Difference between revisions of "BASH/C3/Basics-of-Redirection-(error-handling)/English-timed"
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| 00:01 | | 00:01 | ||
| − | | Dear friends, welcome to the spoken tutorial on''' Basics of redirection''' | + | | Dear friends, welcome to the '''spoken tutorial''' on''' Basics of redirection'''. |
|- | |- | ||
| 00:07 | | 00:07 | ||
| − | | In this tutorial, we will learn | + | | In this tutorial, we will learn: |
|- | |- | ||
| 00:10 | | 00:10 | ||
| − | |Input and output in '''Bash''' | + | |* Input and output in '''Bash''' |
|- | |- | ||
| 00:12 | | 00:12 | ||
| − | | Redirection and file descriptors | + | |* Redirection and file descriptors |
|- | |- | ||
| 00:15 | | 00:15 | ||
| − | |Standard input | + | |* Standard input |
|- | |- | ||
| 00:16 | | 00:16 | ||
| − | | Standard output | + | |* Standard output |
|- | |- | ||
| 00:18 | | 00:18 | ||
| − | | Standard error | + | |* Standard error |
|- | |- | ||
| 00:19 | | 00:19 | ||
| − | | | + | |with the help of some examples. |
|- | |- | ||
| 00:22 | | 00:22 | ||
| − | | To follow this tutorial you should have knowledge of '''Shell Scripting''' in''' BASH.''' | + | | To follow this tutorial, you should have knowledge of '''Shell Scripting''' in''' BASH.''' |
|- | |- | ||
| 00:28 | | 00:28 | ||
| − | |If not, for relevant tutorials please visit our website which is as shown | + | |If not, for relevant tutorials, please visit our website which is as shown. '''(http://www.spoken-tutorial.org)''' |
|- | |- | ||
| 00:34 | | 00:34 | ||
| − | | For this tutorial I am using | + | | For this tutorial, I am using |
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| 00:43 | | 00:43 | ||
| − | |Please note,''' GNU Bash | + | |Please note,''' GNU Bash''' version 4 or above is recommended for practice. |
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| 00:50 | | 00:50 | ||
| − | | In '''GNU/Linux '''we can send output to a file or read input from a file. | + | | In '''GNU/Linux '''we can send '''output''' to a file or read '''input''' from a file. |
|- | |- | ||
| 00:58 | | 00:58 | ||
| − | | Each '''Shell''' command has its own inputs and outputs | + | | Each '''Shell''' '''command''' has its own inputs and outputs. |
|- | |- | ||
| 01:03 | | 01:03 | ||
| − | |Input and output is redirected using a special notation interpreted by the '''Shell''' | + | |Input and output is redirected using a special notation interpreted by the '''Shell'''. |
|- | |- | ||
| 01:11 | | 01:11 | ||
| − | | Changing the default path of input or output is called as''' redirection''' | + | | Changing the default path of input or output is called as''' redirection'''. |
|- | |- | ||
| 01:18 | | 01:18 | ||
| − | | In GNU/Linux everything is a file, including the hardware | + | | In GNU/Linux everything is a file, including the hardware. |
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| Line 92: | Line 92: | ||
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| 01:27 | | 01:27 | ||
| − | | '''0''' for '''Input''' i.e. '''Keyboard''' | + | |* '''0''' for '''Input''' i.e. '''Keyboard''' |
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| 01:31 | | 01:31 | ||
| − | | '''1''' for '''Output''' i.e. '''Screen ''' | + | |* '''1''' for '''Output''' i.e. '''Screen ''' |
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| 01:34 | | 01:34 | ||
| − | | '''2 '''for '''Error '''i.e. '''Screen ''' | + | |* '''2 '''for '''Error '''i.e. '''Screen. ''' |
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| 01:46 | | 01:46 | ||
| − | | A | + | | A re-director uses '''POSIX''' numbers to talk with a user or other program. |
|- | |- | ||
| 01:54 | | 01:54 | ||
| − | | Standard input: Standard input is the default input method | + | | '''Standard input''': Standard input is the default input method. |
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| 02:07 | | 02:07 | ||
| − | | Also known as '''stdinb(Standard input). ''' | + | | Also known as '''stdinb (Standard input).''' |
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| 02:13 | | 02:13 | ||
| − | | The default standard input is the keyboard. | + | | The default '''standard input''' is the keyboard. |
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| 02:17 | | 02:17 | ||
| − | | | + | | '''Less than '''symbol is '''input redirection''' symbol. |
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| 02:22 | | 02:22 | ||
| − | | The syntax is ''' | + | | The syntax is- '''command''' space less than symbol space '''filename''' |
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| 02:30 | | 02:30 | ||
| − | | Let me open a file named '''redirection dot sh''' | + | | Let me open a file named '''redirection dot sh'''. |
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| 02:34 | | 02:34 | ||
| − | | I have typed some code in this file. | + | | I have typed some '''code''' in this file. |
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| Line 152: | Line 152: | ||
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| 02:41 | | 02:41 | ||
| − | | Type''' sort space less than symbol space file dot txt'' | + | | Type: ''' sort''' space less than symbol space '''file dot txt''. |
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| 02:48 | | 02:48 | ||
| − | | This is an example of input redirection. | + | | This is an example of '''input redirection'''. |
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| 02:52 | | 02:52 | ||
| − | | The input is taken from file '''file dot txt''' | + | | The '''input''' is taken from file '''file dot txt'''. |
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| 02:57 | | 02:57 | ||
| − | | '''sort '''command does the '''sorting '''of numbers present in ''' file dot txt''' | + | | '''sort '''command does the '''sorting '''of numbers present in ''' file dot txt'''. |
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|03:04 | |03:04 | ||
| − | |Click on '''Save''' | + | |Click on '''Save'''. |
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|03:06 | |03:06 | ||
| − | | Let us run the file ''' redirection dot sh''' | + | | Let us '''run''' the file ''' redirection dot sh'''. |
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|03:18 | |03:18 | ||
| − | | Before that, let us see the content of '''file dot txt''' | + | | Before that, let us see the content of '''file dot txt'''. |
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| 03:23 | | 03:23 | ||
| − | | Type '''cat space file dot txt'''. | + | | Type: '''cat space file dot txt'''. |
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| 03:27 | | 03:27 | ||
| − | |Press Enter | + | |Press '''Enter'''. |
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| 03:30 | | 03:30 | ||
| − | |You can see that the file contains series of numbers | + | |You can see that the file contains series of numbers. |
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| 03:45 | | 03:45 | ||
| − | | Type '''dot slash redirection dot sh''' | + | | Type: '''dot slash redirection dot sh''' |
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|03:51 | |03:51 | ||
| − | | We can see the output on the '''terminal''' after sorting. | + | | We can see the '''output''' on the '''terminal''' after sorting. |
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| 04:00 | | 04:00 | ||
| − | | Come back to our slides. | + | | Come back to our '''slides'''. |
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| 04:03 | | 04:03 | ||
| − | | Standard output: Standard output is used by all commands to display output. | + | | '''Standard output''': Standard output is used by all commands to display output. |
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Revision as of 09:12, 7 July 2015
Title of script: Basics of redirection
Author: Lavitha Pereira
Keywords: Video tutorial, redirection, file descriptors, standard input, standard output, standard error
| Time | Narration |
| 00:01 | Dear friends, welcome to the spoken tutorial on Basics of redirection. |
| 00:07 | In this tutorial, we will learn: |
| 00:10 | * Input and output in Bash |
| 00:12 | * Redirection and file descriptors |
| 00:15 | * Standard input |
| 00:16 | * Standard output |
| 00:18 | * Standard error |
| 00:19 | with the help of some examples. |
| 00:22 | To follow this tutorial, you should have knowledge of Shell Scripting in BASH. |
| 00:28 | If not, for relevant tutorials, please visit our website which is as shown. (http://www.spoken-tutorial.org) |
| 00:34 | For this tutorial, I am using |
| 00:36 | Ubuntu Linux 12.04 Operating System and |
| 00:40 | GNU BASH version 4.2 |
| 00:43 | Please note, GNU Bash version 4 or above is recommended for practice. |
| 00:50 | In GNU/Linux we can send output to a file or read input from a file. |
| 00:58 | Each Shell command has its own inputs and outputs. |
| 01:03 | Input and output is redirected using a special notation interpreted by the Shell. |
| 01:11 | Changing the default path of input or output is called as redirection. |
| 01:18 | In GNU/Linux everything is a file, including the hardware. |
| 01:24 | Common return values are: |
| 01:27 | * 0 for Input i.e. Keyboard |
| 01:31 | * 1 for Output i.e. Screen |
| 01:34 | * 2 for Error i.e. Screen. |
| 01:38 | 0, 1, 2 are POSIX numbers and also known as file descriptors' (FD). |
| 01:46 | A re-director uses POSIX numbers to talk with a user or other program. |
| 01:54 | Standard input: Standard input is the default input method. |
| 02:00 | It is used by all commands to read input. |
| 02:04 | It is denoted by zero (0). |
| 02:07 | Also known as stdinb (Standard input). |
| 02:13 | The default standard input is the keyboard. |
| 02:17 | Less than symbol is input redirection symbol. |
| 02:22 | The syntax is- command space less than symbol space filename |
| 02:30 | Let me open a file named redirection dot sh. |
| 02:34 | I have typed some code in this file. |
| 02:37 | This is the shebang line. |
| 02:41 | Type: sort' space less than symbol space file dot txt. |
| 02:48 | This is an example of input redirection. |
| 02:52 | The input is taken from file file dot txt. |
| 02:57 | sort command does the sorting of numbers present in file dot txt. |
| 03:04 | Click on Save. |
| 03:06 | Let us run the file redirection dot sh. |
| 03:10 | Open the terminal using Ctrl, Alt and T simultaneously on your keyboard. |
| 03:18 | Before that, let us see the content of file dot txt. |
| 03:23 | Type: cat space file dot txt. |
| 03:27 | Press Enter. |
| 03:30 | You can see that the file contains series of numbers. |
| 03:35 | Now type: chmod space plus x space redirection dot sh |
| 03:43 | Press Enter. |
| 03:45 | Type: dot slash redirection dot sh |
| 03:48 | Press Enter. |
| 03:51 | We can see the output on the terminal after sorting. |
| 03:56 | The numbers are sorted in ascending order. |
| 04:00 | Come back to our slides. |
| 04:03 | Standard output: Standard output is used by all commands to display output. |
| 04:10 | The default output is displayed on the screen. |
| 04:14 | It is denoted by number one (1). |
| 04:17 | Also known as stdout (Standard output). |
| 04:23 | ( > )Greater than symbol is the output redirection symbol |
| 04:28 | Syntax is Command space greater symbol space filename |
| 04:35 | Let me go back to a file redirection dot sh |
| 04:41 | Comment the previous line ie. sort |
| 04:45 | Below it, type ls space greater than space ls underscore file.txt |
| 04:55 | This is an example of output redirection. |
| 04:59 | The output of 'ls' will be stored in ls_file dot txt . |
| 05:06 | ls command lists the information about files in that particular directory. |
| 05:14 | Now, save the file and switch to the terminal |
| 05:19 | Let me clear the prompt. First let us type 'ls' and see the output. |
| 05:28 | Now press the uparrow key thrice. |
| 05:33 | Recall the previous command dot slash redirection dot sh. |
| 05:38 | And Press Enter. |
| 05:41 | Now let us check whether the output is redirected correctly. |
| 05:46 | Type gedit space ls underscore file dot txt and press Enter. |
| 05:56 | We can now see the output in this file. So our redirect was successful. |
| 06:03 | Come back to our slides. |
| 06:06 | Standard error is the default output error |
| 06:12 | It is used to write all system errors |
| 06:16 | It is denoted by number two (2). |
| 06:20 | Also known as stderr (Standard error). |
| 06:25 | The default standard error output is visible on the screen or monitor. |
| 06:32 | Two greater than symbol (2>) is error redirection symbol |
| 06:36 | Syntax is command space 2 greater than space error dot txt |
| 06:44 | Let me go back to the file redirection dot sh |
| 06:49 | We will comment the previous line. i.e.ls |
| 06:54 | Below it type rm space backslash tmp backslash 4815 dot txt space 2 greater than symbol space error dot txt. |
| 07:11 | The error output is redirected to error dot txt file. |
| 07:17 | Now, Click on Save and switch to the terminal. |
| 07:22 | We will type a command to see the error first. |
| 07:26 | Type rm space backslash tmp backslash 4815 dot txt |
| 07:36 | Press Enter. |
| 07:38 | The error displayed is |
| 07:40 | rm: cannot remove slash tmp slash 4815 dot txt: No such file or directory |
| 07:49 | Now we will execute our file. |
| 07:53 | Press the uparrow key. |
| 07:55 | And, Recall the previous command dot slash redirection dot sh |
| 08:01 | Press Enter. |
| 08:03 | Now let us check whether the error is redirected. |
| 08:07 | Type gedit space error dot txt and press Enter. |
| 08:15 | We can now see the error redirected to file error dot txt. |
| 08:22 | This brings us to the end of this tutorial. |
| 08:26 | Let us summarise. |
| 08:28 | In this tutorial we learnt |
| 08:31 | Input and output in Bash |
| 08:35 | Redirection and file descriptors |
| 08:38 | Standard input using <(less than) symbol |
| 08:42 | Standard output using >(greater than) symbol |
| 08:47 | Standard error using 2> (2 greater than symbol) |
| 08:52 | As an assignment, |
| 08:54 | Write a program in any language like C, C++, Java. |
| 08:59 | And redirect the output or error to a new file. |
| 09:04 | Or, create a text file with some content like your name, address. |
| 09:11 | Redirect the content to a new file. |
| 09:15 | Watch the video available at the link shown below. |
| 09:19 | It summarises the Spoken Tutorial project. |
| 09:23 | If you do not have good bandwidth, you can download and watch it. |
| 09:28 | The Spoken Tutorial Project Team |
| 09:30 | Conducts workshops using spoken tutorials |
| 09:34 | Gives certificates to those who pass an online test |
| 09:38 | For more details, please write to contact@spoken-tutorial.org |
| 09:46 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 09:50 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 09:58 | More information on this Mission is available at the link shown below. |
| 10:04 | The script has been contributed by FOSSEE and Spoken-Tutorial teams. |
| 10:10 | This is Ashwini from IIT Bombay. Signing off. Thank you for joining |
