\documentclass{beamer}
%include lhs2TeX.fmt
\author{Piyush P Kurur\\
  Office no: 224\\
  Dept. of Comp. Sci. and Engg.\\
  IIT Kanpur}


\newcommand{\Token}[2][]{\node(#2#1)[token]{#2};}
\newcommand{\Symbol}[2][]{\node(#2#1)[symbol]{#2};}
\newcommand{\Point}[1]{\node(#1)[point]{#1};}

\usepackage{tikz}
\usetikzlibrary{positioning,shapes,chains,fit,shadows}
\usetikzlibrary{shapes.symbols}
\usetikzlibrary{matrix}
\usetikzlibrary{backgrounds}
\usetikzlibrary{shapes.geometric}
\usepackage{multicol}

\usepackage{algorithm2e}
\usepackage{pgfkeys}

\pgfkeys {%
  /tikz/oval/.style={%
    shape=ellipse,
    inner sep=1pt,
    drop shadow,
    draw = black
  },
  /tikz/redbox/.style={%
    shape=rectangle,%
    minimum size=1.5em,%
    top color = white, %
    bottom color=red!50!black!50,
    inner sep=0pt,
    draw=black
  },
  /tikz/null/.style={%
    shape=circle,
    minimum size=0.5em,
    draw=black,
  },
  /tikz/greybox/.style={ 
    shape=rectangle,%
    minimum width=7em,%
    minimum height=1.5em,
    fill=black!20,
    inner sep=0pt,
    draw=black
  },
  /tikz/blackbox/.style={ 
    shape=rectangle,%
    minimum width=7em,%
    minimum height=1.5em,
    fill=black,
    inner sep=0pt,
    draw=black
   },
  /tikz/whitebox/.style={
    shape=rectangle,
    minimum width=7em,
    minimum height=1.5em,
    draw=black
  },
  /tikz/bluebox/.style={
    shape=rectangle,
    minimum width=7em,
    minimum height=1.5em,
    fill=blue!40,
    draw=black
  },
  /tikz/whitetape/.style={
    shape=rectangle,
    minimum width=4em,
    minimum height=1.5em,
    draw=black
  },
  /tikz/bluearr/.style={
    ->,
    line width=0.25em, 
    draw=blue!40
  },
  /tikz/greenarr/.style={
    ->,
    line width=0.25em, 
    draw=green!40!black!60
  }
}
    
\newcommand{\arraythree}[4]{
  \begin{tikzpicture}[node distance=0]
    \pgfsetstrokeopacity{#4};
    \node[#1](a0#3){#2};
    \node[#1, right=of a0#3](a1#3){#2};
    \node[#1, right=of a1#3](a1#3){#2};
  \end{tikzpicture}
}

\newcommand{\arraytwo}[4]{
  \begin{tikzpicture}[node distance=0]
    \pgfsetstrokeopacity{#4};
    \node[#1](a0#3){#2};
    \node[#1,right=of a0#3]{#2};
  \end{tikzpicture}
}
  
\newcommand{\Array}[0]{
  \arraythree{box}{}{a}{1}
}

\newcommand{\AArray}[0]{%
  \arraythree{bbox}{\Array}{b}{0.5}}
\newcommand{\AAArray}[0]{%
  \arraytwo{bbbox}{\AArray}{c}{0.25}}

    
    
\newcommand{\T}[1]{\ensuremath{T\left(#1\right)}}  
\newcommand{\BigOh}[1]{\ensuremath{O\left(#1\right)}}
\title{Fundamentals of Computing: Lecture 38}
\date{November 11, 2009}
\begin{document}
\begin{frame}
  \maketitle
\end{frame}


\begin{frame}
  \frametitle{Summary of last class}
  \begin{itemize}
  \item Simple shell program.
    \begin{spec}
$ cmd arg1 arg2 arg3
    \end{spec}
    \pause
  \item |stdin|/|stdout|/|stderr| redirection 
    \pause
    \begin{spec}
$ cmd arg1 arg2 <foo   # get input from foo
$ cmd arg >bar
    \end{spec}
    \pause
    \begin{spec}
$ cmd 2>&1 | less      # 0-stdin 1-stdout 2-stderr 
$ cmd >>foo            # append to the file foo instead of write
    \end{spec}
    \pause
  \item Pipes 
    \begin{spec}
$ cmd1 | cmd2 | cmd3 | cmd 
    \end{spec}
\end{itemize}

\end{frame}

\begin{frame}
  \frametitle{Shell variables}
  
  To assign a shell variable
  \begin{spec}
$ foo=bar    # no space between foo and bar
  \end{spec}
  \pause
  To get the value of foo use |$foo|
  \begin{spec}
$ echo the value of variable foo is $foo
  \end{spec}
  \pause
  \begin{block}
    {Some important shell variables}
    \begin{itemize}
    \item |PATH| The directories where an executable is searched
      \begin{spec}
$ export PATH=/bin/:/usr/bin:/usr/local/bin:
      \end{spec}
    \item |PS1| The first prompt
    \item |PS2| the second prompt etc
    \end{itemize}
  \end{block}
\end{frame}
\begin{frame}
  \frametitle{Funny characters}
  
  Shell interpretes some characters differently 
  We have already seen some |<|, |>|, |&|, | || | etc.
  \pause
  The character '*' means any sequece of characters
  \pause
  \begin{spec}
$ ls *.c
$ rm *.o
  \end{spec}
\end{frame}
\begin{frame}
  \begin{block}{Protecting characters}
    \begin{itemize}
    \item Use |\| to protect funny characters
      \pause
      \begin{spec}
$ ls filename\ with\ spaces
$ echo I am an invisible file > \ 
      \end{spec}
      \pause
    \item Quoting with |'| 
      \pause
      \begin{spec}
$ ls 'filename with spaces'
$ rm '*'   # actually removes a file called *
$ echo I am an invisible file > ' '
      \end{spec}
 \pause     
    \item Double quoting |"|. Similar to |'| but shell variables expand
      \begin{spec}
$ foo=bar
$ echo '$foo is the value of foo'
$ ech "$foo is the value of foo"
      \end{spec}
    \end{itemize}
    
  \end{block}
    
\end{frame}

\begin{frame}
  \frametitle{The program |grep|}
  grep is a \emph{filter}. It sends only those lines where a
  given pattern matches.
  \pause
  \begin{spec}
    grep PATTERN file1 file2 file3
    grep PATTERN
  \end{spec}
  
  The pattern can be what is called a regular expression
  \pause
  eg. Print all the hidden files (files with name staring with a .)
  \pause
  \begin{spec}
  ls | grep '^\..*' | less # 
  \end{spec}
  \pause
  \begin{itemize}
  \item |^| means start of the line
  \item |.| means any character
  \item |r *| means many |r|'s
  \item I have written the |\.| to \emph{escape} the special meaning
  \end{itemize}
\end{frame}

\end{document}





\begin{frame}
  \frametitle{Philosophy of shell programming} 

  There any many small but efficient programs.  Combine them.
  
  You need to know many of these common programs.
  
  \begin{itemize}
  \item |echo| prints its command line arguments
    \pause
  \item |less| shows int |stdin| in pages
    \begin{spec}
      $ cmd | less
      $ less foo bar biz
    \end{spec}
    \pause
  \item |grep pattern| shows only those lines of its stdin that
    matches the pattern.
  \end{itemize}
  \pause
  There are many more. 
  \pause
  To learn more, use command prompt always and read manpages.
\end{frame}