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+.. Objectives
+.. ----------
+   
+   .. At the end of this tutorial, you will be able to:
+   
+   ..   1. Understand what is Redirection and Piping.
+   ..   2. Learn various features of shell.
+
+.. Prerequisites
+.. -------------
+
+..   1. Using Linux tools - Part 1
+..   2. Using Linux tools - Part 2
+..   3. Using Linux tools - Part 3
+ 
+Script
+------
+
+.. L1
+
+{{{ Show the  first slide containing title, name of the production
+team along with the logo of MHRD }}}
+
+.. R1
+
+Hello friends and Welcome to the tutorial on 
+'Using linux tools - Part 4'.
+
+.. L2
+
+{{{ Show slide with objectives }}} 
+
+.. R2
+
+At the end of this tutorial, you will be able to,
+
+ 1. Understand what is Redirection and Piping. 
+ #. Learn various features of the shell.
+
+.. L3
+
+{{{ Switch to the pre-requisite slide }}}
+
+.. R3
+
+Before beginning this tutorial,we would suggest you to complete the 
+tutorial on "Using Linux tools from Part 1 to Part 3".
+
+.. R4
+
+Let us begin with the concept of 'Redirection and Piping'  which can do the 
+same operations as the ``cut`` and ``paste`` commands.
+
+Consider the files ``marks.txt`` and ``students.txt``, which has the 
+following contents
+
+.. L4
+
+{{{ Open the terminal }}}
+::
+
+    cat marks1.txt
+    cat students.txt
+
+.. R5
+
+Let us view the contents of both the files side-by-side
+
+.. L5
+::
+
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -
+
+.. R6
+
+Now, in order to view the same ouput in a file at a new location, we say,
+
+.. L6
+::
+
+    cut -d " " -f 2- marks1.txt > /tmp/m_tmp.txt
+    paste -d " " students.txt m_tmp.txt
+
+.. R7
+
+Let's first try to understand the second solution, which is a two step
+solution. Later, we shall look at the first solution. 
+
+.. L7
+
+.. L8
+
+{{{ Show slide, with Redirection }}}
+
+.. R8
+
+The standard output, in general, goes to the display.
+Hence, the output of the commands that we type, come out to the display.
+This may not always be what we require. 
+
+For instance, in the solution above, we use the cut command and get only
+the required columns of the file and write the output to a new temporary
+file. The ``>`` character is used to state that we wish to redirect the
+output, and it is followed by the location to which we wish to redirect. 
+For example,
+
+    command > file1
+
+.. L9
+
+{{{ Show slide, with Redirection... }}}
+
+.. R9
+
+Similarly, the standard input (stdin) can be redirected as,
+    
+    command < file1
+
+The input and the output redirection could be combined in a single command, as, 
+
+    command < infile > outfile
+
+There is actually a third kind of standard stream, called the Standard
+error (stderr). Any error messages that you get, are coming through this
+stream. Like ``stdout``, ``stderr`` also streams to the display by default,
+but it could be redirected to a file, as well. 
+
+.. R10
+
+For instance, let's introduce an error into the ``cut`` command used
+before. We change the ``-f`` option to ``-c`` 
+
+.. L10
+
+{{{ Switch to terminal }}}
+::
+
+    cut -d " " -c 2- marks1.txt > /tmp/m_tmp.txt
+
+.. R11
+
+This prints an error that says the delimiter option should be used with the
+fields option only, and you can verify that the ``m_tmp.txt`` file is
+empty.  We can now, redirect the ``stderr`` also to a file, instead of
+showing it on the display. 
+
+.. L11
+::
+
+    cut -d " " -f 2- marks1.txt 1> /tmp/m_tmp.txt 2> /tmp/m_err.txt
+
+.. R12
+
+The above command redirects all the errors to the ``m_err.txt`` file
+and the output to ``m_tmp.txt`` file. When redirecting, 1 stands
+for ``stdout`` and 2 stands for ``stderr``. 
+
+Let us complete the solution by using the ``paste`` command
+
+.. L12
+::
+
+    paste -d " " students.txt m_tmp.txt
+
+.. R13
+
+So, in two steps we solved the problem of getting rid of the roll numbers
+from the marks file and displaying the marks along with the names of the
+students. Now, that we know how to redirect output, we could choose to
+write the output to a file, instead of showing on the display. 
+
+Let us now look at the first solution. 
+
+.. L13
+::
+
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -
+
+.. L14
+
+{{{ Show slide, with Piping }}}
+
+.. R14
+
+First of all, the hyphen at the end is to ask the paste command to read the
+standard input, instead of looking for a FILE. The ``man`` page of ``paste``
+command gives us this information. 
+
+The character ``|`` is called a pipe. 
+Now, what is happening with the ``cut`` command. If we look at the command only 
+up to the ``|`` character, it is a normal ``cut`` command . So, the ``|`` seems 
+to be joining the commands in some way. 
+Essentially, what we are doing is, to redirect the output of the first
+command to ``stdin`` and the second command takes input from the ``stdin``. 
+
+More generally, 
+
+    command1 | command2
+
+executes ``command1`` and sends it's output to the ``stdin``, which is then
+used as the input for ``command2``. This activity is commonly called piping.
+
+.. L15
+
+{{{ Show slide, with Piping... }}}
+
+.. R15
+
+This is roughly equivalent to using two redirects and a temporary file 
+
+    command1 > tempfile
+    command2 < tempfile
+    rm tempfile
+
+Also, given that a pipe is just a way to send the output of the command to
+the ``stdin``, it should be obvious, to you that we can use a chain of
+pipes. Any number of commands can be piped together and you need not be
+restricted to two commands. 
+
+The Bash shell has some nice features, that make our job of using the shell
+easier and much more pleasant. We shall look at a few of them, here. 
+
+Bash provides the feature of tab completion. What does tab completion mean?
+When you are trying to type a word and you have entered enough portion of the 
+word, bash can complete the word for you, by hitting the tab key. 
+
+If on hitting the tab key, the word doesn't get completed, either the word
+doesn't exist or the word cannot be decided unambiguously. If the case is
+the latter one, hitting the tab key a second time, will list the
+possibilities.
+
+.. L16
+
+{{{ Show slide, with Tab-completion }}}
+
+.. R16
+
+Bash provides tab completion for the following. 
+
+  1. File Names
+  2. Directory Names
+  3. Executable Names
+  4. User Names (when they are prefixed with a ~)
+  5. Host Names (when they are prefixed with a @)
+  6. Variable Names (when they are prefixed with a $) 
+
+.. R17
+
+For example, 
+
+.. L17
+
+{{{ Switch to terminal }}}
+::
+
+    pas<TAB><TAB>
+    ~/<TAB><TAB>
+
+.. R18
+
+Bash also saves the history of the commands you have typed. So, you can go
+back to a previously typed command and use the up and down arrow keys to
+navigate in your bash history. 
+
+.. L18
+::
+
+    <UP-ARROW>
+
+.. R19
+
+You can also search incrementally, for commands in your bash history.
+``Ctrl-r`` searches for the commands that you have typed before. But, note
+that the number of commands saved in the history is limited, generally upto
+a 1000 commands. 
+
+.. L19
+::
+
+   <Ctrl-r> pas
+
+.. R20
+
+Unix recognizes certain special characters, called "meta characters," as
+command directives. The shell meta characters are recognized anywhere they
+appear in the command line, even if they are not surrounded by blank space.
+For that reason, it is safest to only use the characters A-Z, a-z, 0-9, and
+the period, dash, and underscore characters when naming files and
+directories on Unix. If your file or directory has a shell meta character
+in the name, you will find it difficult to use the name in a shell command.
+
+.. L20
+
+.. L21
+
+{{{ Show slide, with Shell Meta Characters }}}
+
+.. R21
+
+The characters that you can see on the slide are the shell meta characters
+
+.. R22
+
+Lets take an example,
+
+.. L22
+
+{{{ Switch to terminal }}}
+::
+
+    ls file.?
+
+.. R23
+
+It means, run on a directory containing the files file, file.c, file.lst, 
+and myfile would list the files file.c and file.lst. However,
+
+.. L23
+::
+
+    ls file.?
+
+.. R24
+
+Run on the same directory would only list file.c because the ? only matches
+one character, no more, no less. This can save you a great deal of typing
+time. 
+
+For example, if there is a file called
+california_cornish_hens_with_wild_rice and no other files whose names begin
+with 'c', you could view the file without typing the whole name by typing
+this
+
+.. L24
+::
+
+    more c*
+
+.. R25
+
+Here, the c* matches that long file name.
+File-names containing meta characters can pose many problems and should
+never be intentionally created.
+
+.. L25
+
+.. L26
+
+{{{ Switch to Summary slide }}}
+
+.. R26
+
+This brings us to the end of the end of this tutorial.
+In this tutorial, we have learnt to,
+
+ 1. Use the ``cut`` and ``paste`` commands in redirection.
+ #. Use the pipe ( | ) character. 
+ #. Implement features of shell like tab-completion and history.
+
+.. L27
+ 
+{{{ Show self assessment questions slide }}}
+
+.. R27
+
+Here are some self assessment questions for you to solve
+
+.. L28
+
+{{{ Solution of self assessment questions on slide }}}
+
+.. R28
+
+And the answers,
+
+.. L29
+
+{{{ Show the Thank you slide }}}
+
+.. R29
+
+Hope you have enjoyed this tutorial and found it useful.
+Thank you!
+