Parentheses ( ) create a new shell (subshell). Curly braces { } reuse the current shell.

 Think of it like this: Parentheses create a temporary "bubble" (clone), while Curly Braces are just a way to group instructions in the room you are already standing in.

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1. Parentheses ( ) - The Subshell

When you use ( ), the shell creates a child process (a subshell).

• Isolation: The subshell gets a copy of everything from the parent, but it cannot pass anything back.

• The "Vegas Rule": What happens in the subshell, stays in the subshell. If you change a variable inside ( ), it vanishes the moment the closing ) is reached.

Example:

name="Mahesh"
( 
  name="Ahana" 
  echo "Inside parens: $name" 
)
echo "Outside parens: $name"

Output:

Inside parens: Ahana
Outside parens: Mahesh   <-- The original variable was protected!

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2. Curly Braces { } - The Current Shell

When you use { }, you are simply grouping commands together in the current process.

• Integration: Everything happens in the "here and now."

• Permanent Changes: If you change a variable inside { }, it is changed for the rest of the script.

• Syntax Note: Braces require a ; (or newline) before the closing } and spaces after the opening {.

Example:

name="Mahesh"
{ 
  name="Ahana"
  echo "Inside braces: $name"
}
echo "Outside braces: $name"

Output:

Inside braces: Ahana
Outside braces: Ahana    <-- The original variable was overwritten!