What is the correct first line when I create bash script?
As I suppose that you are asking about first line of the script.
sh as substitutes but they are not the same.
Writing script it is necessary to set first line to indicates script 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:
Using Bash shell first line should be:
bashis like improvement for
Do not forget to add permissions to execute your script:
chmod u+x my_script.sh