Defining Array Values in Unix // Linux: Use Array in Shell

A shell variable is able to hold a single value. This type of variables is called scalar variables.

The shell supports different types of variables called an array variable that can hold multiple values at the same time. Arrays provide a method for grouping a set of variables. Instead of creating a new name for each required variable, you can use an array variable to store all other variables.

All name rules are discussed in chapter Shell variables that will be applied during array naming.

Define array values in Unix / Linux

The difference between an array variable and a scalar variable can be explained as follows:

When you are trying to represent the names of different students as a set of variables. Each single variable is a scalar variable as follows:

 NAME01 = "Zara" NAME02 = "Qadir" NAME03 = "Mahnaz" NAME04 = "Ayan" NAME05 = "Daisy" 

We use a single array to keep all the names mentioned above. The following is a simple method for creating an array variable to assign a value to one of them. This is described as follows:

 array_name [ index ] = value 

Here array_name is the name of the array, index is the index of the items in the array you want to set and value is the value you want to set for that item.

Here is an example, the following commands:

 NAME [ 0 ] = "Zara" NAME [ 1 ] = "Qadir" NAME [ 2 ] = "Mahnaz" NAME [ 3 ] = "Ayan" NAME [ 4 ] = "Daisy" 

If you are using ksh shell, then the syntax of the array is:

 set - A array_name value1 value2 . valuen 

If you are using a bash shell, here the array syntax is:

 array_name = ( value1 . valuen ) 

Access to array values in Unix / Linux

After you have set any array value, you can access it as follows:

Here array_name is the array name, and index is the index of the values to be accessed. Here is a simple example:

 #! / bin / sh NAME [ 0 ] = "Zara" NAME [ 1 ] = "Qadir" NAME [ 2 ] = "Mahnaz" NAME [ 3 ] = "Ayan" NAME [ 4 ] = "Daisy" echo "First Index : " echo " Second Index: " 

It will produce the following result:

 $ ./ test . sh First Index : Zara Second Index : Qadir 

You can access all items in an array in one of the following ways:

 $ { array_name [*]} $ { array_name [@]} 

Here array_name is the name of the array you are interested in. Here is a simple example:

 #! / bin / sh NAME [ 0 ] = "Zara" NAME [ 1 ] = "Qadir" NAME [ 2 ] = "Mahnaz" NAME [ 3 ] = "Ayan" NAME [ 4 ] = "Daisy" echo "First Method : $ {NAME [*]} " 

Next lesson: Basic Shell operators