检查索引或数组中的一个关键的最简单的方法？ [英] Easiest way to check for an index or a key in an array?

问题描述

使用：

set -o nounset

1）有一个索引数组，如：

1) Having an indexed array like:

myArray=( "red" "black" "blue" )

这是检查是否元素1设置最短的方法是什么？结果
我有时会使用以下命令：

Which is the shortest way to check if element 1 is set?
I sometimes use the following:

test "${#myArray[@]}" -gt "1" && echo "1 exists" || echo "1 doesn't exist"

我想知道是否有pferred一个$ P $。
结果
结果
2）如何处理非连续的索引？

I would like to know if there's a preferred one.

2) How to deal with non-consecutive indexes?

myArray=()
myArray[12]="red"
myArray[51]="black"
myArray[129]="blue"

如何快速检查五一已被设置为例子吗？
结果
结果
3）如何处理关联数组？

How to quick check that '51' is already set for example?

3) How to deal with associative arrays?

declare -A myArray
myArray["key1"]="red"
myArray["key2"]="black"
myArray["key3"]="blue"

如何快速检查键2已用于例子吗？
结果
结果
谢谢

How to quick check that 'key2' is already used for example?

Thanks

EDITED 结果
最简单的方法似乎对我说：

EDITED
The simplest way seems to me:

if test "${myArray['key_or_index']+isset}"
    then
        echo "yes"
    else
        echo "no"
fi;

这同时适用于索引和关联数组。有没有一套-o nounset显示错误。结果
由于doubleDown为headup。

This works for both indexed and associative arrays. No errors shown with set -o nounset.
Thanks to doubleDown for the headup.

推荐答案

要检查元素设置（适用于索引和关联数组）

To check if the element is set (applies to both indexed and associative array)

[ ${array[key]+abc} ] && echo "exists"

基本上什么 $ {数组[键] + ABC} 所做的就是

• 如果阵列[关键] 设置，返回 ABC


• 如果阵列[关键] 没有设置，返回任何

• if array[key] is set, return abc
• if array[key] is not set, return nothing

---

参考文献：

---

References:

1. 请参见参数扩展猛砸手册和在稍微注意一下

1. See Parameter Expansion in Bash manual and the little note

如果结肠被省略，操作者仅测试生存[中的参数的]

if the colon is omitted, the operator tests only for existence [of parameter]

这答案其实是改编自答案为这太问题：<一href=\"http://stackoverflow.com/questions/228544/how-to-tell-if-a-string-is-not-defined-in-a-bash-shell-script\">How判断一个字符串是不是在bash shell脚本定义？

This answer is actually adapted from the answers for this SO question: How to tell if a string is not defined in a bash shell script?

一个包装函数：

exists(){
  if [ "$2" != in ]; then
    echo "Incorrect usage."
    echo "Correct usage: exists {key} in {array}"
    return
  fi   
  eval '[ ${'$3'[$1]+muahaha} ]'  
}

例如

if ! exists key in array; then echo "No such array element"; fi 

这篇关于检查索引或数组中的一个关键的最简单的方法？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！