Difference between revisions of "BASH/C3/More-on-functions/English-timed"
From Script | Spoken-Tutorial
Sandhya.np14 (Talk | contribs) |
|||
(3 intermediate revisions by 2 users not shown) | |||
Line 14: | Line 14: | ||
|- | |- | ||
|00:09 | |00:09 | ||
− | | | + | | To pass an '''argument''' to a '''function'''; |
|- | |- | ||
|00:11 | |00:11 | ||
− | | | + | | To define '''local variable''' within a '''function''' and |
|- | |- | ||
| 00:16 | | 00:16 | ||
− | | | + | | To define '''global variable''' in a '''function''' |
|- | |- | ||
Line 42: | Line 42: | ||
|- | |- | ||
|00:37 | |00:37 | ||
− | | | + | | '''Ubuntu Linux''' 12.04 '''Operating System''' |
|- | |- | ||
|00:42 | |00:42 | ||
− | | | + | | '''GNU BASH''' version 4.2. |
|- | |- | ||
Line 94: | Line 94: | ||
|- | |- | ||
|01:49 | |01:49 | ||
− | | In a similar manner, I will '''call''' the same '''function''' with a different set of '''arguments'''. So, I have'''say_welcome''' space within double quotes '''functions in''' space within double quotes '''Bash'''. | + | | In a similar manner, I will '''call''' the same '''function''' with a different set of '''arguments'''. So, I have''' say_welcome''' space within double quotes '''functions in''' space within double quotes '''Bash'''. |
|- | |- | ||
Line 138: | Line 138: | ||
|- | |- | ||
|03:03 | |03:03 | ||
− | | | + | |Its value will be valid within the '''function''' in which it is defined. |
|- | |- | ||
|03:10 | |03:10 | ||
− | | | + | | '''Local variables''' are declared using keyword '''local'''. |
|- | |- | ||
Line 194: | Line 194: | ||
|- | |- | ||
|04:14 | |04:14 | ||
− | |'''middle_name ''' | + | |'''middle_name ''' and '''last_name'''. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
Line 222: | Line 218: | ||
|- | |- | ||
|04:45 | |04:45 | ||
− | | '''$first_name, ''' | + | | '''$first_name, ''''''$middle_name '''and '''$last_name'''. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
Line 253: | Line 245: | ||
|- | |- | ||
− | |||
|05:18 | |05:18 | ||
| The first line of output displays the message '''"Hello Pratik K Patil".''' | | The first line of output displays the message '''"Hello Pratik K Patil".''' | ||
Line 295: | Line 286: | ||
|- | |- | ||
|06:07 | |06:07 | ||
− | | | + | |To pass '''arguments''' to a''' function'''; |
− | + | To declare '''local variable '''in a '''function'''; | |
|- | |- | ||
|06:14 | |06:14 | ||
− | | | + | |To declare '''global variable '''in a '''function''' with the help of a few examples. |
|- | |- | ||
Line 308: | Line 299: | ||
|- | |- | ||
|06:22 | |06:22 | ||
− | |write a program | + | |write a program where the '''function''' accepts two '''arguments'''. The '''function''' should multiply the two '''arguments'''. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
Line 329: | Line 316: | ||
| 06:51 | | 06:51 | ||
| The Spoken Tutorial Project team: | | The Spoken Tutorial Project team: | ||
− | + | Conducts workshops using spoken tutorials; | |
− | + | Gives certificates to those who pass an online test. | |
|- | |- |
Latest revision as of 17:09, 23 March 2017
Time | Narration |
00:01 | Welcome to the spoken tutorial on More on functions. |
00:06 | In this tutorial, we will learn: |
00:09 | To pass an argument to a function; |
00:11 | To define local variable within a function and |
00:16 | To define global variable in a function |
00:19 | with the help of some examples. |
00:23 | 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) |
00:35 | For this tutorial, I am using: |
00:37 | Ubuntu Linux 12.04 Operating System |
00:42 | GNU BASH version 4.2. |
00:45 | Please note, GNU Bash version 4 or above is recommended to practice this tutorial. |
00:52 | Let us first learn how to pass an argument to a function and its usage. |
00:59 | Let me open a file 'function_(underscore) parameters.sh' . |
01:05 | This is the shebang line. |
01:08 | Our function name is say_(underscore)welcome. |
01:13 | Open curly bracket opens the function definition. |
01:18 | '$1' (Dollar one) is the first positional parameter. |
01:22 | '$2' (Dollar two) is the second positional parameter. |
01:26 | Close curly bracket closes the function definition. |
01:30 | Here, the function 'say_welcome' is called with arguments. |
01:35 | The syntax is- function name i.e. "say_welcome" followed by the arguments within double quotes, i.e. "Bash" and "learning". |
01:49 | In a similar manner, I will call the same function with a different set of arguments. So, I have say_welcome space within double quotes functions in space within double quotes Bash. |
02:05 | Save the file and go to the terminal. |
02:08 | Type: chmod space plus x space function underscore parameters dot sh. |
02:17 | Press Enter. |
02:19 | Type: dot slash function underscore parameters dot sh. |
02:26 | Press Enter. |
02:28 | We see that the positional parameters were substituted by the arguments passed to a function. |
02:36 | Dollar 1 ($1) was substituted by the string "Bash" and Dollar 2 ($2) with "learning". |
02:45 | Then again, Dollar 1 ($1) was substituted by "functions in" and Dollar 2 ($2) with "Bash". |
02:55 | In Bash, variables can be declared as local variables and global variables. |
03:01 | Local variable: |
03:03 | Its value will be valid within the function in which it is defined. |
03:10 | Local variables are declared using keyword local. |
03:15 | Global variable: |
03:17 | The value of a global variable can be accessed throughout a Bash script. |
03:24 | Let us learn these 2 ways to declare a variable within a function. |
03:29 | Let me open a file named 'function_(underscore)local.sh'. |
03:35 | This is the shebang line. |
03:39 | Function name is say_(underscore) hello. |
03:43 | Here, variable first_name is declared with keyword local |
03:49 | which means its value will be valid within the function say_hello only. |
03:55 | A variable declared without any keyword is treated as a global variable. |
04:01 | So, the variable last_name can be accessed throughout the script. |
04:08 | In this echo line, we will display the value of variables |
04:12 | first_name, |
04:14 | middle_name and last_name. |
04:17 | After this, we close the function. |
04:21 | Now, here, the variable middle_name is declared without keyword. So, its value will be global throughout the script. |
04:30 | Once again, we call the function here. |
04:34 | We pass two arguments to this function call namely- “Pratik” and “Patil”. |
04:41 | These echo statements will display the value of variables- |
04:45 | $first_name, '$middle_name and $last_name'. |
04:51 | Please keep in mind that variable first_name is a local variable. |
04:57 | Save the file and go to the terminal. |
05:00 | Type: chmod space plus x space function underscore local dot sh. |
05:09 | Press Enter. |
05:11 | Type: dot slash function underscore local dot sh |
05:16 | Press Enter. |
05:18 | The first line of output displays the message "Hello Pratik K Patil". |
05:25 | Here, the variable first_name that contains value "Pratik" is local |
05:31 | which means the value is limited to the function. |
05:35 | Now, let us see how the local variable behaves outside the function. |
05:41 | Here, nothing is displayed in first_name. |
05:44 | This is because the value of first_name is local to the function. And it is not available outside the function. |
05:53 | middle_name and last_name are printed as they are global variables. |
05:59 | Hope the difference is clear to you. |
06:02 | Let us now summarize. |
06:04 | In this tutorial, we learned: |
06:07 | To pass arguments to a function;
To declare local variable in a function; |
06:14 | To declare global variable in a function with the help of a few examples. |
06:20 | As an assignment- |
06:22 | write a program where the function accepts two arguments. The function should multiply the two arguments. |
06:31 | Make 3 function calls with arguments (1, 2), (2, 3) and (3, 4). |
06:39 | Watch the video available at the link shown below. |
06:43 | It summarizes the Spoken-Tutorial project. If you do not have good bandwidth, you can download and watch it. |
06:51 | The Spoken Tutorial Project team:
Conducts workshops using spoken tutorials; Gives certificates to those who pass an online test. |
07:00 | For more details, please write to contact@spoken-tutorial.org |
07:07 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
07:11 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this mission is available at: http://spoken-tutorial.org/NMEICT-Intro |
07:26 | The script has been contributed by FOSSEE and Spoken-Tutorial teams. |
07:31 | This is Ashwini Patil from IIT Bombay, signing off. Thank you for joining. |