An alias defined in a bash script does not work within the same script [duplicate]

Question

I have a simple bash script.

alias myls=ls
myls

If I execute this script, I get an error.

$ bash foo.sh 
foo.sh: line 2: myls: command not found

• Why does the alias not work in the script?
• Does this behavior conform to POSIX?
• If it is indeed not supposed to work, could you please point me to an authoritative documentation that stays this?

Answer 1

See man bash:

Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt