BOSS-Linux/C2/Simple-filters/English-timed
From Script | Spoken-Tutorial
| 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. |
