 将所有空格转换为换行符.因为你的数组被 shell 看作是一行上的元素，用空格分隔；并且因为 sort 期望输入在不同的行上.
• sort -u - 排序并只保留唯一元素
• tr '\n' ' ' - 将我们之前添加的换行符转换回空格.
• $(...) - 命令替换
• 旁白:tr ' ' '\n' <<<${ids[@]}" 是一种更有效的方式: echo ${ids[@]}"|tr ' ' '\n'

• "${ids[@]}" - Syntax for working with shell arrays, whether used as part of echo or a herestring. The @ part means "all elements in the array"
• tr ' ' '\n' - Convert all spaces to newlines. Because your array is seen by shell as elements on a single line, separated by spaces; and because sort expects input to be on separate lines.
• sort -u - sort and retain only unique elements
• tr '\n' ' ' - convert the newlines we added in earlier back to spaces.
• $(...) - Command Substitution
• Aside: tr ' ' '\n' <<< "${ids[@]}" is a more efficient way of doing: echo "${ids[@]}" | tr ' ' '\n'

这篇关于如何从 Bash 中的数组中获取唯一值?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！