How do I create an array in unix shell scripting?
114 Answers
The following code creates and prints an array of strings in shell:
#!/bin/bash array=("A" "B" "ElementC" "ElementE") for element in "${array[@]}" do echo "$element" done echo echo "Number of elements: ${#array[@]}" echo echo "${array[@]}" Result:
A B ElementC ElementE Number of elements: 4 A B ElementC ElementE in bash, you create array like this
arr=(one two three) to call the elements
$ echo "${arr[0]}" one $ echo "${arr[2]}" three to ask for user input, you can use read
read -p "Enter your choice: " choice Bourne shell doesn't support arrays. However, there are two ways to handle the issue.
Use positional shell parameters $1, $2, etc.:
$ set one two three $ echo $* one two three $ echo $# 3 $ echo $2 two Use variable evaluations:
$ n=1 ; eval a$n="one" $ n=2 ; eval a$n="two" $ n=3 ; eval a$n="three" $ n=2 $ eval echo \$a$n two #!/bin/bash # define a array, space to separate every item foo=(foo1 foo2) # access echo "${foo[1]}" # add or changes foo[0]=bar foo[2]=cat foo[1000]=also_OK You can read the ABS "Advanced Bash-Scripting Guide"
2The Bourne shell and C shell don't have arrays, IIRC.
In addition to what others have said, in Bash you can get the number of elements in an array as follows:
elements=${#arrayname[@]} and do slice-style operations:
arrayname=(apple banana cherry) echo ${arrayname[@]:1} # yields "banana cherry" echo ${arrayname[@]: -1} # yields "cherry" echo ${arrayname[${#arrayname[@]}-1]} # yields "cherry" echo ${arrayname[@]:0:2} # yields "apple banana" echo ${arrayname[@]:1:1} # yields "banana" Try this :
echo "Find the Largest Number and Smallest Number of a given number" echo "---------------------------------------------------------------------------------" echo "Enter the number" read n i=0 while [ $n -gt 0 ] #For Seperating digits and Stored into array "x" do x[$i]=`expr $n % 10` n=`expr $n / 10` i=`expr $i + 1` done echo "Array values ${x[@]}" # For displaying array elements len=${#x[*]} # it returns the array length for (( i=0; i<len; i++ )) # For Sorting array elements using Bubble sort do for (( j=i+1; j<len; j++ )) do if [ `echo "${x[$i]} > ${x[$j]}"|bc` ] then t=${x[$i]} t=${x[$i]} x[$i]=${x[$j]} x[$j]=$t fi done done echo "Array values ${x[*]}" # Displaying of Sorted Array for (( i=len-1; i>=0; i-- )) # Form largest number do a=`echo $a \* 10 + ${x[$i]}|bc` done echo "Largest Number is : $a" l=$a #Largest number s=0 while [ $a -gt 0 ] # Reversing of number, We get Smallest number do r=`expr $a % 10` s=`echo "$s * 10 + $r"|bc` a=`expr $a / 10` done echo "Smallest Number is : $s" #Smallest Number echo "Difference between Largest number and Smallest number" echo "==========================================" Diff=`expr $l - $s` echo "Result is : $Diff" echo "If you try it, We can get it" Your question asks about "unix shell scripting", but is tagged bash. Those are two different answers.
The POSIX specification for shells does not have anything to say about arrays, as the original Bourne shell did not support them. Even today, on FreeBSD, Ubuntu Linux, and many other systems, /bin/sh does not have array support. So if you want your script to work in different Bourne-compatible shells, you shouldn't use them. Alternatively, if you are assuming a specific shell, then be sure to put its full name in the shebang line, e.g. #!/usr/bin/env bash.
If you are using bash or zsh, or a modern version of ksh, you can create an array like this:
myArray=(first "second element" 3rd) and access elements like this
$ echo "${myArray[1]}" # for bash/ksh; for zsh, echo $myArray[2] second element You can get all the elements via "${myArray[@]}". You can use the slice notation ${array[@]:start:length} to restrict the portion of the array referenced, e.g. "${myArray[@]:1}" to leave off the first element.
The length of the array is ${#myArray[@]}. You can get a new array containing all the indexes from an existing array with "${!myArray[@]}".
Older versions of ksh before ksh93 also had arrays, but not the parenthesis-based notation, nor did they support slicing. You could create an array like this, though:
set -A myArray -- first "second element" 3rd You can try of the following type :
#!/bin/bash declare -a arr i=0 j=0 for dir in $(find /home/rmajeti/programs -type d) do arr[i]=$dir i=$((i+1)) done while [ $j -lt $i ] do echo ${arr[$j]} j=$((j+1)) done An array can be loaded in twoways.
set -A TEST_ARRAY alpha beta gamma or
X=0 # Initialize counter to zero. -- Load the array with the strings alpha, beta, and gamma
for ELEMENT in alpha gamma beta do TEST_ARRAY[$X]=$ELEMENT ((X = X + 1)) done Also, I think below information may help:
The shell supports one-dimensional arrays. The maximum number of array elements is 1,024. When an array is defined, it is automatically dimensioned to 1,024 elements. A one-dimensional array contains a sequence of array elements, which are like the boxcars connected together on a train track.
In case you want to access the array:
echo ${MY_ARRAY[2] # Show the third array element gamma echo ${MY_ARRAY[*] # Show all array elements - alpha beta gamma echo ${MY_ARRAY[@] # Show all array elements - alpha beta gamma echo ${#MY_ARRAY[*]} # Show the total number of array elements - 3 echo ${#MY_ARRAY[@]} # Show the total number of array elements - 3 echo ${MY_ARRAY} # Show array element 0 (the first element) - alpha If you want a key value store with support for spaces use the -A parameter:
declare -A programCollection programCollection["xwininfo"]="to aquire information about the target window." for program in ${!programCollection[@]} do echo "The program ${program} is used ${programCollection[${program}]}" done "Associative arrays are created using declare -A name. "
There are multiple ways to create an array in shell.
ARR[0]="ABC" ARR[1]="BCD" echo ${ARR[*]} ${ARR[*]} prints all elements in the array.
Second way is:
ARR=("A" "B" "C" "D" 5 7 "J") echo ${#ARR[@]} echo ${ARR[0]} ${#ARR[@]} is used to count length of the array.
To read the values from keybord and insert element into array
# enter 0 when exit the insert element echo "Enter the numbers" read n while [ $n -ne 0 ] do x[$i]=`expr $n` read n let i++ done #display the all array elements echo "Array values ${x[@]}" echo "Array values ${x[*]}" # To find the array length length=${#x[*]} echo $length A Simple way :
arr=("sharlock" "bomkesh" "feluda" ) ##declare array len=${#arr[*]} #determine length of array # iterate with for loop for (( i=0; i<len; i++ )) do echo ${arr[$i]} done In ksh you do it:
set -A array element1 element2 elementn # view the first element echo ${array[0]} # Amount elements (You have to substitute 1) echo ${#array[*]} # show last element echo ${array[ $(( ${#array[*]} - 1 )) ]} 
