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+.. Objectives
+.. ----------
+   
+   .. At the end of this tutorial, you will be able to:
+   
+   ..   1. Prepare a simple shell script. 
+   ..   2. Run a script successfully and print it's result.
+   ..   3. Understand what an environment variable is.
+
+.. Prerequisites
+.. -------------
+
+..   1. Using Linux tools - Part 1
+..   2. Using Linux tools - Part 2
+..   3. Using Linux tools - Part 3
+..   4. Using Linux tools - Part 4
+..   5. Using Linux tools - Part 5
+
+ 
+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 6'.
+
+.. L2
+
+{{{ Show slide with objectives }}} 
+
+.. R2
+
+At the end of this tutorial, you will be able to,
+
+ 1. Prepare a simple shell script. 
+ #. Run a script successfully and print it's result.
+ #. Understand what an environment variable is.
+
+.. 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 5".
+
+Let us start with creating a simple shell script.
+A shell script is simply a sequence of commands, that are put into a file,
+instead of entering them one by one onto the shell. The script can then be
+run, to run the sequence of commands in a single shot instead of manually
+running, each of the individual commands. 
+For instance, let's say we wish to create a directory called ``marks`` in the
+home folder and save the results of the students into a file
+``results.txt``. 
+
+.. R4
+
+We open our editor and save the following text to ``results.sh``
+
+.. L4
+
+{{{ Open an editor and type the following }}}
+::
+
+    #!/bin/bash
+    mkdir ~/marks
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | sort > ~/marks/results.txt
+
+.. R5
+
+We can now run the script as, 
+
+.. L5
+
+{{{ Open the terminal }}}
+::
+
+    ./results.sh
+
+.. R6
+
+We get an error saying, Permission denied! Why? Can you think of the
+reason? Yes, the file doesn't have execute permissions.
+We make the file executable and then run it. 
+
+.. L6
+::
+
+    chmod u+x results.sh
+    ./results.sh
+
+.. R7
+
+We get back the prompt. We can check the contents of the file
+``results.txt`` to see if the script has run. 
+
+So, here, we have our first shell script. The first line of the script is used 
+to specify the interpreter or shell which should be used to execute the script. 
+In this case, we are asking it to use the bash shell.
+Once, the script has run, we get back the prompt. Here, we had to manually check,
+if the contents of the file are correct. It would be useful to have our script 
+print out messages. For this, we can use the ``echo`` command. We can edit our 
+``results.sh`` script, as follows.
+
+.. L7
+
+{{{ Open an editor and type the following }}}
+::
+
+    #!/bin/bash
+    mkdir ~/marks
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | sort > ~/marks/results.txt
+    echo "Results generated."
+
+.. R8
+
+Now, on running the script, we get a message on the screen informing us,
+when the script has run. 
+
+Let's now say, that we wish to let the user decide the file to which the
+results should be written to. The results file, should be specifiable by an
+argument in the command line. We can do so, by editing the file, as below. 
+
+.. L8
+
+{{{ Make the necessary changes in the previous script }}}
+
+::
+
+    #!/bin/bash
+    mkdir ~/marks
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | sort > ~/marks/$1
+    echo "Results generated."
+
+
+{{{ Highlight the text ``$1`` }}}
+
+.. R9
+
+The ``$1`` above, corresponds to the first command line argument to the
+script. So, we can run the script as shown below, to save the results to
+``grades.txt``. 
+
+.. L9
+::
+
+    ./results.sh grades.txt    
+
+.. R10
+
+When we run the ``results.sh`` file, we are specifying the location of the
+script by using ``./``. But for any of the other commands, 
+we didn't have to specify their locations. Why? The
+shell has a set of locations where it searches, for the command that we are
+trying to run. 
+
+.. L10
+
+.. L11
+
+{{{ Show slide, PATH }}}
+
+.. R11
+
+These set of locations are saved in an "environment"
+variable called PATH.let us look at what the value of the PATH variable is. To view the
+values of variables, we can use the echo command.
+
+.. L12
+
+{{{ Switch to the terminal }}}
+::
+
+    echo $PATH
+
+.. R12
+
+So, these are all the paths that are searched, when looking to execute a
+command. If we put the results.sh script in one of these locations, we
+could simply run it, without using the ``./`` at the beginning. 
+
+.. L13
+
+{{{ Show slide, variables & comments }}}
+
+.. R13
+
+As expected, it is possible to define our own variables inside our shell
+scripts. For example,
+
+.. L14
+
+{{{ Switch to the terminal }}}
+::
+
+    name="FOSSEE"
+
+.. R14
+
+It creates a new variable ``name`` whose value is ``FOSSEE``. To refer to this
+variable, inside our shell script, we would refer to it, as ``$name``.
+Note that, there is no space around the ``=`` sign. 
+
+.. L15
+::
+
+    ls $name*
+
+.. R15
+
+.. R16
+
+It is possible to store the output of a command in a variable, by enclosing
+the command in back-quotes. 
+
+.. L16
+::
+
+    count=`wc -l wonderland.txt`
+
+.. R17
+
+It saves the number of lines in the file ``wonderland.txt`` in the variable
+count. 
+
+The ``#`` character is used to comment out content from a shell script.
+Anything that appears after the ``#`` character in a line, is ignored by
+the bash shell. 
+
+.. L18
+
+.. L19
+
+{{{ Switch to 'Summary' slide }}}
+
+.. R19
+
+This brings us to the end of the end of this tutorial.
+In this tutorial, we have learnt to, 
+
+ 1. Prepare a shell script.
+ #. Display the result of a script, using the ``echo`` command.
+ #. Use the environment variable ``PATH``.
+ #. Create variables and comment out content using the ``#`` sign.
+
+.. L20
+
+{{{ Show self assessment questions slide }}}
+
+.. R20
+
+Here are some self assessment questions for you to solve
+
+.. L21
+
+{{{ Solution of self assessment questions on slide }}}
+
+.. R21
+
+And the answers,
+
+.. L22
+
+{{{ Show the Thank you slide }}}
+
+.. R22
+
+Hope you have enjoyed this tutorial and found it useful.
+Thank you!
+
+