在Bash中,测试数组是否包含某个值的最简单方法是什么?


当前回答

The answer with most votes is very concise and clean, but it can have false positives when a space is part of one of the array elements. This can be overcome when changing IFS and using "${array[*]}" instead of "${array[@]}". The method is identical, but it looks less clean. By using "${array[*]}", we print all elements of $array, separated by the first character in IFS. So by choosing a correct IFS, you can overcome this particular issue. In this particular case, we decide to set IFS to an uncommon character $'\001' which stands for Start of Heading (SOH)

$ array=("foo bar" "baz" "qux")
$ IFS=$'\001'
$ [[ "$IFS${array[*]}$IFS" =~ "${IFS}foo${IFS}" ]] && echo yes || echo no
no
$ [[ "$IFS${array[*]}$IFS" =~ "${IFS}foo bar${IFS}" ]] && echo yes || echo no
yes
$ unset IFS

这解决了大多数假阳性问题,但需要一个好的IFS选择。

注意:如果之前设置了IFS,最好保存并重新设置,而不是使用未设置的IFS


相关:

访问bash命令行参数$@ vs $*

其他回答

如果您想做一个快速而复杂的测试,看看是否值得遍历整个数组以获得精确匹配,Bash可以像对待标量一样对待数组。测试标量中的匹配项,如果没有,则跳过循环节省时间。显然你会得到假阳性。

array=(word "two words" words)
if [[ ${array[@]} =~ words ]]
then
    echo "Checking"
    for element in "${array[@]}"
    do
        if [[ $element == "words" ]]
        then
            echo "Match"
        fi
    done
fi

这将输出“Checking”和“Match”。使用array=(word "two words" something),它只会输出"Checking"。使用array=(单词“two widgets”什么的)将没有输出。

这是一个小小的贡献:

array=(word "two words" words)  
search_string="two"  
match=$(echo "${array[@]:0}" | grep -o $search_string)  
[[ ! -z $match ]] && echo "found !"  

注意:这种方法不区分大小写“两个单词”,但在问题中不需要这样做。

以下是我对这个问题的看法。以下是简短的版本:

function arrayContains() {
        local haystack=${!1}
        local needle="$2"
        printf "%s\n" ${haystack[@]} | grep -q "^$needle$"
}

长一点的版本,我觉得看起来更舒服。

# With added utility function.
function arrayToLines() {
        local array=${!1}
        printf "%s\n" ${array[@]}
}

function arrayContains() {
        local haystack=${!1}
        local needle="$2"
        arrayToLines haystack[@] | grep -q "^$needle$"
}

例子:

test_arr=("hello" "world")
arrayContains test_arr[@] hello; # True
arrayContains test_arr[@] world; # True
arrayContains test_arr[@] "hello world"; # False
arrayContains test_arr[@] "hell"; # False
arrayContains test_arr[@] ""; # False

结合Beorn Harris和loentar的回答,我们得出了一个更有趣的单行测试:

delim=$'\x1F' # define a control code to be used as more or less reliable delimiter
if [[ "${delim}${array[@]}${delim}" =~ "${delim}a string to test${delim}" ]]; then
    echo "contains 'a string to test'"
fi

它不使用额外的函数,不替换测试,并添加了额外的保护,防止使用控制代码作为分隔符偶尔出现错误匹配。


UPD:感谢@ChrisCogdon的注意,这个错误的代码被重写并以https://stackoverflow.com/a/58527681/972463的形式发布。

保持简单:

Array1=( "item1" "item2" "item3" "item-4" )
var="item3"

count=$(echo ${Array1[@]} | tr ' ' '\n' | awk '$1 == "'"$var"'"{print $0}' | wc -l)
[ $count -eq 0 ] && echo "Not found" || echo "found"