### Archive

Posts Tagged ‘linux’

## My first try creating a bash script

I am a ubuntu user, but sometimes I also use windows, mainly because my computer in the office is using windows. So, I use both ubuntu and windows. Even, my laptop has both windows and ubuntu. I tried to get rid of windows once, and installed wine to use windows application in my ubuntu. But it runs very slowly and it’s killing me and in the end, I came back to reinstall windows. I mainly use ubuntu for my research. The softwares I use for my research are auto, python, dstool, latex, xfig which run smoothly in ubuntu, even though python and latex can also be installed and run smoothly on windows machine. On the other hand, I use windows to do some regular activities such as browsing the internet, watching movies, checking my email, creating an office documents etc. All of which can be done in ubuntu as well. But there are activities that I must use windows, I sometimes need to use matlab and sometimes I like to play a game that only runs in windows. These two things are the main reason I still come back to use windows. Recently, I learn python so I am now trying to less use matlab.

That is just a background and my main point here is about bash scripting. After a few years using ubuntu, I have not created any bash script. Today, finally I learn to create one script. I created a script to automate my boring routine. When I write a paper, I need some illustrations. I mostly use xfig to create some mathematical images and to be able to use $\LaTeX$ in the figure I need to convert it to an eps file. The produced eps file will be then converted to a pdf file as it is perfectly compatible to my pdflatex command. But before that, I need to crop the resulted pdf file in order to remove white space around the image. Suppose the name of my xfig file is spam.fig. I then write a series of command.

```figtex2eps spam.fig
ps2pdf spam.eps
pdfcrop spam.pdf
```

I want to write a script that do all the above automatically. Thus I created the following script.

```#!/bin/bash
# Converts a .fig-file (xfig file) to a .eps-file by using a built-in function figtex2eps
# and then convert it to a .pdf file by using a built-in function ps2pdf
# and finally convert it to a cropped pdf file by using a built-in function pdfcrop
#
# ivanky saputra https://ivanky.wordpress.com
#
# credit to :
# \$ /home/abel/c/berland/etc/cvsrepository/figtex2eps/prog/figtex2eps \$
# \$ ps2pdf in ubuntu \$
# \$ pdfcrop in ubuntu \$
echo "We are going to change the following \$1.fig to a cropped pdf file"
function quit {
exit
}
if [\$1 == ""];
then
echo "no files given";
quit
else
echo "Processing \$1.fig............";
figtex2eps \$1.fig
ps2pdf \$1.eps
pdfcrop \$1.pdf
echo "Done";
fi
```

As someone has said that it is better to share your code and data openly as we as human are idiots and will make mistakes, please give me any suggestion to improve mine.

## My first Coursera course

In the middle of this year, I received a Fulbright Visiting Scholar that allowed me to go to Athens, OH, US. I spent four months in Ohio University starting in September, which means that I took a leave in the university I am working. One of my activities while I was in Ohio University was I took a course from Coursera. At that time I was eager to learn and to know python programming language therefore I decided to take the course, An Introduction to Interactive Programming in Python, offered by Rice University taught by the following professors: Joe Warren, Scott Rixner, John Griener, and Stephen Wong.

My first coursera was nothing but really, really good. The class could not definitely be better. The intructors have put so much effort in preparing the class and at the same time they were really enjoyable and fun. I really learned a lot from this class and I recommend everyone to take this class. After nine weeks, I finished the course and proudly said that I got 96.9% with distinction mark.

But what I wanted to tell here is the content of the course. From knowing nothing of Python I now know that the word ‘python’ is originally from the Month Python’s Flying Circus not the reptilia. I also know how useful this new programming language is. Python can be used to build an interactive game, to conduct some scientific computations, to analyse data science and many more. There are already many communities that use Python and they are (still) growing. One more good thing is the fact that it is free. Python works on either Windows, Linux or Mac and the installation on each device is not that difficult. I am using both Windows and Ubuntu. For Windows, I use mainly Python(x,y) and for Ubuntu, I don’t have to do anything as it is already inside. However, in this course, I did not have to use all of these as one of the instructors has built a nice Python web application that is called Codeskulptor. It will allows us to make a python scripts on your web browser so actually you don’t have to install python in your computer.

From the course, I learned to make interactive games. Even though the games I made were not perfect but I think it is playable and fun enough. I learned to make games like rock-paper-scissors-spock-lizzard, number guessing game, stopwatch game, pong, memory, and asteroids. The following links are the python scripts for all of the above games I made during the course. The link will bring you to a codeskulptor website, in which I had already written a python script. You just need to press the play button on the top left of your screen.

1. RPSLS  This game is called rock-paper-scissors-lizzard-spock game. It is an extention of rock-paper-scissors and first appeared in The Big Bang Theory series.

2. Number guessing game This game, as you might guess, is a number guessing game. The computer hide a number between a small number and a big number and you have finite tries to guess what number the computer is hiding.

3. Stopwatch This game will train your reflexes. It will show a stopwatch and you have to press the pause button every whole second.

4. Pong Oh, please tell me you know this game.

5. Memory There are 16 cards facing down, and all of them come in pair. Figure out the pair with the smallest number of tries.

6. Blackjack The blackjack game, yes, it is the blackjack game that you always know.

7. Asteroids Asteroids is an arcade space shooter game and I think I played this game when I was a kid. I played this game using an Atari device.

Other than those games, I made two another python scripts just for fun. The first is a fan and the second is the illustration of Hilbert’s curve. Hope you like it.

Categories: Justincase, python, Teachings

## Files output in C++

All the programs that we normally use inputs from keyboard and give outputs on the screen. However, in a large scale computation, this situation is not effective. Thus, I have learnt how to produce outputs to a file, so that it can handle a large amount of data. I learned this back in 2007 and I have already forgotten about this code. Now, if I forget about this I know where to look.

Below I wrote a bit of source code that has to be compiled in C++. This program evaluates the exponential of a number from 0 to 3 using four different ways. The first three are using the Taylor polynomial of degree 1, 2 and 3 and the fourth way is using the built in exponential function from C++ itself. The output of this program is a file called “data.dat” that consists of five columns of numbers that can be used for plotting or other programs.

```#include <iostream> #include <fstream> #include <cmath> using namespace std; double taylor(double x, int n); int factorial(int n); int main() { double number; ofstream out_stream; out_stream.open("data.dat"); for (number = 0 ; number <= 3.01 ; number = number + 0.01) { out_stream << number << " "; out_stream << taylor(number,1) << "\t"; out_stream << taylor(number,2) << "\t"; out_stream << taylor(number,3) << "\t"; out_stream << exp(number) << "\n"; } out_stream.close(); return 0; } double taylor(double x, int n) { double y=1; for(int k=1; k<=n; k++) { y = y + pow(x,k)/factorial(k); } return y; } int factorial(int n) { if (n <= 1) return 1; else return n*factorial(n-1); } ```
I then used gnuplot to plot the output of the program. The plot is the following
where column 1 is the x-axis, while columns 2,3,4 and 5 are the evaluation of exponential of x-axis using four different ways. We can see that Taylor polynomials converge to exp(x).

## Installing/Adding new latex packages in ubuntu environment

Been using ubuntu for a while, here I made some notes on how to add/install new latex packages..

A. If the package in the sty format

1. create a new directory under tex tree

–> sudo mkdir /usr/share/texmf-texlive/tex/latex/<packagename>

2. copy the package inside the new directory

3, run the following command

–> sudo mktexlsr

B. if the package is not the sty format