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
如何检查一个Bash数组是否包含一个值
假阳性匹配
array=(a1 b1 c1 d1 ee)
[[ ${array[*]} =~ 'a' ]] && echo 'yes' || echo 'no'
# output:
yes
[[ ${array[*]} =~ 'a1' ]] && echo 'yes' || echo 'no'
# output:
yes
[[ ${array[*]} =~ 'e' ]] && echo 'yes' || echo 'no'
# output:
yes
[[ ${array[*]} =~ 'ee' ]] && echo 'yes' || echo 'no'
# output:
yes
精确匹配
为了寻找精确匹配,你的正则表达式模式需要在值的前后添加额外的空格,如(^|[[:space:]])" value "($|[[:space:]])
# Exact match
array=(aa1 bc1 ac1 ed1 aee)
if [[ ${array[*]} =~ (^|[[:space:]])"a"($|[[:space:]]) ]]; then
echo "Yes";
else
echo "No";
fi
# output:
No
if [[ ${array[*]} =~ (^|[[:space:]])"ac1"($|[[:space:]]) ]]; then
echo "Yes";
else
echo "No";
fi
# output:
Yes
find="ac1"
if [[ ${array[*]} =~ (^|[[:space:]])"$find"($|[[:space:]]) ]]; then
echo "Yes";
else
echo "No";
fi
# output:
Yes
有关更多用法示例,示例的来源在这里
其他回答
这种方法的优点是不需要遍历所有元素(至少不是显式地)。但是由于array.c中的array_to_string_internal()仍然循环遍历数组元素并将它们连接到一个字符串中,因此它可能并不比所提出的循环解决方案更有效,但它更具可读性。
if [[ " ${array[*]} " =~ " ${value} " ]]; then
# whatever you want to do when array contains value
fi
if [[ ! " ${array[*]} " =~ " ${value} " ]]; then
# whatever you want to do when array doesn't contain value
fi
请注意,如果您正在搜索的值是带有空格的数组元素中的某个单词,则会给出假阳性。例如
array=("Jack Brown")
value="Jack"
正则表达式将“Jack”视为在数组中,即使它不在数组中。所以你必须改变IFS和正则表达式上的分隔符如果你仍然想使用这个解决方案,就像这样
IFS="|"
array=("Jack Brown${IFS}Jack Smith")
value="Jack"
if [[ "${IFS}${array[*]}${IFS}" =~ "${IFS}${value}${IFS}" ]]; then
echo "true"
else
echo "false"
fi
unset IFS # or set back to original IFS if previously set
这将打印“false”。
显然,这也可以用作测试语句,允许将其表示为一行程序
[[ " ${array[*]} " =~ " ${value} " ]] && echo "true" || echo "false"
我有这样的情况,我必须检查一个ID是否包含在另一个脚本/命令生成的ID列表中。 我的工作如下:
# the ID I was looking for
ID=1
# somehow generated list of IDs
LIST=$( <some script that generates lines with IDs> )
# list is curiously concatenated with a single space character
LIST=" $LIST "
# grep for exact match, boundaries are marked as space
# would therefore not reliably work for values containing a space
# return the count with "-c"
ISIN=$(echo $LIST | grep -F " $ID " -c)
# do your check (e. g. 0 for nothing found, everything greater than 0 means found)
if [ ISIN -eq 0 ]; then
echo "not found"
fi
# etc.
你也可以像这样缩短/压缩它:
if [ $(echo " $( <script call> ) " | grep -F " $ID " -c) -eq 0 ]; then
echo "not found"
fi
在我的例子中,我正在运行jq来过滤一些JSON的ID列表,然后必须检查我的ID是否在这个列表中,这对我来说是最好的。 它不适用于手动创建的LIST=("1" "2" "4")类型的数组,而是用于换行分隔的脚本输出。
附言:不能评论一个答案,因为我是相对较新的…
containsElement () { for e in "${@:2}"; do [[ "$e" = "$1" ]] && return 0; done; return 1; }
现在正确处理空数组。
这对我来说很管用:
# traditional system call return values-- used in an `if`, this will be true when returning 0. Very Odd.
contains () {
# odd syntax here for passing array parameters: http://stackoverflow.com/questions/8082947/how-to-pass-an-array-to-a-bash-function
local list=$1[@]
local elem=$2
# echo "list" ${!list}
# echo "elem" $elem
for i in "${!list}"
do
# echo "Checking to see if" "$i" "is the same as" "${elem}"
if [ "$i" == "${elem}" ] ; then
# echo "$i" "was the same as" "${elem}"
return 0
fi
done
# echo "Could not find element"
return 1
}
示例调用:
arr=("abc" "xyz" "123")
if contains arr "abcx"; then
echo "Yes"
else
echo "No"
fi
没有'grep'和循环的一行检查
if ( dlm=$'\x1F' ; IFS="$dlm" ; [[ "$dlm${array[*]}$dlm" == *"$dlm${item}$dlm"* ]] ) ; then
echo "array contains '$item'"
else
echo "array does not contain '$item'"
fi
这种方法既不使用grep这样的外部实用程序,也不使用循环。
这里发生的是:
we use a wildcard substring matcher to find our item in the array that is concatenated into a string; we cut off possible false positives by enclosing our search item between a pair of delimiters; we use a non-printable character as delimiter, to be on the safe side; we achieve our delimiter being used for array concatenation too by temporary replacement of the IFS variable value; we make this IFS value replacement temporary by evaluating our conditional expression in a sub-shell (inside a pair of parentheses)