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KSH For Loop Array: Iterate Through Array Values

How do I use ksh for loop to iterate thought array values under a UNIX / Linux / BSD operating systems?

The ksh shell supports two types of arrays:

  1. Indexed array
  2. associative array

Tutorial details
DifficultyEasy (rss)
Root privilegesNo
RequirementsKsh
Estimated completion time5m
An element of a ksh array variable is referenced by a subscript. The value of all non-negative subscripts must be in the range of 0 through 4,194,303.

Syntax

You can define array as follows either as an associative array or to be an indexed array.

Syntax for an indexed array

arrayName[0]=value1
arrayName[1]=value2
arrayName[3]=value3

OR use set command as follows:

set -A arrayName value1 value2 value3

Syntax for an associative array

typeset -A employees
employees[sirname]="value1"
employees[firstname]="value"

OR

set -A arrayName val1 val2 val3

Examples for ksh indexed array

For example, create an array called characters with three values as follows:

set -A characters Mugen Jin Fuu

To print first value, enter:

echo ${characters[0]}

To print 3rd and last value, enter:

echo ${characters[2]}

To print all values, enter:

echo ${characters[@]}

To count number of items in an array called characters, enter:

echo ${#characters[@]}

You can use for loop as follows to iterate through all values:

for i in ${characters[@]}; do echo "Samurai Champloo character - $i"; done

Sample outputs:

Samurai Champloo character - Mugen
Samurai Champloo character - Jin
Samurai Champloo character - Fuu

You can add two more items as follows to exiting array:

characters[3]="Sunflower-Samurai"
characters[4]="Detective-Manzo"

Sample Shell Script

#!/bin/ksh
# set array called nameservers
set -A nameservers 192.168.1.1 192.168.1.5 202.54.1.5
 
# print all name servers
for i in ${nameservers[@]}
do
	echo $i
done
 

Sample outputs:

Fig.01: Ksh for loop array ns demo

Fig.01: Ksh for loop array ns demo

Ksh associative arrays examples

## set associative array ##
typeset -A ns
 
## Add values ##
ns[home]="192.168.1.254" ## home dns server ip 
ns[isp]="123.1.2.254"    ## my isp dns server ip
ns[google]="8.8.8.8"     ## google public dns server ip
 
## Okay, display values #
print "${ns[home]}"
print "${ns[isp]}"
print "${ns[google]}"
 
## Count  number of items in an array #
print "${!ns[@]}"
 
## Use for loop to print all items in an array##
for i in "${!ns[@]}"
do
   echo "ns[$i] value is ${ns[$i]}"
done
 

Sample outputs:

ns[google] value is 8.8.8.8
ns[home] value is 192.168.1.254
ns[isp] value is 123.1.2.254
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{ 5 comments… add one }

  • Nisrine August 19, 2011, 7:05 am

    If i need to print the next value in the array if a certain condition is verified
    for example:
    for i in “${array[@]}”
    do
    if(….) then
    echo $(i+1)
    fi
    done

    $(i+1) is wrong what can i do?

    • Jason October 16, 2012, 12:26 pm

      Hi Nisrine,

      I hope my necromancing is welcome here, in case your issue is still relevant.

      $(ì+1) should actually be $((i+1)), since double parentheses evaluate mathematical expressions.

      I hope this helps someone!

      Jason

      • Nisrine October 16, 2012, 2:14 pm

        Thank you for ur reply! working!

        • rishab July 21, 2015, 12:31 pm

          Wow she actually used your solution after 1 year :-P

  • Ken June 18, 2012, 9:21 pm

    Excellent just what i needed for looping through an array

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