Curious, in case I'm missing something. Is what you've written equivalent to the following, or is there a reason for the pipe?

sort in.txt > out.txt

For those that don't know: there is/was an ancient meme called the "Useless Use of Cat Award" about that subject. See for instance http://en.wikipedia.org/wiki/Cat_(Unix)#Useless_use_of_cat, http://partmaps.org/era/unix/award.html, or http://unix.stackexchange.com/questions/16279/should-i-care-...

From the other comment, it is completely equivalent, and I will admit that the pipe is due purely to my ignorance. I usually use `sort` for sorting the output of other commands, and so I forget that it can open a file on its own.

That usage of cat is "wrong" in general:

    cat file | command > out

is the same as

    command < file > out

Don't worry about the cat it does have a purpose: portability. cat in.txt | sort > out.txt works in powershell(cat is an alias for Get-Content and sort is an alias for sort-object)(without the sort it wouln't work).

No need for cat!

    sort in.txt > out.txt

We are talking about a script, so it should be:

cat $1 | sort > $2