Bashscripts.org

I decided it was time to learn, or improve some basic scripting skills. I came up with a little project to work on for practice.
I would appreciate any advice. The script follows, then some output, and finally my questions.

The project is to write a script that flips a coin X number. The number of times heads or tails occurs in a row should be recorded. Those results should graphable or converted to a format which could be graphed (like CVS) By the way I don't have the slightest idea how to do this last part. But this is what we have so far.

This flips the coin and records the result

#!/bin/bash
#
# The plan is to write a shell scripts that flips a coin X times
# and records how many times head or tails
# occur in a row. And then perhaps to graph the out put
#
# create some files and setup some variable
touch coinflips
> coinflips
COUNTER=$1
tails=0
heads=0
# generate random number as many times as specified on command line.
# Then just take the last digit
until [ $COUNTER -lt 0 ]; do
for NUMROLL in `echo $RANDOM | sed -e "s/^.*\(.\)$/\1/"`
do
if [ $((NUMROLL % 2)) -eq 0 ]; then
# if it is even then add 1 to the count of variable heads
tails=0
heads=$((heads+1))
echo "Heads are $heads in a row" >> coinflips
else
# otherwise add 1 to tails
heads=0
tails=$((tails+1))
echo "Tails are $tails in a row">> coinflips
fi
let COUNTER-=1
done
done
------------------------------------------------------------------------
example output
tom@lugh:~/scripts$ ./rollit 10
tom@lugh:~/scripts$ cat coinflips
Tails are 1 in a row
Heads are 1 in a row
Tails are 1 in a row
Tails are 2 in a row
Tails are 3 in a row
Heads are 1 in a row
Tails are 1 in a row
Tails are 2 in a row
Heads are 1 in a row
Heads are 2 in a row
Tails are 1 in a row
--------------------------------------------------------------
Questions:

1. It should really only record the highest number of times heads or tails occured for each toss. For example in the output where it says Tails 1 then tails 2 then tails 3; only the tails 3 should exist. Leaving the others could be statistically misleading in our graph. I am not sure what I am doing wrong there.

2. Is there anything I am doing that could be done more efficiently or more correctly.

3. There anyway to do graphing in bash. Theoretically this should just create a perfect gausian curve. This must be possible as I have seen old time ascii art. Perhaps a lost art.

4. There seem to be 11 flips not 10 as $1 requested, Why?

5 If anyone wants to recommend any other learning projects please feel free.

Thanks for any advice. And sorry if this is the wrong place to post

Hi! This is a neat brush-up project

Here's what I would do to fix #1 -> You'll want to keep track of what the LAST flip was, and compare it with the CURRENT flip. Try adding a "LAST" variable to the mix, and checking to see if the current flip is the same as the last one before printing the "in a row" message.

For # 2, there's ALWAYS room to make things more efficient! As for 'correct'... I'm no expert... For instance, instead of using 'touch' to create the coinflip file, you *should* be able to simply use the '> coinfile' line to create the file if it doesn't exist or clear it if it does. Or you could make it more readable with something like "echo -n > coinflips".

You also might consider defining the output file in a variable, in case you want to use a different file later, you can change it in one place instead of three.

#3 Not sure! This would be interesting to investigate. I mean, you might be able to use something like MRTG or RRDTool, but I'm sure there's something simpler...

#4 Take a closer look at your 'until' loop. It might be obvious if you do the math on how many iterations you're asking for there

I hope this helps!
-J