Linux/C2/Simple-filters/English-timed

Time	Narration
0:00	Hello and welcome to the Spoken Tutorial on Simple Filters with Linux.
0:08	Here we will be learning about head, Tail, sort, cut and paste.
0:17	All these are command line text manipulation tools.
0:22	If you see a hash (#) symbol on the Terminal you need to become root to execute those commands
0:29	sudo su or su root, if you see a dollar symbol on the Terminal you can be an ordinary user to execute those commands.
0:38	I assume that you did a default installation and did not modify any path where the files are getting saved.
0:46	I am using Ubuntu 10.10 for this tutorial.
0:51	Prerequisites for this module are the ability to use the mouse , keyboard, maximize and minimize buttons on a window.
1:02	We use the Head command followed by an ascii file name, to display the first 10 lines of a file by default.
1:10	Let us create a file. I am hitting on ESC (escape) key to show this practically.
1:17	Go to Applications > Accessories > Text Editor.
1:24	I already have these numbers in another file for the sake of time constrain .
1:30	Let me copy and paste.
1:38	Hit on File , Save.
1:41	Name the file as numbers dot txt and hit on save .
1:48	Close this file.
1:53	Now go to Applications > Accessories > Terminal.
2:01	Let us try to see if we can see the file we created.
2:05	Type ls and hit on enter.
2:09	What we did here is to list all the folders and files on our home directory.
2:15	Now we can use the cat command to read the contents of the file we created.
2:21	Cat n-u-m Hit on tab to autofill the file name. Hit on Enter.
2:29	Let us do the same with head command.
2:33	Head numbers dot txt enter
2:39	Now the first 10 lines are displayed.
2:43	If we want to see the first 5 lines, use the option hyphen n5 in between the head command and the file.
2:52	Hit on Up arrow, hyphen n5 and Enter.
2:58	Now the first 5 lines alone are displayed.
3:02	Let us switch back to the presentation
3:08	F5.
3:14	The tail command works exactly opposite to the head command, it displays the last 10 lines of a file by default.
3:22	I am hitting on ALT and Tab to switch to the terminal.
3:27	tail numbers dot txt
3:31	If we want to see just the last 5 lines, use the option hyphen n5 in between the tail command and the file name.
3:40	hyphen n5 Enter
3:45	Switch to slides
3:50	A log file contains events which took place in a system.
3:55	Auth dot log file maintains log's for who logged in & who logged out.
4:01	The most useful option of the tail command is to use hyphen f option to follow the tail of a log file.
4:09	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.
4:18	Go to the terminal
4:21	tail hyphen f forward slash var log auth dot log
4:31	Let me resize this terminal
4:39	Let us open another Terminal , Application- > Accessories - > Terminal.
4:46	Let me resize this terminal
4:52	so that I can show you in a single screen how tail follows the last line in a log file.
5:00	Try to su as yourself, hit on enter.
5:05	Give in some wrong password hit on enter.
5:08	You will see that the terminal on which tail is running is appended with a new log.
5:15	The date & time specifies when the authentication failure took place.
5:23	Type date hit on enter to verify the system date and time.
5:32	Type Exit to close this terminal.
5:36	Hit CTRL C to close the running tail command & maximize the screen.
5:51	We have seen only auth dot log file in the previous example.
5:57	These are the commonly used log files in Linux.
6:01	A linux system administrator will look into these log files for more information to troubleshoot his machine if there is a problem.
6:12	Sort command as the name suggest will sort a file for us in both ascending and descending order.
6:23	sort numbers dot txt .This would sort our numbers dot txt file in ascending order.
6:31	Notice something is strange in there, sort just looks at the first character to sort, so 10,11&12 appears before the number 2.
6:43	To avoid this add the option of hyphen n, hyphen n and Enter
6:53	Now sort looks at the entire number to sort them.
6:58	To sort number dot txt in reverse order add an option of hyphen r.
7:09	We have numbers that repeat in this file, to pull out just the unique numbers add another option of hyphen u .
7:17	Go to Terminal.
7:20	Up Arrow
7:22	U enter,
7:26	Previously two 2's were displayed . Now only one 2 is displayed.
7:38	Now we will see how we can sort a file based on certain column.
7:44	Let us create a file and key in these as shown below.
7:48	Go to Applications > Accessories > Text Editor.
7:57	I already have the data in another file for the sake of time constrain let me copy & Paste the value, CTRL+C; CTRL+V.
8:11	File, Save it as marks dot txt, Hit on Save.
8:21	Don't mind the special characters on this file I don't want someone to sue me for giving them low marks
8:28	Close this file.
8:33	Let us sort based on the second column of marks dot txt file.
8:40	Go to the terminal.
8:42	sort space marks dot txt space hyphen t space open inverted commas space close inverted commas space
8:53	here hyphen t stands for the delimiter & the space in between the quotes represents it.
9:02	hyphen k2 for the second column on which sort should be performed.
9:14	Hit on Enter.
9:20	Cat marks dot txt
9:24	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.
9:43	Cut command is used to cut just certain information from a file.
9:51	Let us pull out the names from marks dot txt
9:55	Let us go to the terminal ALT Tab
9:58	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 inbetween 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 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