I was wondering if there is an efficient way to check if an element is present within an array in Bash? I am looking for something similar to what I can do in Python, like:
arr = ['a','b','c','d']
if 'd' in arr:
do your thing
else:
do something
I've seen solutions using associative array for bash for Bash 4+, but I am wondering if there is another solution out there.
Please understand that I know the trivial solution is to iterate in the array, but I don't want that.
If array elements don't contain spaces, another (perhaps more readable) solution would be:
if echo ${arr[@]} | grep -q -w "d"; then
echo "is in array"
else
echo "is not in array"
fi
Obvious caveats aside, if your array was actually like the one above, you could do
if [[ ${arr[*]} =~ d ]]
then
do your thing
else
do something
fi
As bash does not have a built-in value in
array operator and the =~
operator or the [[ "${array[@]" == *"${item}"* ]]
notation keep confusing me, I usually combine grep
with a here-string:
colors=('black' 'blue' 'light green')
if grep -q 'black' <<< "${colors[@]}"
then
echo 'match'
fi
Beware however that this suffers from the same false positives issue as many of the other answers that occurs when the item to search for is fully contained, but is not equal to another item:
if grep -q 'green' <<< "${colors[@]}"
then
echo 'should not match, but does'
fi
If that is an issue for your use case, you probably won't get around looping over the array:
for color in "${colors[@]}"
do
if [ "${color}" = 'green' ]
then
echo "should not match and won't"
break
fi
done
for color in "${colors[@]}"
do
if [ "${color}" = 'light green' ]
then
echo 'match'
break
fi
done
Here's another way that might be faster, in terms of compute time, than iterating. Not sure. The idea is to convert the array to a string, truncate it, and get the size of the new array.
For example, to find the index of 'd':
arr=(a b c d)
temp=`echo ${arr[@]}`
temp=( ${temp%%d*} )
index=${#temp[@]}
You could turn this into a function like:
get-index() {
Item=$1
Array="$2[@]"
ArgArray=( ${!Array} )
NewArray=( ${!Array%%${Item}*} )
Index=${#NewArray[@]}
[[ ${#ArgArray[@]} == ${#NewArray[@]} ]] && echo -1 || echo $Index
}
You could then call:
get-index d arr
and it would echo back 3, which would be assignable with:
index=`get-index d arr`
array=("word" "two words") # let's look for "two words"
grep
and printf
:(printf '%s\n' "${array[@]}" | grep -x -q "two words") && <run_your_if_found_command_here>
for
:(for e in "${array[@]}"; do [[ "$e" == "two words" ]] && exit 0; done; exit 1) && <run_your_if_found_command_here>
For not_found results add || <run_your_if_notfound_command_here>
1) Initialize array arr
and add elements
2) set variable to search for SEARCH_STRING
3) check if your array contains element
arr=()
arr+=('a')
arr+=('b')
arr+=('c')
SEARCH_STRING='b'
if [[ " ${arr[*]} " == *"$SEARCH_STRING"* ]];
then
echo "YES, your arr contains $SEARCH_STRING"
else
echo "NO, your arr does not contain $SEARCH_STRING"
fi
FWIW, here's what I used:
expr "${arr[*]}" : ".*\<$item\>"
This works where there are no delimiters in any of the array items or in the search target. I didn't need to solve the general case for my applicaiton.
Source: Stackoverflow.com