why cant ai use alias in my own script

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http://www.linuxquestions.org – I set Code: alias ll="ls -l" in ~/.bashrc but when I wrote my own script, I just can't use it anyway. Well, it turns out that the issue I met is about subshell etc. Then I tried to wrote Code: . ~/.bashrc and Code: alias ll="ls -l " , still, it doesn't work. It is too weird. I do still not clear about concept of shell, subshell, If /bin/bash is a shell, then I do really fell confused about difference between shell and program (HowTos)