BASH/C3/Basics-of-functions/English-timed
From Script | Spoken-Tutorial
Revision as of 10:10, 14 July 2015 by Sandhya.np14 (Talk | contribs)
| Time | Narration |
| 00.01 | Dear friends, welcome to the spoken tutorial on Basics of functions in Bash. |
| 00.08 | In this tutorial, we will learn: |
| 00.11 | * Importance of Functions |
| 00.13 | * To declare a function |
| 00.15 | * To call a function |
| 00.17 | * Work flow of a function |
| 00.19 | with the help of an example. |
| 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 Ubuntu Linux 12.04 Operating System. |
| 00.40 | Till now we were using GNU BASH version 4.1.10 |
| 00.46 | From now onwards, we will use GNU BASH version 4.2 |
| 00.52 | Please note, GNU Bash version 4 or above is recommended for practice. |
| 00.58 | Let us see what is a function and its usage. |
| 01.03 | A function is a collection of commands or an algorithm. |
| 01.08 | It is intended to do a specific task. |
| 01.12 | It is used to break-up a complex program into separate tasks. |
| 01.18 | This improves overall script readability and ease of use. |
| 01.24 | There are two syntaxes for function declaration. |
| 01.28 | First syntax is- |
| 01.29 | function space function_name |
| 01.32 | within curly brackets, |
| 01.34 | the commands to be executed. |
| 01.37 | The second syntax is- |
| 01.39 | function_name open and close round brackets |
| 01.42 | within curly brackets, |
| 01.44 | the commands to be executed. |
| 01.47 | Function call- |
| 01.48 | Function can be called anywhere within the program. |
| 01.53 | Type the function name at the location where you want to call it. |
| 01.58 | The syntax is the function_name itself. |
| 02.02 | Let us understand this with the help of a simple example. |
| 02.07 | I have already typed the code in a file function.sh. |
| 02.12 | This is the shebang line. |
| 02.14 | Function is declared by the keyword function followed by function name. |
| 02.21 | Here, the function name is machine. |
| 02.26 | The contents within curly brackets is called function definition. |
| 02.32 | I have displayed various machine details like- |
| 02.36 | uname hyphen a gives machine information. |
| 02.41 | w hyphen h gives users logged onto system. |
| 02.46 | uptime gives the time since machine was on. |
| 02.51 | free gives memory status. |
| 02.54 | df hyphen h gives filesystem status. |
| 02.57 | The main program starts here. |
| 03.01 | We display the message “Beginning of main program” . |
| 03.06 | Here, machine is a function call. |
| 03.09 | Then we display the message “End of main program”. |
| 03.13 | Let us understand the workflow. |
| 03.16 | # When the bash interpreter visits the function definition, it simply scans the function. |
| 03.23 | # The function is called only when its name appears within the script. |
| 03.28 | # When the interpreter reads the function name, it executes the function definition. |
| 03.36 | The interpreter treats function name as a command. |
| 03.41 | Please remember that we have to define the function before calling it. |
| 03.47 | Now go to the terminal. To make this code file executable, |
| 03.52 | type: chmod space plus x space function dot sh |
| 03.59 | Press Enter. |
| 04.01 | Type: dot slash function dot sh |
| 04.05 | Press Enter. |
| 04.07 | The output that is the machine details of my system are seen on the terminal. |
| 04.14 | Please Note: The output will vary from system to system. |
| 04.19 | This brings us to the end of this tutorial. |
| 04.22 | Come back to our slides. |
| 04.24 | Let us summarize. |
| 04.25 | In this tutorial, we learned: |
| 04.28 | * Importance of functions |
| 04.30 | * Function declaration |
| 04.32 | * Function call |
| 04.33 | * Work flow of function |
| 04.35 | with an example. |
| 04.37 | As an assignment- |
| 04.38 | write a program with two functions. |
| 04.42 | # The first function should display the disk-space usage in human readable form (Hint: df hyphen h). |
| 04.51 | # The second function should display filesystem usage in human readable form (Hint: du hyphen h). |
| 05.00 | Watch the video available at the link shown below. |
| 05.03 | It summarizes the Spoken-Tutorial project. |
| 05.07 | If you do not have good bandwidth, you can download and watch it. |
| 05.12 | The Spoken Tutorial Project team: Conducts workshops using spoken tutorials; |
| 05.17 | Gives certificates to those who pass an online test. |
| 05.21 | For more details, please write to contact@spoken-tutorial.org |
| 05.29 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 05.33 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 05.41 | More information on this mission is available at the link shown below: http://spoken-tutorial.org/NMEICT-Intro |
| 05.47 | The script has been contributed by FOSSEE and spoken-tutorial team. |
| 05.52 | This is Ashwini Patil from IIT Bombay, signing off. |
| 05.56 | Thank you for joining. |
