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

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