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Summary
| Syntax |
Result |
arr=() |
Create an empty array |
arr=(1 2 3) |
Initialize array |
${arr[2]} |
Retrieve third element |
${arr[@]} |
Retrieve all elements |
${!arr[@]} |
Retrieve array indices |
${#arr[@]} |
Calculate array size |
arr[0]=3 |
Overwrite 1st element |
arr+=(4) |
Append value(s) |
str=$(ls) |
Save ls output as a string |
arr=( $(ls) ) |
Save ls output as an array of files |
${arr[@]:s:n} |
Retrieve n elements starting at index s |
| S/N |
Action |
Example(s) |
| 1 |
Declare |
# indexed array
declare -a myarray1
declare -a myarray2=()
declare -a myarray3=(abc def ghi)
declare -a myarray4=('abc' 'def' 'ghi')
# Associative array
declare -A myhash
declare -A myhash=([1]="string1" [2]="string2" [4]="string4")
|
| 2 |
Display |
declare -a myarray=(a b c d e f g h i j k)
# DISPLAY ALL ELEMENTS OF AN ARRAY
echo ${myarray[@]}
a b c d e f g h i j k
# DISPLAY SPECIFIC LEMENTS OF AN ARRAY E.G. INDEX 0
echo ${myarray[0]}
a
# DISPLAY SPECIFIC ELEMENTS OF 2 DIMENTION ARRAY E.G. INDEX 0,0
echo ${matrix[0,0]}
# DISPLAY A RANGE OF ELEMENTS STARTING AT INDEX 1 ENDING AT 3
echo ${myarray[@]:1:3}
b c d
# Fetching values from associative arrays
echo ${arr[my key]}
echo ${arr["my key"]}
echo ${arr[$my_key]}
|
| 3 |
Assign |
# assign one element in indexed array
declare -a myarray
myarray[0]=A
# Assigning values to associative arrays
arr[my key]="my value"
arr["my key"]="my value"
arr[$my_key]="my value"
|
| 4 |
Count |
# GET THE LENGTH OF THE ARRAY
echo ${#myarray[@]}
# COUNT CHARACTERS IN ONE ELEMENT OF THE ARRAY
echo ${#myarray[0]}
|
| 5 |
Iterate |
# INDEXED ARRAY - iterate by the elements
declare -a myarray=(a b c d)
for e in "${myarray[@]}"
do
echo $e
done
# INDEXED ARRAY - iterate by the indices
declare -a myarray=(a b c d)
for ((i=0;i<${#myarray[@]};i++));
do
printf "%d : %s\n" $i ${myarray[$i]};
done;
# ASSOCIATIVE ARRAY
for k in "${!array[@]}"
do
printf "%s\n" "$k=${array[$k]}"
done
|
| |
Copy |
# COPY AN ARRAY TO ANOTHER VARIABLE
declare -a original=("a" "b" "c" "d")
copy=(${original[*]})
for e in "${original[@]}";do echo $e;done;
a
b
c
d
for e in "${copy[@]}";do echo $e;done;
a
b
c
d |
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References:: https://www.thegeekstuff.com/2010/06/bash-array-tutorial/
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