Difference between revisions of "BASH/C3/Basics-of-Redirection-(error-handling)/English-timed"

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| 00:34
 
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| For this tutorial, I am using
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| For this tutorial, I am using  
  
 
|-
 
|-
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|-
 
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| 02:07
 
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|  Also known as '''stdinb (Standard input).'''
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|  Also known as '''stdin (Standard input).'''
  
 
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|  The default output is displayed on the screen.  
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|  The '''default output''' is displayed on the '''screen'''.  
  
 
|-
 
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|-
 
|-
 
| 04:23
 
| 04:23
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|  ( > )'''Greater than''' symbol is the output redirection symbol  
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|  ( > )'''Greater than''' symbol is the '''output redirection''' symbol.
  
 
|-
 
|-
 
| 04:28
 
| 04:28
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|  Syntax is '''Command space greater symbol space filename'''
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|  Syntax is '''command''' space greater than symbol space '''filename'''.
  
 
|-
 
|-
 
| 04:35
 
| 04:35
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| Let me go back to a file '''redirection dot sh'''
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| Let me go back to a file '''redirection dot sh'''.
  
 
|-
 
|-
 
| 04:41
 
| 04:41
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| Comment the previous line ie. '''sort'''
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| '''Comment''' the previous line i.e. '''sort'''.
  
 
|-
 
|-
 
| 04:45
 
| 04:45
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| Below it, type ''' ls space greater than space ls underscore file.txt'''
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| Below it, type: '''ls''' space greater than symbol space '''ls underscore file.txt'''
  
 
|-
 
|-
 
| 04:55
 
| 04:55
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| This is an example of output redirection.
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| This is an example of '''output redirection'''.
  
 
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| 05:14
 
| 05:14
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|Now, save the file and switch to the '''terminal'''
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|Now, '''save''' the file and switch to the '''terminal'''.
  
 
|-
 
|-
 
| 05:19
 
| 05:19
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| Let me clear the prompt.  First let us type ''''ls'''' and see the output.
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| Let me clear the '''prompt'''.  First, let us type ''''ls'''' and see the output.
  
 
|-
 
|-
 
| 05:28
 
| 05:28
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| Now press the '''uparrow''' key thrice.
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| Now press the '''up-arrow''' key thrice.
  
 
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|-
 
| 05:41
 
| 05:41
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| Now let us check whether the output is redirected correctly.
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| Now let us check whether the '''output''' is redirected correctly.
  
 
|-
 
|-
 
| 05:46
 
| 05:46
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| Type '''gedit space ls underscore file dot txt '''and press '''Enter.'''
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| Type: '''gedit space ls underscore file dot txt '''and press '''Enter.'''
  
 
|-
 
|-
 
| 05:56
 
| 05:56
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| We can now see the output in this file. So our redirect was successful.
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| We can now see the '''output''' in this file. So our '''redirect''' was successful.
  
 
|-
 
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| 06:03
 
| 06:03
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| Come back to our slides.   
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| Come back to our '''slides'''.   
  
 
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|-
 
| 07:26
 
| 07:26
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| Type '''rm space backslash tmp backslash 4815 dot txt'''
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| Type: '''rm space slash tmp slash 4815 dot txt'''
  
 
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| 07:38
 
| 07:38
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| The error displayed is
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| The '''error''' displayed is-
  
 
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| 07:40
 
| 07:40
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| '''rm: cannot remove slash tmp slash 4815 dot txt: No such file or directory'''
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| '''rm: cannot remove slash tmp slash 4815 dot txt: No such file or directory'''.
  
 
|-
 
|-
 
| 07:49
 
| 07:49
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| Now we will execute our file.
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| Now we will '''execute''' our file.
  
 
|-
 
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|  07:53
 
|  07:53
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|  Press the '''uparrow''' key.
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|  Press the '''up-arrow''' key
  
 
|-
 
|-
 
| 07:55
 
| 07:55
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| And, Recall the previous command '''dot slash redirection dot sh'''
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| and recall the previous '''command''' '''dot slash redirection dot sh'''.
  
 
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| 08:03
 
| 08:03
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| Now let us check whether the error is redirected.
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| Now let us check whether the '''error''' is redirected.
  
 
|-
 
|-
 
| 08:07
 
| 08:07
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| Type '''gedit space error dot txt''' and press '''Enter.'''
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| Type: '''gedit space error dot txt''' and press '''Enter.'''
  
 
|-
 
|-
 
| 08:15
 
| 08:15
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| We can now see the error redirected to file '''error dot txt'''.
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| We can now see the '''error''' redirected to file '''error dot txt'''.
  
 
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| 08:26
 
| 08:26
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| Let us summarise.  
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| Let us summarize.  
  
 
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| 08:28
 
| 08:28
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| In this tutorial we learnt
+
| In this tutorial, we learned:
  
 
|-
 
|-
 
| 08:31
 
| 08:31
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| Input and output in Bash
+
|* Input and output in Bash
  
 
|-
 
|-
 
| 08:35
 
| 08:35
−
| Redirection and file descriptors  
+
|* Redirection and file descriptors  
  
 
|-
 
|-
 
| 08:38
 
| 08:38
−
| Standard input using <(less than) symbol
+
|* Standard input using <(less than) symbol
  
 
|-
 
|-
 
| 08:42
 
| 08:42
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| Standard output using  >(greater than) symbol
+
|* Standard output using  >(greater than) symbol
  
 
|-
 
|-
 
| 08:47
 
| 08:47
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| Standard error using 2> (2 greater than symbol)
+
|* Standard error using 2> (2 greater than symbol).
  
 
|-
 
|-
 
| 08:52
 
| 08:52
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| As an assignment,
+
| As an assignment-
  
 
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|-
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|-
 
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| 08:59
 
| 08:59
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| And redirect the output or error to a new file.
+
| And '''redirect''' the '''output''' or '''error''' to a new file.
  
 
|-
 
|-
 
| 09:04
 
| 09:04
−
| Or, create a text file with some content like your name, address.
+
| Or, create a '''text file''' with some content like your name, address.
  
 
|-
 
|-
 
| 09:11
 
| 09:11
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| Redirect the content to a new file.
+
| '''Redirect''' the content to a new file.
  
 
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| 09:19
 
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| It summarises the Spoken Tutorial project.
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| It summarizes the Spoken-Tutorial project.
  
 
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| 09:28
 
| 09:28
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| The Spoken Tutorial Project Team
+
| The Spoken Tutorial project team:
  
 
|-
 
|-
 
| 09:30
 
| 09:30
−
|  Conducts workshops using spoken tutorials
+
|  Conducts workshops using spoken tutorials.
  
 
|-
 
|-
 
| 09:34
 
| 09:34
−
|  Gives certificates to those who pass an online test
+
|  Gives certificates to those who pass an online test.
  
 
|-
 
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| 09:46
 
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| Spoken Tutorial Project is a part of the Talk to a Teacher project.
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| '''Spoken Tutorial''' project is a part of the '''Talk to a Teacher''' project.
  
 
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| 09:58
 
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| More information on this Mission is available at the link shown below.  
+
| More information on this mission is available at the link shown below.  
  
 
|-
 
|-
 
| 10:04
 
| 10:04
−
| The script has been contributed by FOSSEE and Spoken-Tutorial teams.
+
| The '''script''' has been contributed by FOSSEE and Spoken-Tutorial teams.
  
 
|-
 
|-
 
| 10:10
 
| 10:10
−
| This is Ashwini from IIT Bombay. Signing off. Thank you for joining
+
| This is Ashwini from IIT Bombay, signing off. Thank you for joining.
  
 
|}
 
|}

Revision as of 10:11, 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 stdin (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 than symbol space filename.
04:35 Let me go back to a file redirection dot sh.
04:41 Comment the previous line i.e. sort.
04:45 Below it, type: ls space greater than symbol 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 up-arrow 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 slash tmp slash 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 up-arrow 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 summarize.
08:28 In this tutorial, we learned:
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 summarizes 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.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14

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