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
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[*]} " =~ " ${value} " ]] && echo "true" || echo "false"
其他回答
没有'grep'和循环的一行检查
if ( dlm=$'\x1F' ; IFS="$dlm" ; [[ "$dlm${array[*]}$dlm" == *"$dlm${item}$dlm"* ]] ) ; then
echo "array contains '$item'"
else
echo "array does not contain '$item'"
fi
这种方法既不使用grep这样的外部实用程序,也不使用循环。
这里发生的是:
we use a wildcard substring matcher to find our item in the array that is concatenated into a string; we cut off possible false positives by enclosing our search item between a pair of delimiters; we use a non-printable character as delimiter, to be on the safe side; we achieve our delimiter being used for array concatenation too by temporary replacement of the IFS variable value; we make this IFS value replacement temporary by evaluating our conditional expression in a sub-shell (inside a pair of parentheses)
我有这样的情况,我必须检查一个ID是否包含在另一个脚本/命令生成的ID列表中。 我的工作如下:
# the ID I was looking for
ID=1
# somehow generated list of IDs
LIST=$( <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…
别胡闹了!使您的解决方案简单、干净和可重用。
这些函数负责索引数组和关联数组。可以通过将搜索算法从线性搜索升级为二进制搜索(用于大型数据集)来改进它们。
##
# Determines if a value exists in an array.
###
function hasArrayValue ()
{
local -r needle="{$1:?}"
local -nr haystack="{$2:?}" # Where you pass by reference to get the entire array in one argument.
# Linear search. Upgrade to binary search for large datasets.
for value in "${haystack[@]}"; do
if [[ "$value" == "$needle" ]]; then
return 0
fi
done
return 1
}
##
# Determines if a value exists in an associative array / map.
###
function hasMapValue ()
{
local -r needle="{$1:?}"
local -nr haystack="{$2:?}"
# Linear search. Upgrade to binary search for large datasets.
for value in "${haystack[@]}"; do
if [[ $value == $needle ]]; then
return 0
fi
done
return 1
}
是的,同样的逻辑,但在处理bash时,如果函数的名称可以让您知道迭代的对象(或不迭代的对象),则可能(可能)有用。
for i in "${array[@]}"
do
if [ "$i" -eq "$yourValue" ] ; then
echo "Found"
fi
done
字符串:
for i in "${array[@]}"
do
if [ "$i" == "$yourValue" ] ; then
echo "Found"
fi
done
另一个没有函数的代码:
(for e in "${array[@]}"; do [[ "$e" == "searched_item" ]] && exit 0; done) && echo "found" || echo "not found"
谢谢@Qwerty关于空格的提示!
对应的功能:
find_in_array() {
local word=$1
shift
for e in "$@"; do [[ "$e" == "$word" ]] && return 0; done
return 1
}
例子:
some_words=( these are some words )
find_in_array word "${some_words[@]}" || echo "expected missing! since words != word"