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diff --git a/ult/ult_5/script.rst b/ult/ult_5/script.rst deleted file mode 100644 index e112ff7..0000000 --- a/ult/ult_5/script.rst +++ /dev/null @@ -1,347 +0,0 @@ -.. Objectives -.. ---------- - - .. At the end of this tutorial, you will be able to: - - .. 1. - .. 2. - -.. 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 - - -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 5'. - -.. L2 - -{{{ Show slide with objectives }}} - -.. R2 - -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. - - -.. 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 4". - -.. 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, - -.. L4 - -{{{ Open the terminal }}} -:: - - cat marks1.txt - cat students.txt - -.. 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, - -.. L5 -:: - - cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort - -.. 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. - -.. L6 -:: - - cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| sort -t " " -k 2 - -.. L7 - -{{{ Show slide with, Sort... }}} - -.. R7 - -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. - -.. R8 - -Let us do it on the terminal and see for ourselves, - -.. L8 - -{{{ Switch to the terminal }}} -:: - - cut -d " " -f 2- marks1.txt | paste -d " " students.txt -| - sort -t " " -k 2 -rn - -.. 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. - -``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. - -.. L9 -:: - - cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep Anne - -.. R10 - -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 -:: - - cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep -i Anne - -.. 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. - -.. L11 -:: - - cut -d " " -f 2- marks1.txt | paste -d " " students.txt - | grep -iv Anne - -.. 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, - -.. L12 - -{{{ Switch to the terminal }}} -:: - - cat students.txt | tr a-z A-Z - -.. 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, - -.. L13 -:: - - tr -s '\n' '\n' - -.. R14 - -Hit enter 2-3 times and see that every time we hit enter we get a newline. - -.. L14 -:: - - <Enter> - <Enter> - -.. R15 - -It replaces sequences of one or more newline characters with a single newline. - -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. - -.. L15 -:: - - cat foo.txt | tr -d '\r' > bar.txt - -.. R16 - -The ``-c`` flag complements the first set of characters. - -.. L16 -:: - - tr -cd '[:alnum:]' - -.. R17 - -It therefore removes all non-alphanumeric characters. - -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 - -.. L17 -:: - - cat items.txt - -.. R18 - -Now, let us try and get rid of the duplicate lines from this file using -the ``uniq`` command. - -.. L18 -:: - - uniq items.txt - -.. 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. - -.. L19 -:: - - sort items.txt | uniq - -.. 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. - -.. L20 -:: - - uniq -u items-sorted.txt - -.. R21 - -The ``-c`` option displays the number of times each line occurs in the file. - -.. L21 -:: - - uniq -dc items-sorted.txt - -.. L22 - -{{{ Show summary 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. - -.. L23 - -{{{ Show self assessment questions slide }}} - -.. R23 - -Here are some self assessment questions for you to solve - - 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. - -.. L24 - -{{{ Solution of self assessment questions on 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. - -.. L25 - -{{{ Show the Thank you slide }}} - -.. R25 - -Hope you have enjoyed this tutorial and found it useful. -Thank you! |