Why to use bash in executing script?

Question

In a former question, I was suggested to execute:

sudo bash start-dfs.sh

why not

sudo start-dfs.sh

? I mean, what difference does bash makes?

Answer 1

A script in any (interpreted) language, like bash or python, needs to be "interpreted" by the interpreter of the corresponding language.

On Linux, this can be done in different ways:

1. The interpreter is "asked" to run the script by including the language in the command to run the script:

   <language> <script>
   

   or in your example:

   sudo bash start-dfs.sh
   

2. The script is executable, and has the permission to "ask" the interpreter itself to run the code inside the script. from your example:

   sudo start-dfs.sh
   

   In this case, the script must start with the shebang, else there is no information what interpreter to call, like:

   #!/bin/bash
   

   or:

   #!/usr/bin/env python
   

Notes

• In case the first option is used, the language information in the command always overrules a possible shebang, no matter if the script is executble or not.
• The extension on a script (.sh, .py etc) makes clear what type of script it is, but plays no role whatsoever in the execution of a script, unlike in windows.