Linux/C2/Simple-filters/English-timed

Time	Narration
00:00	Hello and welcome to the Spoken Tutorial on Simple Filters with Linux.
00:08	Here we will be learning about head, Tail, sort, cut and paste.
00:17	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 Ubuntu 10.10 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. I am hitting on Esc (escape) key to show this practically.
01:17	Go to Applications > Accessories > Text Editor.
01:24	I already have these numbers in another file for the sake of time constrain.
01:30	Let me copy and paste.
01:38	Hit on File , Save.
01:41	Name the file as numbers dot txt and hit on Save.
01:48	Close this file.
01:53	Now go to Applications > Accessories > Terminal.
02:01	Let us try to see if we can see the file we created.
02:05	Type ls and hit on Enter.
02:09	What we did here is to list all the folders and files on our home directory.
02:15	Now we can use the cat command to read the contents of the file we created.
02:21	Cat n-u-m Hit on tab to autofill the file name. Hit on Enter.
02:29	Let us do the same with head command.
02:33	head numbers dot txt, Enter.
02:39	Now the first 10 lines are displayed.
02:43	If we want to see the first 5 lines, use the option hyphen n5 in between the head command and the file.
02:52	Hit on Up arrow, hyphen n5 and Enter.
02:58	Now the first 5 lines alone are displayed.
03:02	Let us switch back to the presentation.
03:08	F5
03:14	The tail command works exactly opposite to the head command, it displays the last 10 lines of a file by default.
03:22	I am hitting on ALT and Tab to switch to the terminal.
03:27	tail numbers dot txt
03:31	If we want to see just the last 5 lines, use the option hyphen n5 in between the tail command and the file name.
03:40	hyphen n5, Enter.
03:45	Switch to slides.
03:50	A log file contains events which took place in a system.
03:55	Auth dot log file maintains log's for who logged in & who logged out.
04:01	The most useful option of the tail command is to use hyphen f option to follow the tail of a log file.
04:09	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.
04:18	Go to the terminal.
04:21	tail hyphen f forward slash var slash log slash auth dot log
04:31	Let me resize this terminal.
04:39	Let us open another Terminal, Application -> Accessories -> Terminal.
04:46	Let me resize this terminal.
04:52	so that I can show you in a single screen how tail follows the last line in a log file.
05:00	Try to su as yourself, hit on Enter.
05:05	Give in some wrong password hit on Enter.
05:08	You will see that the terminal on which tail is running is appended with a new log.
05:15	The date & time specifies when the authentication failure took place.
05:23	Type date, hit on Enter to verify the system date and time.
05:32	Type Exit to close this terminal.
05:36	Hit CTRL C to close the running tail command & maximize the screen.
05:51	We have seen only auth dot log file in the previous example.
05:57	These are the commonly used log files in Linux.
06:01	A Linux system administrator will look into these log files for more information to troubleshoot his machine if there is a problem.
06:12	Sort command, as the name suggests, will sort a file for us in both ascending and descending order.
06:23	sort numbers dot txt. This would sort our numbers dot txt file in ascending order.
06:31	Notice something is strange in there, sort just looks at the first character to sort, so 10,11&12 appears before the number 2.
06:43	To avoid this, add the option of hyphen n hyphen n and Enter.
06:53	Now sort looks at the entire number to sort them.
06:58	To sort number dot txt in reverse order add an option of hyphen r.
07:09	We have numbers that repeat in this file, to pull out just the unique numbers add another option of hyphen u .
07:17	Go to Terminal.
07:20	Up Arrow
07:22	U, Enter.
07:26	Previously two 2's were displayed . Now only one 2 is displayed.
07:38	Now we will see how we can sort a file based on certain column.
07:44	Let us create a file and key in these as shown below.
07:48	Go to Applications > Accessories > Text Editor.
07:57	I already have the data in another file for the sake of time constrain, let me copy & Paste the value, CTRL+C; CTRL+V.
08:11	File, Save it as marks dot txt, Hit on Save.
08:21	Don't mind the special characters on this file. I don't want someone to sue me for giving them low marks.
08:28	Close this file.
08:33	Let us sort based on the second column of marks dot txt file.
08:40	Go to the terminal.
08:42	sort space marks dot txt space hyphen t space open inverted commas space close inverted commas space
08:53	Here, hyphen t stands for the delimiter & the space in between the quotes represents it.
09:02	hyphen k2 for the second column on which sort should be performed.
09:14	Hit on Enter.
09:20	Cat marks dot txt
09:24	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.
09:43	Cut command is used to cut just certain information from a file.
09:51	Let us pull out the names from marks dot txt
09:55	Let us go to the terminal ALT Tab
09:58	cut space marks dot txt space hyphen d space open inverted commas space close inverted commas space.
10:08	Here, in cut command d is the delimiter & the space in between the quotes represents the delimiter.
10:20	hyphen f2 for the second column. Hit on Enter.
10:31	Paste command will merge corresponding subsequent lines of the files.
10:36	Let us use both the numbers dot txt and marks dot txt file now.
10:41	Go to the terminal.
10:43	Paste numbers dot txt marks dot txt, Enter.
10:50	Now the first line of marks dot txt was appended to the first line of numbers dot txt.
10:57	We can use the redirect key to redirect this output to some other file called concatefile dot txt.
11:06	Go to the terminal.
11:08	Hit on Up arrow. Hit on the redirect key which is the Greater than symbol (>) concatfile dot txt. Hit on Enter.
11:18	Cat concatfile dot txt
11:22	Let us go to the slide.
11:25	If we want paste to print out the numbers serially delimited with tab, we can use the hyphen s option.
11:34	Paste hyphen s
11:39	numbers dot txt
11:43	Go to the slide.
11:45	Spoken Tutorial project is a part of Talk to a Teacher project,
11:49	Supported by the National Mission on Education through ICT,MHRD, Government of India.
11:55	For more information you can refer to the following link.
11:59	This script has been contributed by ----------------------(name of the translator) and this is -----------------------(name of the recorder) from --------------------------(name of the place)signing off.

Contributors and Content Editors

Minal, PoojaMoolya, Pratik kamble, Sandhya.np14, Vasudeva ahitanal