How do create an alias in shell scripts? [duplicate]

Question

Definin an alias on Linux system is very simple.

From the following example we see that: the I_am_only_ls_alias alias command gives us the output as ls command

 # alias I_am_only_ls_alias=ls
 # I_am_only_ls_alias

Output:

file   file1

But when I trying to do the same in bash script (define alias I_am_only_ls_alias), I get I_am_only_ls_alias: command not found.

Example of my bash script:

alias_test.bash

#!/bin/bash

alias I_am_only_ls_alias=ls

I_am_only_ls_alias

Run the bash script - alias_test.bash

/tmp/alias_test.bash

Output:

/tmp/: line 88: I_am_only_ls_alias: command not found

So, first I want to ask:

Why doesn't bash recognize the command I_am_only_ls_alias as an alias?

And what do I need to do in order to define aliases inside a bash script? Is it possible?

Answer 1

From the bash man page:

Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt (see the description of shopt under SHELL BUILTIN COMMANDS below).

So this should work:

#!/bin/bash
shopt -s expand_aliases
alias I_am_only_ls_alias=ls
I_am_only_ls_alias

Scripts usually use functions, not aliases.