UNIX for Dummies Questions & Answers

Hi,

I know this question has been asked before, but I'd like to ask for some explanation rather than solution regarding finding median in unix.
I've got a simple one column file with over 2 million numbers and I need to find its median. The file looks like this:
0.123
0.235
0.890
0.000 etc (just plain numbers).

The solution that I've found in forum answers was:
1) find the number of lines with this code:

wc -l filename

In my case it is: 2543887

2) if the number is not even (like in my case) than the median can be found with this code:

cat filename| head -$2543887 | tail -1

My question is how head -2543887 is different to head -$2543887? What does the dollar sign do?

Many thanks in advance!

Code:

cat filename| head -$2543887 | tail -1

Is it a correct command? Did you try this?? and cant see any maths here to get the median. am confused.

Yes, I've tried it and the answer was 0.0751, while typing just
cat filename | head -$254887 | tail -1 gives 9.9997. So, these two command lines do something different?

I'm new to Unix. Do you think what I found won't give me the median? What do you think I should use?

Many thanks!

---------- Post updated at 07:59 AM ---------- Previous update was at 07:56 AM ----------

sorry, I meant that typing
cat filename | head -2543887 |tail -1 gives 9.9997
So, typing it with or without the dollar sign gives different outputs...

i did not knew this $ thing with head...
and for median, i think you need to do the statistcs part. I dont know the formula

I don't follow, how the head|tail can calculate the median.

Unofrtunately, I'm new to Unix and don't know how the head and tail can calculate the median, but I thought that the dollar sign is a trick. This is why I asked the question in the first place.
Does anyone know how to calculate the mean, then?

---------- Post updated at 08:14 AM ---------- Previous update was at 08:10 AM ----------

sorry, I meant how to calculate the median

Google is your friend