Linux bash correct first line header

As I suppose that you are asking about first line of the script.

People uses bash and sh as substitutes but they are not the same.

Writing script it is necessary to set first line to indicates script interpreter.

#!/path/to/interpreter

Depending what interpreter you whould like to use we can select Bourne shell, Bash shell or something other (python, php, perl, lua, ...).

Using Bourne shell first line should be:

#!/bin/sh

Using Bash shell first line should be:

#!/bin/bash

Summary: bash is like improvement for sh.

Do not forget to add permissions to execute your script:

chmod u+x my_script.sh

See also:

1. Bash correct header #!/bin/sh - create simple bin sh shell script with .sh code example

Resources

1. https://en.wikipedia.org/wiki/Bash_(Unix_shell)
2. https://en.wikipedia.org/wiki/Bourne_shell