fixing errors

1 files changed, 161 insertions, 172 deletions

diff --git a/ult/ult_5/script.rst b/ult/ult_5/script.rst
index e112ff7..2937397 100644
--- a/ult/ult_5/script.rst
+++ b/ult/ult_5/script.rst
@@ -3,17 +3,15 @@
    
    .. At the end of this tutorial, you will be able to:
    
-   ..   1. 
-   ..   2.
+   ..   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
-..   4. Using Linux tools - Part 4
-
+..   1. Getting started with Linux
+..   2. Basic File Handling
+..   4. Advanced file handling
  
 Script
 ------
@@ -26,7 +24,7 @@ team along with the logo of MHRD }}}
 .. R1
 
 Hello friends and Welcome to the tutorial on 
-'Using linux tools - Part 5'.
+'Redirection and Piping'.
 
 .. L2
 
@@ -36,11 +34,8 @@ Hello friends and Welcome to the tutorial on
 
 At the end of this tutorial, you will be able to,
 
- 1. Sort lines of text files
- #. Print lines matching a pattern
- #. Translate or delete characters
- #. Omit repeated lines.
-
+ 1. Understand what is Redirection. 
+ #. Learn the concept of Piping.
 
 .. L3
 
@@ -49,14 +44,15 @@ At the end of this tutorial, you will be able to,
 .. R3
 
 Before beginning this tutorial,we would suggest you to complete the 
-tutorial on "Using Linux tools from Part 1 to Part 4".
+former tutorials as being displayed currently.
 
 .. R4
 
-In this tutorial, we shall learn about text processing.
-TO begin with, consider data kept in two files, namely marks1.txt and 
-students.txt
-Let us see what data they contain. Open a terminal and type, 
+Let us begin with the concept of 'Redirection and Piping'  which 
+performs the  same operations as the ``cut`` and ``paste`` commands.
+
+Consider the files ``marks.txt`` and ``students.txt``.The contents of 
+the files  are as following:
 
 .. L4
 
@@ -68,274 +64,267 @@ Let us see what data they contain. Open a terminal and type,
 
 .. R5
 
-Let's say we wish to sort the output in the alphabetical order
-of the names of the files. We can use the ``sort`` command for this
-purpose.
-
-We just pipe the previous output to the ``sort`` command as,
+Now, let us view the contents of both these files side-by-side.
 
 .. L5
 ::
 
-    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -
 
 .. R6
 
-Let's say we wish to sort the names, based on the marks in the first
-subject i.e. the first column after the name. ``sort`` command also allows us to
-specify the delimiter between the fields and sort the data on a particular
-field. ``-t`` option is used to specify the delimiter and ``-k`` option
-is used to specify the field. 
+Now, in order to view the same output in a new file at an other 
+location, we say,
 
 .. L6
 ::
 
-    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort -t " " -k 2
+    cut -d " " -f 2- marks1.txt > /tmp/m_tmp.txt
+    paste -d " " students.txt m_tmp.txt
 
-.. L7
+.. R7
 
-{{{ Show slide with, Sort... }}}
+First, let us try to understand the second solution,which is a two 
+step approach.
+Later, we shall look at the first solution. 
 
-.. R7
+.. L7
+
+.. L8
 
-This command give us a sorted output as required. But, what if we would 
-like the output to appear in the reverse order. ``-r`` option allows the output
-to be sorted in the reverse order and the ``-n`` option is used to choose 
-a numerical sorting. 
+{{{ Show slide, with Redirection }}}
 
 .. R8
 
-Let us do it on the terminal and see for ourselves, 
+The standard output, in general, goes to the display.
+But, this may not be what we always require. 
 
-.. L8
+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,
 
-{{{ Switch to the terminal }}}
-::
+    command > file1
 
-    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| 
-    sort -t " " -k 2 -rn
+.. L9
+
+{{{ Show slide, with Redirection.. }}}
 
 .. R9
 
-Suppose, While you are compiling the student marklist, Anne walks up to you and
-wants to know her marks. You, being a kind person that you are, oblige.
-But you do not wish to her to see the marks that others have scored. What
-do you do? Here, the ``grep`` command comes to your rescue. 
+Similarly, the standard input (stdin) can be redirected as,
+    
+    command < file1
 
-``grep`` is a command line text search utility. You can use it to search
-for Anne and show her, what she scored. ``grep`` allows us to search for a
-search string in files. But we could, like any other command, pipe the
-output of other commands to it. So, we shall use the previous combination
-of cut and paste that we had, to get the marks of students along with their
-names and search for Anne in that. 
+The input and the output redirection could be combined in a single command, 
+as, 
 
-.. L9
-::
+    command < infile > outfile
 
-    cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep Anne 
+.. L10
 
-.. R10
+{{{ Show slide, with stderr }}}
 
-This will give us only the line containing the word Anne as the output.
-The grep command is by default case-sensitive. So, we wouldn't have got
-the result if we had searched for anne, with a small a, instead of 
-Anne, with a capital a. But, what if we didn't know, whether the name was 
-capitalized or not? ``grep`` allows you to do case-insensitive searches 
-by using the ``-i`` option. 
 
-.. L10
-::
+.. R10
 
-    cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep -i Anne 
+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. 
 
 .. R11
 
-Now, in another scenario, if we wished to print all the lines, which do
-not contain the word Anne, we could use the ``-v`` option. 
+For instance, let's reproduce an error using the ``cut`` command used
+before. We shall change the ``-f`` option to ``-c`` 
 
 .. L11
+
+{{{ Switch to terminal }}}
 ::
 
-    cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep -iv Anne
+    cut -d " " -c 2- marks1.txt > /tmp/m_tmp.txt
 
 .. R12
 
-grep allows us to do more complex searches, for instance, searching for
-sentences starting or ending with a particular pattern and regular
-expression based searches. 
-
-{{{ Show slide with, tr }}}
-
-``tr`` is a command that takes two sets of characters as parameters, and
-replaces occurrences of the characters in the first set with the
-corresponding elements from the other set. It reads from the standard
-output and writes to the standard output. 
-
-For instance, if we wish to replace all the lower case letters in the
-students file with upper case, we can do it as, 
+This displays an error saying that the delimiter option should be used 
+with the fields option only. You may verify this by looking at the 
+``m_tmp.txt`` file, which is now empty.We can now, redirect the 
+``stderr`` also to a file, instead of showing it on the display. 
 
 .. L12
-
-{{{ Switch to the terminal }}}
 ::
 
-    cat students.txt | tr a-z A-Z
+    cut -d " " -f 2- marks1.txt 1> /tmp/m_tmp.txt 2> /tmp/m_err.txt
 
 .. R13
 
-A common task is to remove empty newlines from a file. The ``-s`` flag
-causes ``tr`` to compress sequences of identical adjacent characters in its
-output to a single token. For example,
+The above command redirects all the errors to the ``m_err.txt`` file
+and the output to the ``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.
 
 .. L13
 ::
 
-    tr -s '\n' '\n'
+    paste -d " " students.txt m_tmp.txt
 
 .. R14
 
-Hit enter 2-3 times and see that every time we hit enter we get a newline.
+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. 
 
 .. L14
 ::
 
-    <Enter>
-    <Enter> 
+    cut -d " " -f 2- marks1.txt | paste -d " " students.txt -
+
+.. L15
+
+{{{ Show slide, with Piping }}}
 
 .. R15
 
-It replaces sequences of one or more newline characters with a single newline.
+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 ``-d`` flag causes ``tr`` to delete all tokens of the specified set of
-characters from its input. In this case, only a single character set
-argument is used. The following command removes carriage return characters,
-thereby converting a file in DOS/Windows format to the Unix format. 
+Now, let us observe the ``cut`` command. If we look at the command only 
+upto the ``|`` character, it appears as a normal ``cut`` command .
 
-.. L15
-::
+.. L16
 
-    cat foo.txt | tr -d '\r' > bar.txt
+{{{ Show slide, with Piping.. }}}
 
 .. R16
 
-The ``-c`` flag complements the first set of characters.
+So, the ``|`` character here, seems 
+to be joining the two 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 the input from the ``stdin``. 
+This activity is commonly called piping and the character ``|`` is called 
+a pipe. 
 
-.. L16
-::
+.. L17
 
-    tr -cd '[:alnum:]' 
+{{{ Show slide, with Piping... }}}
 
 .. R17
 
-It therefore removes all non-alphanumeric characters.
+This is roughly equivalent to using two redirects and a temporary file.
 
-Let us consider one more scenario.Suppose we have a list of items, say books, 
-and we wish to obtain a list which names of all the books only once, without 
-any duplicates. To achieve this, we use the ``uniq`` command. Let us first 
-have a look at our file
+    command1 > tempfile
+    command2 < tempfile
+    rm tempfile
 
-.. L17
-::
+Also, given that a pipe is just a way to send the output of a 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 therefore it should
+ be noted that it is not restricted to only two commands. 
 
-    cat items.txt
+.. L18
 
-.. R18
+{{{ Switch to Summary slide }}}
 
-Now, let us try and get rid of the duplicate lines from this file using 
-the ``uniq`` command.
+.. R18
 
-.. L18
-::
+This brings us to the end of the end of this tutorial.
+In this tutorial, we have learnt to,
 
-    uniq items.txt
+ 1. Use the ``cut`` and ``paste`` commands in redirection.
+ 2. Use the pipe ( | ) character. 
+ 
+.. L19
+ 
+{{{ Show self assessment questions slide }}}
 
 .. R19
 
-Nothing happens! Why? The ``uniq`` command removes duplicate lines only when 
-they are next to each other. So, henceforth, we get a sorted file from the 
-original file and work with that file. 
+Here are some self assessment questions for you to solve:
 
-.. L19
-::
+1. How will you redirect the content of a file to a device ?
+
+2. How to view last field(30), in a file located at /home/test.txt whose
+   first line is "data:myscripts:20:30"
+    
+    - cut -d : -f 4 /home/test.txt
+    - cut -f 3 /home/test.txt
+    - cut -d : -f 3 /home/test.txt
+   
+
+.. L20
 
-    sort items.txt | uniq
+{{{ Solutions for the self assessment questions on slide }}}
 
 .. R20
 
-``uniq -u`` command gives the lines which are unique and do not have any 
-duplicates in the file. ``uniq -d`` outputs only those lines which 
-have duplicates. 
+And the answers:
 
-.. L20 
+1. A file can be redirected to a device as,
+::
+   
+    cat filename > device
+For eg:
 ::
 
-    uniq -u items-sorted.txt 
-
-.. R21
+    cat sound.wav > /dev/audio  
+    
 
-The ``-c`` option displays the number of times each line occurs in the file.
+2. The correct option would be
+::
+    
+    cut -d : -f 4 /home/test.txt
 
 .. L21
-::
 
-    uniq -dc items-sorted.txt
+{{{ Show the SDES & FOSSEE slide }}}
+
+.. R21
+
+Software Development techniques for Engineers and Scientists - SDES, is an 
+initiative by FOSSEE. For more information, please visit the given link.
+
+Free and Open-source Software for Science and Engineering Education - FOSSEE, is
+based at IIT Bombay which is funded by MHRD as part of National Mission on 
+Education through ICT.
 
 .. L22
 
-{{{ Show summary slide }}}
+{{{ Show the ``About the Spoken Tutorial Project'' slide }}}
 
 .. R22
 
-This brings us to the end of the end of this tutorial.
-In this tutorial, we have learnt to, 
- 
-  1. Use the ``sort`` command to sort lines of text files.
-  #. Use the ``grep`` command to search text pattern.
-  #. Use the ``tr`` command to translate and/or delete characters.
-  #. Use the ``uniq`` command to omit repeated lines in a text. 
+Watch the video available at the following link. It summarises the Spoken 
+Tutorial project.If you do not have good bandwidth, you can download and 
+watch it. 
 
 .. L23
 
-{{{ Show self assessment questions slide }}}
+{{{ Show the `` Spoken Tutorial Workshops'' slide }}}
 
 .. R23
 
-Here are some self assessment questions for you to solve
+The Spoken Tutorial Project Team conducts workshops using spoken tutorials,
+gives certificates to those who pass an online test.
 
- 1. To obtain patterns; one per line, which of the following command is used ?
-   
-    - grep -f
-    - grep -i
-    - grep -v
-    - grep -e
-
- 2. Translate the word 'linux' to upper-case.
-
- 3. Sort the output of the ``ls -al`` command.
+For more details, contact contact@spoken-tutorial.org
 
 .. L24
 
-{{{ Solution of self assessment questions on slide }}}
+{{{ Show the ``Acknowledgements'' slide }}}
 
 .. R24
 
-And the answers,
-
- 1. In order to obtain patterns one per line, we use the ``grep`` command
-    alongwith the -f option.
-
- 2. We use the tr command to change the word into uppercase 
-::
-
-    echo 'linux' | tr a-z A-Z
- 
-
- 3. We use the sort command as, 
-::
-     
-    ls -al | sort -n -k5
-The -n  means "sort numerically", and the -k5 option means to key off of 
-column five. 
+Spoken Tutorial Project is a part of the "Talk to a Teacher" project.
+It is supported by the National Mission on Education through ICT, MHRD, 
+Government of India. More information on this mission is available at the 
+given link.
 
 .. L25