Bash Variable

Bash Variable in bash shell scripting is a memory location that is used to contain a number, a character, a string, an array of strings, etc.

Some important points to remember about variables in bash scripting

  • There are no data types for a variable. It can contain a number, a character, a string, an array of strings, etc. and be overridden with any other value.
  • There is no need to declare a variable explicitly. When you assign a value to the reference, variable declaration happens implicitly.

We shall go through the following topics in this tutorial

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Syntax

Following is the syntax to initialize a variable

variableReference=value

Note : No space should be given before and after = , failing which produces error “syntax error near unexpected token“.

Examples for Bash Variable

Following example demonstrates simple initialization of bash variables of types : number, character, string and array.

Bash Script File

#!/bin/bash

# number variable
num=10
echo $num

# character variable
ch='c'
echo $ch

# string variable
str="Hello Bob!"
echo $str

# array variable
arr=( "bash" "shell" "script" )
echo "${arr[0]}"
echo "${arr[1]}"
echo "${arr[2]}"

When the above bash variable example is run in Terminal, we will get the following output.

Output

$ ./bash-variable-example 
10
c
Hello Bob!
bash
shell
script

Bash Local Variable

Bash Local Variable is used to override a global bash variable, in local scope, if already present with the same name.

Syntax

Following is the syntax of a bash local variable

local variableReference=value

Example

Following is an example bash script to demonstrate the usage of local variable.

Bash Script File

#!/bin/bash

# bash variable
SHELL="Unix"

function bashShell {
	# bash local variable
	local SHELL="Bash"
	echo $SHELL
}

echo $SHELL
bashShell
echo $SHELL

When above bash local variable example is run in Terminal, we will get the following output.

Output

arjun@arjun-VPCEH26EN:~/workspace/bash$ ./bash-local-variable-example 
Unix
Bash
Unix

The first echo statement is in global scope andSHELL  has value of UNIX, but whenbashShell  function is called, the local variableSHELL  overrides the global variable and hence theecho $SHELL  echoed Bash.

Conclusion

In this Bash Tutorial – Bash Variable, we have learnt that there are no data types in bash, and the syntax to initialize a variable, and also about local bash local variables with example scripts.