Question

In a shell, what is the difference between?

. executable

and

./executable

In the first one, the dot a shortcut for source right? So is there a difference between ./executable and source executable?

Answer 1

is there a difference between ./executable and source executable?

basic difference is,

./foo.sh      - foo.sh will be executed in a sub-shell
source foo.sh - foo.sh will be executed in current shell

some example could help to explain the difference:

let’s say we have foo.sh:

#!/bin/bash
VAR=100

source it:

$ source foo.sh 
$ echo $VAR
100

if you :

./foo.sh
$ echo $VAR
[empty]

another example, bar.sh

#!/bin/bash
echo "hello!"
exit 0

if you execute it like:

$ ./bar.sh
hello
$

but if you source it:

$ source bar.sh
<your terminal exits, because it was executed with current shell>