Detailed explanation of the usage of Linux Shell Map

Map definition:

When using map, you need to declare it first, otherwise the result may be different from expected. Array can not be declared

Method 1:

declare -A myMap
myMap["my03"]="03"

Method 2:

declare -A myMap=(["my01"]="01" ["my02"]="02")
myMap["my03"]="03"
myMap["my04"]="04"

Map initialization:

Similar to array, you can use brackets to initialize directly, or you can initialize data by adding them. Unlike array, when brackets are directly initialized, they are used as a key-value pair. When adding elements, the subscript may not be an integer.

myMap["my03"]="03"
myMap["my04"]="04"

Output all keys, value, and lengths of Map:

#1) Output all keys#If the map is not declared using declare, then 0 will be output here, which does not match the expected output. There is one more output statement format than arr!echo ${!myMap[@]}
#2) Output all values#The same format as array outputecho ${myMap[@]}
#3) Output map length#The same format as array outputecho ${#myMap[@]}

Map traversal:

#1)Travel and find the corresponding value according to the keyfor key in ${!myMap[*]};do
 echo $key
 echo ${myMap[$key]}
done
#2) Iterate through all keysfor key in ${!myMap[@]};do
 echo $key
 echo ${myMap[$key]}
done
#3)Transfer all valuesfor val in ${myMap[@]};do
 echo $val
done

Map test:

[root@cdh-143 shell-test]# more 
#!/bin/sh

echo "one、definitionMap:declare -A myMap=([\"myMap00\"]=\"00\" [\"myMap01\"]=\"01\")"
declare -A myMap=(["my00"]="00" ["my01"]="01")
myMap["my02"]="02"
myMap["my03"]="03"

echo "2. Output all keys:"
echo ${!myMap[@]}

echo "Three, output all values:"
echo ${myMap[@]}

echo "IV. The length of the output map:"
echo ${#myMap[@]}

echo "Five. Traversal, find the corresponding value according to the key:"
for key in ${!myMap[*]};do
 echo "key:"$key
 echo "value:"${myMap[$key]}
done

echo "Six. Go through all keys:"
for key in ${!myMap[@]};do
 echo "key:"$key
 echo "value:"${myMap[$key]}
done

echo "7. Go through all values:"
for val in ${myMap[@]};do
 echo "value:"$val
done

Output:

[root@cdh-143 shell-test]# ./
1. Define Map:declare -A myMap=(["myMap00"]="00" ["myMap01"]="01")
2. Output all keys:
my02 my03 my00 my01
3. Output all values:
02 03 00 01
4. The length of the output map:
4
5. Traversal and find the corresponding value according to the key:
key:my02
value:02
key:my03
value:03
key:my00
value:00
key:my01
value:01
6. Go through all keys:
key:my02
value:02
key:my03
value:03
key:my00
value:00
key:my01
value:01
7. Go through all values:
value:02
value:03
value:00
value:01
[root@cdh-143 shell-test]#

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