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+.. Objectives
+.. ----------
+   
+   .. At the end of this tutorial, you will be able to:
+   
+   ..   1. Display the contents of files.
+   ..   2. Read only parts of a file.
+   ..   3. Look at the statistical information of a file.
+
+.. Prerequisites
+.. -------------
+
+..   1. Using Linux tools - Part 1
+..   2. Using Linux tools - Part 2
+ 
+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 3'.
+
+.. L2
+
+{{{ Show slide with objectives }}} 
+
+.. R2
+
+At the end of this tutorial, you will be able to,
+
+ 1. Display the contents of files.
+ #. Read only parts of a file.
+ #. Look at the statistical information of a file.
+
+.. L3
+
+{{{ Switch to the pre-requisite slide }}}
+
+.. R3
+
+Before beginning this tutorial,we would suggest you to complete the 
+tutorial on "Using Linux tools - Part 1" and "Using Linux tools - Part 2".
+
+.. R4
+
+Let us begin with how to read a while as a whole.
+The ``cat`` command is the most commonly used command to display the
+contents of files. To view the contents of a file, say, ``foo.txt``, we
+simply say, 
+
+.. L4
+::
+
+    cat foo.txt
+
+.. R5
+
+You can see the contents of the file on the terminal. 
+
+The cat command could also be used to concatenate the text of multiple
+files. Say, we have two files,``foo.txt`` and ``bar.txt``, 
+
+.. L5
+::
+
+    cat foo.txt bar.txt
+
+.. R6
+
+It shows the output of both the files concatenated on the standard output. 
+But if we had a long file,the output of ``cat`` command is not convenient 
+to read.
+Let's look at the ``less`` command which turns out to be more useful in 
+such a case. 
+
+``less `` allows you to view the contents of a text file one screen at a
+time. 
+
+.. L6
+::
+
+    less wonderland.txt
+
+.. R7
+
+This shows us the file, one screen at a time.
+
+.. L7
+
+.. L8
+
+{{{ Show slide with, less }}}
+
+.. R8
+
+``less`` has a list of commands that it allows you to use, once you have
+started viewing a file. A few of the common ones have been listed below. 
+
+    * q: Quit.
+
+    * [Arrows]/[Page Up]/[Page Down]/[Home]/[End]: Navigation.
+
+    * ng: Jump to line number n. Default is the start of the file.
+
+    * /pattern: Search for pattern. Regular expressions can be used.
+
+    * h: Help. 
+
+.. R9
+
+Let us move ahead with the topic. Often we just would like to get some 
+statistical information about the file, rather than viewing the contents 
+of the file. The ``wc`` command prints these details for a file. 
+
+.. L9
+::
+
+    wc wonderland.txt
+
+.. L10
+
+{{{ Highlight the required portions accordingly while narrating }}}
+
+.. R10
+
+As you can see, we get some information about the file.
+The first number is the number of lines, the second is the number of words
+and the third is the number of characters in the file. 
+
+.. R11
+
+Let us now look at a couple of commands that let you see parts of files,
+instead of the whole file. The ``head`` and ``tail`` commands let you see 
+parts of files, as their names suggest, the start and the end of a file,
+respectively. 
+
+.. L11
+::
+
+    head wonderland.txt
+
+.. R12
+
+It prints only the first 10 lines of the file. Similarly tail will print the
+last 10 lines of the file. If we wish to change the number of lines that we
+wish to view, we use the option ``-n``. 
+
+.. L12
+::
+
+    head -n 1 wonderland.txt
+
+.. R13
+
+It prints only the first line of the file. Similarly, we could print only
+the last line of the file.
+
+The most common use of the tail command is to monitor a continuously
+changing file, for instance a log file. Say you have a process running,
+which is continuously logging it's information to a file, for instance the
+logs of the system messages. 
+
+.. L13
+::
+
+    tail -f /var/log/dmesg
+
+.. R14
+
+This will show the last 10 lines of the file as expected, but along with
+that, it starts monitoring the file. Any new lines added at the end of the
+file, will be shown. To interrupt tail, while it is monitoring, hit
+``Ctrl-C``. which will stop any process that is running from your
+current shell. 
+
+We looked at a couple of functions that allowed us to view a part of a file,
+line-wise. We shall now look at a couple of commands that will allow us to look
+at only certain sections of each line of a file and merge those parts.
+Let's take the ``/etc/passwd`` file as our example file. It contains
+information about each user of the system.
+
+.. L14
+::
+
+    cat /etc/passwd
+
+.. R15
+
+In the output, let us look at only the first, fifth, sixth and the last 
+columns.The first column is the user name, the fifth column is the user info, 
+the sixth column is the home folder and the last column is the path of the 
+shell program that the user uses. 
+Let's say we wish to look at only the user names of all the users in the
+file, how do we do it?
+
+.. L15
+::
+    
+    cut -d : -f 1 /etc/passwd
+
+.. R16
+
+It gives us the required output. Let us understand this operation in detail.
+The first option ``-d`` specifies the delimiter between the various fields in
+the file, in this case it is the semicolon. If no delimiter is specified,
+the TAB character is assumed to be the delimiter. The ``-f`` option specifies,
+the field number that we want to choose. 
+You can print multiple fields, by separating the field numbers with a
+comma. 
+
+Pause the video here, try out the following exercise and resume the video.
+
+.. L16
+
+.. L17
+
+{{{ Show slide with exercise 3 }}}
+
+.. R17
+
+Print only the first, fifth and the seventh fields of the file ``/etc/passwd``.
+
+.. R18
+
+Switch to the terminal for solution
+
+.. L18
+
+{{{ continue from paused state }}}
+{{{ Switch to the terminal }}}
+
+::
+    
+    cut -d : -f 1,5,7 /etc/passwd
+
+.. R19
+
+We get the correct output.
+Instead of choosing by fields, ``cut`` also allows us to choose on the
+basis of characters or bytes. For instance, we could get the first 4
+characters of all the entries of the file, ``/etc/passwd`` by saying,
+
+.. L19
+::
+
+    cut -c 1-4 /etc/passwd 
+
+.. R20
+
+The end limits of the ranges can take sensible default values, if they are
+left out. For example, 
+
+.. L20
+::
+
+    cut -c -4 /etc/passwd 
+
+.. R21
+
+It gives the same output as before. If the start position has not been
+specified, it is assumed to be the start of the line. Similarly if the end
+position is not specified, it is assumed to be the end of the line. 
+
+.. L21
+::
+
+    cut -c 10- /etc/passwd 
+
+.. R22
+
+It prints all the characters from the 10th character up to the end of the
+line. 
+Let us now solve an inverse problem. Let's say we have two columns of data
+in two different files, and we wish to view them side by side. 
+
+.. L22
+
+.. L23
+
+{{{ Show slide with, paste }}}
+
+.. R23
+
+For instance, given a file containing the names of students in a file,
+students.txt, and another file with the marks of the students,marks.txt,
+
+.. R24
+
+we wish to view the contents, side by side. The ``paste`` command allows 
+us to do that. 
+
+.. L24
+::
+
+    paste students.txt marks.txt
+    paste -s students.txt marks.txt
+
+.. R25
+
+The first command gives us the output of the two files, next to each other
+and the second command gives us the output one below the other. 
+
+Now, this problem is a bit unrealistic because, we wouldn't have the marks
+of students in a file, without any information about the student to which
+they belong. Let's say our marks file had the first column as the roll
+number of the student, followed by the marks of the students. What would we
+then do, to get the same output that we got before? 
+
+Essentially we need to use both, the ``cut`` and ``paste`` commands, but
+how do we do that? That brings us to the concept of Redirection and Piping
+which is covered in the next spoken tutorial. 
+
+.. L25
+
+.. L26
+
+{{{ Switch to summary slide }}}
+
+.. R26
+
+This brings us to the end of this tutorial.
+In this tutorial, we have learnt to, 
+
+ 1. Display the contents of files using the ``cat`` command.
+ #. View the contents of a file one screen at a time using the 
+    ``less`` command.
+ #. Display specific contents of file using the ``head`` and 
+    ``tail`` commands.
+ #. Use the ``cut``, ``paste`` and ``wc`` commands.
+  
+.. L27
+
+{{{ Show self assessment questions slide }}}
+
+.. R27
+
+Here are some self assessment questions for you to solve
+
+1. How to view lines from 1 to 15 in wonderland.txt?
+
+2. In ``cut`` command, how to specify space as the delimiter? 
+
+.. L28
+
+{{{ Solution of self assessment questions on slide }}}
+
+.. R28
+
+And the answers,
+
+1. We can use the head command as,
+::
+
+    head -15 wonderland.txt
+
+2. We use the -d option with the command as,
+::
+
+    cut -d " " <filename>
+
+.. L29
+
+{{{ Show the Thank you slide }}}
+
+.. R29
+
+Hope you have enjoyed this tutorial and found it useful.
+Thank you!
+