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Difference between launching a script with ./script.sh and . ./script.sh

What is difference between running the script as ./script.sh and . ./script.sh

Answer 1

The built-in command . causes the script to be run in the current process rather than in a subprocess. Using . allows your script to alter the environment of the current process. For example:

$ echo $FOO

$ cat script.sh
#!/bin/bash export FOO="this is foo" 
$ ./script.sh 
$ echo $FOO

$ . ./script.sh 
$ echo $FOO 
this is foo

Notice how in the second case, the environment variable FOO was created in the current process.

Here’s a link to the bash man page section dealing with the . command:

http://www.gnu.org/software/bash/manual/bashref.html#index-g_t_002e-108