By default variables are global in a shell script

#!/usr/bin/bash

sample()
{
  x=10
  echo "Enclosed under function the value of x is :$x"
}

sample
echo "Value of x outside the function is :$x"

myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$ ./scope.sh 
Enclosed under function the value of x is :10
Value of x outside the function is :10

In order to limit the scope of the variable to local then local keyword is used. local keyword can be only be used inside a function

#!/usr/bin/bash

sample()
{
  local x=10
  echo "Enclosed under function the value of x is :$x"
}

sample
echo "Value of x outside the function is :$x"

Output

myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$ ./scope.sh 
Enclosed under function the value of x is :10
Value of x outside the function is :
myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$ 

• local keyword used outside

#!/usr/bin/bash

sample()
{
  local x=10
  echo "Enclosed under function the value of x is :$x"
}

sample
local x=11
echo "Value of x outside the function is :$x"

Output

myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$ ./scope.sh 
Enclosed under function the value of x is :10
./scope.sh: line 10: local: can only be used in a function
Value of x outside the function is :
myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$ 

• Use return to access local variable

#!/usr/bin/bash

sample()
{
  local x=10
  echo $x
}

y=$(sample)
echo $y

Output

myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$ ./scope.sh 
10
myubuntu@myubuntu-VirtualBox:~/Desktop/shellScripts$