BOSS-Linux/C2/Simple-filters/English-timed

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Time Narration
00:02 Hello and welcome to the Spoken Tutorial on Simple Filters with Linux.
00:09 Here we will be learning about head, Tail, sort, cut and paste.
00:18 All these are command line text manipulation tools.
00:22 If you see a hash (#) symbol on the Terminal, you need to become root to execute those commands.
00:29 sudo su or su root. If you see a dollar symbol on the Terminal, you can be an ordinary user to execute those commands.
00:38 I assume that you did a default installation and did not modify any path where the files are getting saved.
00:46 I am using Linux for this tutorial.
00:51 Prerequisites for this module are- the ability to use the mouse, keyboard, maximize and minimize buttons on a window.
01:02 We use the Head command followed by an ascii file name to display the first 10 lines of a file, by default.
01:10 Let us create a file.
01:13 Go to Applications > Accessories > Text Editor.
01:20 I already have these numbers in another file for the sake of time constraint.
01:26 Let me copy and paste.
01:34 Hit on File, Save.
01:37 Name the file as numbers dot txt and hit on Save.
01:44 Close this file.
01:50 Now, go to Applications > Accessories > Terminal.
01:58 Let us try to see if we can see the file we created.
02:02 Type ls and hit on Enter.
02:05 What we did here is to list all the folders and files on our home directory.
02:11 Now we can use the cat command to read the contents of the file we created.
02:18 Cat n-u-m. Hit on tab to auto-fill the file name. Hit on Enter.
02:26 Let us do the same with the head command.
02:30 head numbers dot txt Enter.
02:36 Now the first 10 lines are displayed.
02:39 If we want to see the first 5 lines, use the option hyphen n5 in between the head command and the file name.
02:49 Hit on Up-arrow, hyphen n5 and Enter.
02:55 Now, the first 5 lines alone are displayed.
02:59 Let us switch back to the presentation.
03:04 The tail command works exactly opposite to the head command, it displays the last 10 lines of a file, by default.
03:12 I am hitting on ALT and Tab to switch to the terminal.
03:17 tail numbers dot txt
03:21 If we want to see just the last 5 lines, use the option hyphen n5 in between the tail command and the file name.
03:31 hyphen n5, Enter.
03:36 Switch to slides.
03:39 A log file contains events which took place in a system.
03:45 Auth dot log file maintains log's for who logged in & who logged out.
03:51 The most useful option of the tail command is to use hyphen f option to follow the tail of a log file.
03:59 If a new line is appended to the log file, the tail command will take that as the last line and display 10 lines, by default, above it.
04:09 Go to the terminal.
04:11 tail hyphen f forward slash var slash log slash auth dot log.
04:21 Let me resize this terminal.
04:28 Let us open another Terminal, Applications -> Accessories -> Terminal.
04:36 Let me resize this terminal
04:42 so that I can show you in a single screen how tail follows the last line in a log file.
04:50 Try to su as yourself, hit on Enter.
04:54 Give in some wrong password and hit on Enter.
04:58 You will see that the terminal on which tail is running is appended with a new log.
05:05 The date & time specify when the authentication failure took place.
05:13 Type: date, hit on Enter to verify the system date and time.
05:22 Type Exit to close this terminal.
05:26 Hit CTRL C to close the running tail command & maximize the screen.
05:42 We have seen only auth dot log file in the previous example.
05:47 These are the commonly used log files in Linux.
05:51 A Linux system administrator will look into these log files for more information to troubleshoot his machine if there is a problem.
06:02 "Sort" command, as the name suggests, will sort a file for us in both ascending and descending order.
06:13 sort numbers dot txt. This would sort our numbers dot txt file in ascending order.
06:21 Notice something is strange in there, sort just looks at the first character to sort, so 10, 11 & 12 appear before the number 2.
06:33 To avoid this, add the option of -n hyphen n and Enter.
06:43 Now, sort looks at the entire number to sort them.
06:47 To sort numbers dot txt in reverse order, add an option of hyphen r.
06:59 We have numbers that repeat in this file. To pull out just the unique numbers, add another option of hyphen u.
07:07 Go to Terminal.
07:09 Up-Arrow.
07:11 U, Enter.
07:15 Previously, two 2's were displayed. Now only one 2 is displayed.
07:28 Now, we will see how we can sort a file based on certain column.
07:33 Let us create a file and key in these as shown below.
07:38 Go to Applications > Accessories > Text Editor.
07:46 I already have the data in another file for the sake of time constraint. Let me copy & Paste the value, CTRL+C; CTRL+V.
08:01 File, Save it as marks dot txt, Hit on Save.
08:11 Don't mind the special characters on this file. I don't want someone to sue me for giving them low marks.
08:18 Close this file.
08:24 Let us sort based on the second column of marks dot txt file.
08:30 Go to the terminal.
08:32 sort space marks dot txt space hyphen t space open inverted commas space close inverted commas space.
08:43 Here, hyphen t stands for the delimiter & the space in between the quotes represents it.
08:52 hyphen k2 for the second column on which sort should be performed.
09:04 Hit on Enter.
09:10 Cat marks dot txt.
09:14 This is the original file, if you see Avir is moved above and Bala came below when we sorted based on the second column alone.
09:33 Cut command is used to cut just certain information from a file.
09:41 Let us pull out the names from marks dot txt.
09:44 Let us go to the terminal ALT Tab.
09:48 cut space marks dot txt space hyphen d space open inverted commas space close inverted commas space.
09:58 Here in cut command, 'd' is the delimiter & the space in between the quotes represents the delimiter.
10:10 hyphen f2 for the second column. Hit on Enter.
10:21 Paste command will merge corresponding subsequent lines of the files.
10:26 Let us use both, numbers dot txt and marks dot txt files now.
10:31 Go to the terminal.
10:33 paste numbers dot txt marks dot txt, Enter.
10:40 Now, the first line of marks dot txt was appended to the first line of numbers dot txt.
10:47 We can use the redirect key to redirect this output to some other file called concatefile dot txt.
10:56 Go to the terminal.
10:58 Hit on Up-arrow. Hit on the redirect key which is the Greater-than symbol. concatfile dot txt. Hit on Enter.
11:07 Cat concatfile dot txt.
11:12 Let us go to the slide.
11:15 If we want paste to print out the numbers serially, delimited with tab, we can use the hyphen s option.
11:25 paste hyphen s
11:29 numbers dot txt
11:33 Go to the slide. Spoken Tutorial project is a part of Talk to a Teacher project,
11:39 supported by the National Mission on Education through ICT, MHRD, Government of India.
11:45 For more information, you can refer to the following link.
11:48 This is Bala. Thanks a lot for watching this video and don't forget to leave a comment.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14