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

问题描述

我有与我有一个包含aa ab aa ac aa ad等的数组. 现在，我想从该数组中选择所有唯一元素. 想想，使用sort | uniq或sort -u就像在另一个问题中提到的那样简单，但是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`

我在做什么错了?

推荐答案

有点hacky，但这应该可以做到:

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' ' '))

如果您的外壳支持此处字符串(应为bash)，则可以将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' ' '

输入:

ids=(aa ab aa ac aa ad)

输出:

aa ab ac ad

说明:

• "${ids[@]}"-使用shell数组的语法，无论是作为echo的一部分还是在此处使用. @部分的意思是数组中的所有元素"
• tr ' ' '\n'-将所有空格转换为换行符.因为您的数组被shell视为一行上的元素，并用空格分隔；并且因为sort期望输入在单独的行上.
• sort -u-仅排序和保留唯一元素
• tr '\n' ' '-将我们之前添加的换行符转换回空格.
• $(...)-命令替换
• 此外:tr ' ' '\n' <<< "${ids[@]}"是一种更有效的处理方式: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'

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