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
$ myarray=(one two three)
$ case "${myarray[@]}" in *"two"*) echo "found" ;; esac
found
其他回答
我通常只使用:
inarray=$(echo ${haystack[@]} | grep -o "needle" | wc -w)
非零值表示找到了匹配。
... 实际上,为了解决它不能与needle1和needle2工作的问题,如果你只想要一个精确匹配,没有更多,没有更少,只需在-o后面添加一个w标志,用于整个单词匹配:
inarray=$(echo ${haystack[@]} | grep -ow "needle" | wc -w)
下面的代码检查给定值是否在数组中,并返回其从零开始的偏移量:
A=("one" "two" "three four")
VALUE="two"
if [[ "$(declare -p A)" =~ '['([0-9]+)']="'$VALUE'"' ]];then
echo "Found $VALUE at offset ${BASH_REMATCH[1]}"
else
echo "Couldn't find $VALUE"
fi
匹配是在完整的值上完成的,因此设置VALUE="three"将不匹配。
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 [[ $element == "words" ]]
then
echo "Match"
fi
done
fi
这将输出“Checking”和“Match”。使用array=(word "two words" something),它只会输出"Checking"。使用array=(单词“two widgets”什么的)将没有输出。
@ghostdog74关于使用大小写逻辑检查数组包含特定值的回答的一个小补充:
myarray=(one two three)
word=two
case "${myarray[@]}" in ("$word "*|*" $word "*|*" $word") echo "found" ;; esac
或者打开extglob选项,你可以这样做:
myarray=(one two three)
word=two
shopt -s extglob
case "${myarray[@]}" in ?(*" ")"$word"?(" "*)) echo "found" ;; esac
我们也可以用if语句:
myarray=(one two three)
word=two
if [[ $(printf "_[%s]_" "${myarray[@]}") =~ .*_\[$word\]_.* ]]; then echo "found"; fi
借鉴Dennis Williamson的答案,下面的解决方案结合了数组、shell-safe引号和正则表达式,以避免需要:遍历循环;使用管道或其他子过程;或者使用非bash实用程序。
declare -a array=('hello, stack' one 'two words' words last)
printf -v array_str -- ',,%q' "${array[@]}"
if [[ "${array_str},," =~ ,,words,, ]]
then
echo 'Matches'
else
echo "Doesn't match"
fi
上面的代码通过使用Bash正则表达式来匹配数组内容的字符串化版本。有六个重要的步骤来确保正则表达式匹配不会被数组中的值的巧妙组合所欺骗:
Construct the comparison string by using Bash's built-in printf shell-quoting, %q. Shell-quoting will ensure that special characters become "shell-safe" by being escaped with backslash \. Choose a special character to serve as a value delimiter. The delimiter HAS to be one of the special characters that will become escaped when using %q; that's the only way to guarantee that values within the array can't be constructed in clever ways to fool the regular expression match. I choose comma , because that character is the safest when eval'd or misused in an otherwise unexpected way. Combine all array elements into a single string, using two instances of the special character to serve as delimiter. Using comma as an example, I used ,,%q as the argument to printf. This is important because two instances of the special character can only appear next to each other when they appear as the delimiter; all other instances of the special character will be escaped. Append two trailing instances of the delimiter to the string, to allow matches against the last element of the array. Thus, instead of comparing against ${array_str}, compare against ${array_str},,. If the target string you're searching for is supplied by a user variable, you must escape all instances of the special character with a backslash. Otherwise, the regular expression match becomes vulnerable to being fooled by cleverly-crafted array elements. Perform a Bash regular expression match against the string.