BASH/C3/Here-document-and-Here-string/English-timed

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Time Narration
00:01 Dear friends, welcome to the spoken tutorial on HERE document and strings.
00:08 In this tutorial, we will learn about
00:11 special-purpose redirection called Here documents and Here strings
00:17 with the help of some examples.
00:20 To follow this tutorial, you should have knowledge of Shell Scripting in BASH.
00:26 If not, for relevant tutorials, please visit our website which is as shown. http://www.spoken-tutorial.org
00:32 For this tutorial, I am using:
00:34 * Ubuntu Linux 12.04 Operating System
00:39 * GNU BASH version 4.2
00:42 Please note, GNU Bash version 4 or above is recommended for practice.
00:49 Let us learn about 'Here' document.
00:52 * It is a special purpose block of text or code.
00:56 * It is a form of I/O redirect.
01:00 * It feeds a command list to an interactive program or command line.
01:06 * It can be treated as a separate file.
01:10 * It can also be treated as multiple line input redirected to a shell script.
01:17 Syntax is-
01:18 command space less than less than space HERE.
01:24 After this, on the next line, we can give the text inputs.
01:29 It can consist of any number of lines.
01:33 Here, text1, text2, textN are the text inputs.
01:40 After the text inputs, on the next line, we type the keyword HERE again.
01:46 It denotes the closing of HERE document.
01:50 Let us understand this with an example.
01:53 I will open a file named here dot sh .
01:59 The first line of code is the shebang line.
02:04 Let me put a block of code after this line.
02:09 'wc' represents word count.
02:12 wc hyphen w counts the number of words in the HERE document.
02:20 The block of code or text until the second occurrence of HERE will be treated as a file.
02:28 The content present in HERE document is an input to the command wc hyphen w.
02:36 HERE acts as a delimiter for wc hyphen w command while reading multi-line input.
02:47 If we try to execute the same command in the terminal, we should get '4' as an output.
02:55 This is because we have passed four words to the command wc hyphen w.
03:03 Now click on Save to save the file.
03:06 Let us switch to the Terminal using Ctrl, Alt and T keys simultaneously on your keyboard.
03:15 Type: chmod space plus x space here dot sh
03:22 Press Enter.
03:24 Type: dot slash here dot sh
03:27 Press Enter.
03:30 We can see the output as 4
03:33 that is, number of words in 'Here' document is 4.
03:38 Come back to our program.
03:41 Let us add two more words here, at the beginning of the text.
03:47 Hello and welcome to Bash learning.
03:52 Click on Save.
03:54 Let us execute the program again.
03:57 On the terminal, type: dot slash here dot sh
04:04 Press Enter.
04:06 Now the output is 6 because we added two more words to our text.
04:13 We can also pass an argument to the Here document.
04:18 Let us see how to do this with an example.
04:22 Let me open a file named hereoutput dot sh.
04:28 The command cat will concatenate files and print the standard output.
04:35 Note that we have used the string "this" instead of "HERE".
04:41 It’s not necessary that you always have to use the delimiter HERE.
04:47 You can use any other delimiter also.
04:51 This line will display the 0th (zeroth) argument.
04:55 The 0th (zeroth) argument, by default, is the filename.
05:00 This line will display the 1st argument passed to the program.
05:05 And this line will display the 2nd argument passed to the program.
05:09 Here we have to close the document using the same delimiter this.
05:17 Save the file. Let us now execute the program.
05:21 On the terminal, type: chmod space plus x space hereoutput dot sh.
05:29 Press Enter
05:32 Type: dot slash hereoutput dot sh space Sunday space Monday
05:40 The output is displayed as:
05:43 "0'th argument is: dot salsh hereoutput dot sh" which is the filename.
05:49 "1st argument is: Sunday"
05:51 "2nd argument is: Monday" .
05:55 Let us learn about "Here" string now.
05:59 * Here string is used for input redirection from text or a variable.
06:06 * The input is mentioned in the same line within single quotes.
06:12 The syntax is- command space three 'less than symbols' space within single quotes write string
06:22 Let us understand this with an example.
06:25 I will open the same file here dot sh.
06:30 Here at the end, I will type: wc space hyphen w three less than symbols space within single quotes Welcome to Bash learning.
06:44 This will redirect the string within quotes to the command wc hyphen w.
06:52 Now click on Save to save the changes.
06:55 We will switch to the Terminal.
06:58 Now type: dot slash here dot sh.
07:03 We can see the output as 6 and 4.
07:08 Number of words in here document is 6 and number of words in here string is 4.
07:15 Likewise, you can write your own Here strings.
07:20 This brings us to the end of this tutorial.
07:23 Let us summarize.
07:25 In this tutorial, we learnt about:
07:27 * HERE document
07:29 * HERE string.
07:31 As an assignment, convert a string to uppercase using:
07:36 * Here document
07:37 * Here string.
07:39 Hint: tr space a hyphen z space capital A hyphen capital Z.
07:47 This is the command to convert characters from lower to upper case.
07:54 Watch the video available at the link shown below.
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08:44 The script has been contributed by FOSSEE and Spoken-Tutorial teams.
08:50 This is Ashwini Patil from IIT Bombay, signing off.
08:54 Thank you for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Pratik kamble, Sandhya.np14