BASH/C3/Basics-of-functions/English-timed
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Revision as of 14:42, 8 December 2014 by PoojaMoolya (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 underscore name |
| 01.32 | within curly brackets, |
| 01.34 | the commands to be executed |
| 01.37 | The second syntax is |
| 01.39 | function underscore name open and close round brackets |
| 01.42 | within curly barckets, |
| 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, function name is machine. |
| 02.26 | The content 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 interperter 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 learnt, |
| 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 diskspace 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 summarises 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. |
