Difference between revisions of "BASH/C3/Advance-topics-in-a-function/English"

Welcome to the spoken tutorial on Advance topics in function

• Source command
• how to put a function in the background
• with the help of some examples.

If not, for relevant tutorials, please visit our website which is as shown.

System requirements

• Ubuntu Linux 12.04 Operating System and
• GNU BASH version 4.2

Please note, GNU Bash version 4 or above is recommended for practice.

Source Command

• Source command is used to load a file into Shell script.
• It reads and execute commands from that file.
• It also imports code into the script.

Source Command

• This is useful when multiple scripts use a common data or a function library.

Syntax:

source <filename>

source <Path_to_file>

souce <filename> <arguments>

source path_to_file

source filename arguments

[Highlight]

source detail.sh

type,

echo "function machine is called in function.sh file"

}

I have a function “machine”.

Now type inside the function,

echo "function machine is called in function.sh file"

Click on Save.

echo “Beginning of program”

machine

echo “End of program”

Here type:

echo “Beginning of program”

Click on Save

Then type: machine

echo “End of program”

machine

echo “End of program”

machine is the function call.

This will print the message End of program

And we are calling the function here in function.sh file.

Now click on Save.

chmod +x function.sh>>

Press Enter

Press Enter.

./function.sh>>Press Enter

Press Enter.

Beginning of program

function machine is called in function.sh file

End of program

Background function

• To run a process in the background, we use & (ampersand) at the end of a function call.
• The shell forks a child process to run the command.
• The forked process will have a job number ([n]) and a PID (Process IDentifier)

{

}

This statement will find all the files with the extension .mp3

It will do so in the current working directory.

Hyphen iname is used to ignore the case.

And the result is stored in myplaylist.txt .

bg underscore function &

This is the function call.

Ampersand puts 'bg_function' in the background.

Now click on Save.

Let us execute the program.

chmod +x background.sh>>Press Enter

Type:chmod space plus x space background dot sh

Press Enter.

./background.sh>>Press Enter

Press Enter.

echo -e "Process runing in background are: \n"

type:

jobs -l

Type:

echo -e "Process runing in background are: slash n"

and jobs space hyphen l

Click on Save

Let me clear the prompt.

./background.sh>>Press Enter

[Output]

Inside bg_function

Process runing in background are:

[1]+ 5787 Running bg_function &

Last line of the code

Here, one within opening and closing square bracket is the job number.

3962 is the PID.

PID will vary accordingly.

If the function takes time to execute, it will run in the background.

And we will see the status as 'Running' .

If the function gets executed before the script, we will see the status as 'Done'.'

The output will vary from machine to machine.

This brings us to the end of this tutorial.

Come back to our slides.

Summary

Let us summarise.

In this tutorial we learnt

• Source command
• To put a function in the background
• With the help of some examples

Assignment

Write a function addnumbers to add two numbers and call the function in another file.

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

About the Spoken Tutorial Project

It summarises the Spoken Tutorial project.

If you do not have good bandwidth, you can download and watch it.

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Acknowledgement

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

This is Ashwini from IIT Bombay.

Thank you for joining.