View source for Sed-Stream-Editor/C3/Advanced-Sed-Command/English



{| border="1"
|-
|| '''VISUAL CUE'''
|| '''NARRATION'''
|-
|| '''Slide 1:'''
||Welcome to the spoken tutorial''' '''on '''Advanced''' '''Sed Command.'''
|-
|| '''Slide 2:'''

'''Learning Objectives'''
||In this tutorial,we will learn how '''sed commands''' can be used by 
* '''Programmers''' and
* '''System Administrators'''
|-
|| '''Slide 3:'''

'''System requirements'''
||This tutorial is recorded using
* '''Ubuntu Linux '''OS version 18.04 and
* '''gedit''' text editor

However, you can use any other editor of your choice.
|-
|| '''Slide 4:'''

'''Prerequisites'''
|| To follow this tutorial, you should know basics of
* '''Linux'''
* '''C programming'''
* '''Python programming''' and
* '''Bash shell script'''

If not, for relevant tutorials please visit our website.
|-
|| '''Slide 5:'''

'''Code files '''
||
*The files used in this tutorial are available in the '''Code Files '''link on this tutorial page.
* Please download and extract them
* Make a copy and then use them while practising

|-
|| '''Open the terminal'''

|| Open the '''terminal''' by pressing'''Ctrl+Alt+T''' keys simultaneously.

Please remember to press the '''Enter''' key after typing every '''command'''.
|-
|| 
|| First we will see how the '''sed commands''' are useful with '''C source code'''
|-
|| '''Go to Downloads folder'''

'''Open the two c Programs in gedit text editor'''

'''Scroll down and show the content of the file and highlight the functions'''

|| In the '''Downloads''' folder, I have saved two '''C programs''' inside the''' C_Files '''folder.

Let us open these '''program files''' in the '''text editor'''.

I’ll show how to print only the '''function''' names in the '''program''' using '''sed command'''.

Close the file.
|-
|| 
|| Switch back to the '''terminal'''.
|-
|| '''> cd Downloads/C_Files'''

'''find -name "*.c" -print -exec sed -n '/(.*);/p' {} \;'''

'''highlight find -name "*.c" 
|| Go to the folder where you have saved the''' C_Files '''directory.

Type the '''command''' as shown.

This '''find command''' will search for all filenames with''' .c extension'''
|-
|| 

'''Highlight /(.*);/'''
|| Then it will find all the '''function''' names used in these '''C programs''' inside the''' C_Files''' folder.

It will match the open and close brackets with any '''string parameter'''. 

It will also match the '''semicolons''' at the end''' '''which indicates the end of the '''statement.'''
|-
|| '''Show the output'''
|| The output prints all the '''function''' names from both the''' C program files'''.
|-
|| '''> cat Primenumber.c'''
'''Highlight n1 and n2 '''
|| Next, let us see the '''source code''' of '''Primenumber.c '''using the '''cat command'''.

What if we wish to change the '''variable''' name in the '''source code'''?

For example-

Let us change the '''variable n1''' to '''number1 '''and''' n2 '''to''' number2''' in this '''program'''.
|-
|| '''sed -e 's/n1/number1/g' -e 's/n2/number2/g' Primenumber.c'''
|| Type the '''command''' as shown.

|-
|| '''Highlight number1, number2 in the output'''

'''(int number1, number2…)'''
|| Observe the output.

With a single '''command''', the '''programmers''' can make changes in the '''function''' name or '''variable''' name.
|-
|| '''Python source code'''
|| Next let’s see how '''sed commands''' are used with '''Python program files'''.
|-
|| Go to '''Downloads''' folder and point to '''Python_ProjectFiles'''

'''Open the folder and show the files.'''
|| I have saved a sample '''Python_ProjectFiles''' directory inside the '''Downloads''' folder.

It has three '''Python program files'''.
|-
|| '''Open the three files and arrange it in the same window'''

'''Press CTRL +F and type ConnectionDatabase'''

'''and highlight ConnectionDatabase'''
|| Let us see the source code of these '''files'''.

First I will search for the word “'''ConnectionDatabase'''” in all these '''files'''.

I wish to replace “'''DatabaseConnection”''' instead of''' “ConnectionDatabase” '''in all occurrences.

Let us see how to do this using '''sed'''.
|-
|| 

'''Type'''

'''cd ..'''
'''>cd Python_ProjectFile'''
|| Switch back to '''terminal'''.

Go to the folder where the '''Python programs''' are saved on your machine.
|-
||'''sed -n '/ConnectionDatabase/p' *.py'''
|| Type the '''command''' as shown to search '''ConnectionDatabase '''in all the '''Python files'''.
|-
|| '''Highlight the output'''
||The above '''command''' will show the lines where ''''ConnectionDatabase'''' is present.

But it does not show the filename.
|-
||'''find -name "*.py" -print -exec sed -n '/ConnectionDatabase/p' {} \;'''

'''Highlight find and sed'''

'''Highlight'''
'''find -name "*.py" -print -exec '''
'''Highlight'''
'''sed -n '/ConnectionDatabase/p' {} \;'''
|| Now type this '''command''' on the '''terminal'''.
This will fetchthe filename followed by the matched '''pattern'''within that file.

Here we have combined the '''find unix command''' and '''sed command'''.

This '''find command'''will find all the filenames with '''.py extension.'''

Then it will print the filenames on the '''terminal''' and provide the input to the '''sed command'''.

Finally the '''sed command''' processes the file based on the '''pattern''' we specified.
|-
|| '''Highlight the output'''
||Now we see the information about the filename and matched '''pattern''' in that file.
|-
|| 
||Next, we will search "'''ConnectionDatabase'''" and replace it with "'''DatabaseConnection'''".
|-
||'''find -name "*.py" -print -exec sed -n 's/ConnectionDatabase/DatabaseConnection/gp' {} \;'''

|| For that, type the '''command''' as shown.

We have successfully replaced the word '''ConnectionDatabase''' with '''  DatabaseConnection.'''
|-
|| '''Highlight the output in the terminal window'''
|| However, the output has not been saved into any file.

It is just displayed on the '''terminal'''.
|-
||'''find -name "*.py" -print -exec sed -i's/ConnectionDatabase/DatabaseConnection/g' {} \;'''

||To make changes in the original file,''' '''type the same '''command''' with '''-i, '''as shown.

This '''command''' will make the replacement changes in the '''Python files'''.

Let us cross-check the changes in the files.
|-
|| '''In downloads, go to the folder Python_ProjectFile'''

'''Open the file with .py extension and highlight the replaced string'''
|| Go to the folder '''Python_ProjectFiles.'''

Open the '''Python source code''' in the '''text editor'''.

We can see that we have successfully replaced the '''string''' in the '''.py files'''.

This feature is very helpful for '''programmers''' to replace certain '''code''' in the entire project file.
|-
|| '''Bash'''
|| Next we will see how '''sed commands''' are used in '''Bash shell scripts'''.
|-
|| '''Slide 6: '''

'''Linux - System Administrators'''
|| Let us see an example of how '''System Administrators''' manage the '''configuration files''' on the '''server'''.

'''System Administrators''' mostly work with configuration files for multiple sites.
|-
|| '''Slide 7:'''

'''Example'''
|| As an example, we will learn to create a separate '''apache config''' file for a list of '''websites'''. 

For this, we need to have two files
#A template of '''apache''' '''config '''and
#A list of '''website''' names

We can do this task using only a single one line '''command'''.

Or we can do this by copying a file and changing the '''website''' name at each place in the '''config file'''.
|-
|| 
|| Let us learn how to do this task.
|-
|| '''Go to the Downloads folder.'''

'''Locate BASH_Example'''

'''Point to 000-default.conf '''and '''website_list.'''

'''open 000-default.conf in gedit'''

'''open websitelist in gedit'''

'''Point to sitefiles folder'''
|| Go to the '''Downloads '''folder.

Here I have saved a '''BASH_Example''' directory.

Inside this, I have saved two '''text files''' named '''000-default.conf '''and '''websitelist.'''

Let us open '''000-default.conf'''. This is the template of '''apache config''' file.

'''websitelist '''contains the list of '''site '''names. We have 3 '''website '''names here.

There is''' '''another empty folder named as''' sitefiles '''where the output will get stored.

Here a separate '''config file''' will be created for each '''website''' with the necessary changes in the file.
|-
|| '''Type'''

'''>cd ..'''

'''> cd Bash_Example '''

|| Let us see the command to do this. 

Switch back to the '''terminal'''.

Go to the folder '''Bash_Example '''where the required files are saved.
|-
|| '''for i in $(cat websitelist); do sed "s/localhost/$i/" 000-default.conf > sitefiles/$i.conf; done'''

<div style="color:#000000;">'''Highlight for i in $(cat websitelist)'''

<div style="color:#000000;">'''Highlight sed "s/localhost/$i/" 000-default.conf'''

<div style="color:#000000;">'''Highlight > sitefiles/$i.conf; done'''

|| Type the '''for loop command '''as shown and press '''Enter'''.

In this '''Bash script, '''the '''for loop''' is used for fetching all the '''site '''names from the '''websitelist''' file.

Next we are replacing it with '''localhost''' in the file '''000-default.conf'''

Then we are storing the output of the '''sed command''' in a separate file within '''sitefiles''' folder.

Each file is saved with a specific '''site '''name and '''.conf extension'''.
|-
|| Go to the '''sitefiles''' folder.

Point to the three files.

Open a file and highlight 
|| Let us now check the output.

Go to the '''sitefiles''' folder. We can see three separate '''config''' files, as expected.

Open each file and check the replacement in the place of '''localhost'''.
|-
|| 
|| Understanding '''sed commands''' will surely make the '''System Administrator's '''daily task easy. 
|-
|| '''Slide 9:'''

'''Summary'''
|| With this we come to the end of this tutorial. Let us summarize.
|-
|| 
|| In this tutorial, we learnt how '''sed commands''' can be used by *'''Programmers''' and
*'''System Administrators'''
|-
|| '''Slide 8:'''

'''Assignment:'''
|| As an assignment do the following
#Change the content of '''websitelist '''file for the below '''Google products'''.

**'''google.com'''
**'''drive.google.com'''
**'''meet.google.com'''

#Execute the''' for loop command''' as explained in the tutorial.
#Check the output inside the '''sitefiles '''folder'''.'''
|-
|| '''Slide 10:'''

'''(About Spoken Tutorial Project)'''
|| The video at the following link, summarizes the''' Spoken Tutorial '''project.

Please download and watch it.
|-
|| '''Slide 11:'''

'''(About Spoken Tutorial Project)'''
|| The '''Spoken Tutorial''' Project Team conducts workshops and gives certificates.

For more details, please write to us.
|-
|| '''Slide 12:'''

'''Forum questions:'''
|| Please post your timed queries on this forum.
|-
||'''Slide 13: Acknowledgement'''

|| Spoken Tutorial project is funded by the Ministry of Education (MoE), Govt. of India.

|-
|| 
||This is Pooja from Spoken Tutorial project signing off.

Thanks for joining.
|-
|}