有点晚了，但你可以用这个:

#!/bin/bash
# isPicture.sh

FILE=$1
FNAME=$(basename "$FILE") # Filename, without directory
EXT="${FNAME##*.}" # Extension

FORMATS=(jpeg JPEG jpg JPG png PNG gif GIF svg SVG tiff TIFF)

NOEXT=( ${FORMATS[@]/$EXT} ) # Formats without the extension of the input file

# If it is a valid extension, then it should be removed from ${NOEXT},
#+making the lengths inequal.
if ! [ ${#NOEXT[@]} != ${#FORMATS[@]} ]; then
    echo "The extension '"$EXT"' is not a valid image extension."
    exit
fi

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)

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.

使用参数展开:

如果参数为空或未设置，则什么都没有 替换，否则词的展开就会被替换。

declare -A myarray
myarray[hello]="world"

for i in hello goodbye 123
do
  if [ ${myarray[$i]:+_} ]
  then
    echo ${!myarray[$i]} ${myarray[$i]} 
  else
    printf "there is no %s\n" $i
  fi
done

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 $*

containsElement () { for e in "${@:2}"; do [[ "$e" = "$1" ]] && return 0; done; return 1; }

现在正确处理空数组。