What is the difference of running commands in terminal and shell script?

Question

I want to check if tmux alias exists, when I run command in terminal:

$ type -t tmux

the result is

$ alias

But when I put "type -t tmux" in a shell script and run, the result is

$ ./test.sh
$ file

Why the result is different ?

My test.sh is:

#!/usr/bin/env bash
set -e

type -t tmux

Answer 1

Any aliases defined in .bash_profile should be read and respected by tmux, but does not read anything in .bashrc .

Invoking test.sh is a sub-process, and does not use environment from current process unless you source it source test.sh but that also allows that script to modify current environment.