Alias is a very useful feature of shell (e.g. bash). For example, I have this line in my .bashrc:

alias ll="ls -alF | more"

So I can simply use ll to view all the files in current directory and view them in my favorite style.

It works fine until one day, I want to view the files in a sub directory instead of current directory, so I tried:

$ ll subdirectory/

But it failed - still just display the content of current directory. The reason is, for bash, the above command is interpreted as:

$ ls -alF | more subdirectory/

But what I have in mind is actually:

$ ls -alF subdirectory | more

I Googled and found that alias can just not take arguments, but devise a simple functions is applicable, so I have the below code instead of the ll alias:

unalias ll
function ll(){
    ls -alF "$@" | more;

We need to first unalias since by default, ll is aliased as ls -l --color=auto. If we don't remove the alias, our function won't be invoked.