Linux-Ubuntu/C3/Text-Editing-using-sed/English

Title of script:  Text Editing using sed

Author: EduPyramids Keywords: sed, substitute, insert, delete, global substitution, g flag, case-insensitive, context addressing, Video Tutorial.

Visual Cue	Narration
Slide 1 Title Slide	Welcome to this spoken tutorial on Text Editing using sed.
Slide 2 Learning Objectives	In this tutorial, we will learn to:* Perform text substitution using sed command. Use the g flag for global substitution. Execute multiple sed commands using the hyphen e option. Apply substitution based on context. Insert and remove lines from a file. Redirect sed output to an output file.
Slide 3 System Requirements	To record this tutorial, I am using* Ubuntu OS version 24 point 04 Bash version 5 point 1 point 16;
Slide 4 Pre-requisites https://EduPyramids.org	Learners should have* Ubuntu version 24 point 04 and Bash version 5 point 1 point 16 For the prerequisite Linux tutorials please visit this website.
Slide 5 Code files The following code files are required to practice this tutorial.# seddemo.txt sed-commands.txt These files are provided in the Code Files link of this tutorial page.	The following code files are required to practice this tutorial. These files are provided in the Code Files link of this tutorial page.
	Let us run some examples of sed commands using the terminal.
Type cat seddemo.txtpress Enter Highlight the word kumar in the lines.Point to the fourth and sixth lines	Let us first view the contents of the file sed demo dot t x t. Notice the word Kumar. It appears twice in the fourth line and once in the sixth line.
Type sed 's/[kK]umar/Roy/' seddemo.txt	Let’s suppose we want to substitute Kumar with Roy. Type the following command and press Enter.
Highlight one by one sed s [kK]umar Roy forward slashes seddemo.txt	Let us understand this command. sed is the stream editor. The letter s stands for substitution. This pattern matches bothuppercase Kumar and lowercase kumar. The word Roy is the replacement text. The forward slashes separate the pattern and the replacement. The file sed demo dot txt is the input file.
Press Enter. Show the output on the terminal	In the output, the word Kumar is replaced with Roy.
Show the output on the terminal and the file seddemo.txt opened next to it Highlight 4th line of both output and in the file	But only the first occurrence of the word Kumar is replaced in each line. This happens because, by default, sed substitutes only the first match in a line. Note the substitution happens only on the terminal output. The original file sed demo dot t x t is not modified.
Slide 6 Global Substitution By default, sed replaces only the first match in each line. To replace all occurrences in a line, we use the g flag. The letter g stands for global substitution. When the g flag is used, sed searches the entire line for matches. Every matching pattern in that line is replaced. The g flag is written after the substitution command. General syntax: sed 's/pattern/replacement/g' filename	* By default, sed replaces only the first match in each line. To replace all occurrences in a line, we use the g flag. The letter g stands for global substitution. When the g flag is used, sed searches the entire line for matches. Every matching pattern in that line is replaced. The g flag is written after the substitution command. This is the general syntax.
Type sed 's/[kK]umar/Roy/g' seddemo.txt Press Enter Highlight the output	Type this command and press Enter. Output shows, both occurrences in the fourth line are replaced.
Type sed 's/kumar/Roy/Ig' seddemo.txt and press Enter.Case-insensitive matching	Type the following command and press Enter. Instead of specifying lowercase and uppercase letters using brackets, we can use the I option. The I option makes the pattern match case insensitive. Observe that the output is the same as the previous command. Both methods can be used to produce the same result.
Slide 7 Multiple Substitutions using -e sed allows performing more than one operation in a single command. The -e option is used to specify multiple sed expressions. Each -e represents one sed command. Commands are executed in the order they are written. This is useful when multiple substitutions are required on the same input.	* sed allows performing more than one operation in a single command. The hyphen e option is used to specify multiple sed expressions. Each hyphen e represents one sed command. Commands are executed in the order they are written. This is useful when multiple substitutions are required on the same input.
	Let us see how to replace electronics with electrical and civil with metallurgy.
Type sed -e 's/electronics/electrical/g' -e 's/civil/metallurgy/g' seddemo.txt	Type this command.
	Let us understand this code. hyphen e allows using more than one sed command in a single line. s slash electronics slash electrical slash g replaces all occurrences of electronics with electrical. s slash civil slash metallurgy slash g replaces all occurrences of civilwith metallurgy.
press Enter Highlight the replaced words in the output	Now, press Enter. Observe that words are replaced.
Context-Based Substitution	Let’s change the stream of Anirban from computers to mathematics.
Type sed '/Anirban/s/computers/mathematics/g' seddemo.txt	Type this command and press Enter. Observe that computers is changed to mathematics.
Deleting Lines using sed	Let us see how to remove all lines containing the word electronics. In other words, select those lines which do not have an electronics stream.
Type sed '/electronics/d' seddemo.txt > nonElectronics.txt	Type this command.
Highlight /electronics/ d seddemo.txt > nonElectronics.txt	Here, slash electronics slash is a context address that matches lines containing electronics. d means deletes the matched lines seddemo dot t x t is the input file. greater than means redirects output to a file non Electronics dot t x t is the output file. Press Enter.
Type cat nonElectronics.txt press Enter Show the output	Let us view the contents of the new file nonElectronics. The file shows only those records that are not in the electronics stream. You may wonder why substitutions are not reflected in the text file. This is because all substitution results are displayed only on the terminal. The original text file is not modified unless explicitly instructed.
Inserting Lines Using sed	Suppose we want to insert a line at the beginning of the file.
Type sed '1i Student Information' seddemo.txt	Type this command.
Highlight one by one 1 i Student Information	Here: • 1 is the line number• i is the insert command • Student Information is the text to be inserted
Press Enter. Highlight the line: Student Information	Press Enter. Output shows the line Student Information inserted at the beginning of the file.
Inserting Multiple Lines	Let us see how to insert more than one line in the file seddemo dot t x t. Student Information in the first line and 2026 in the next line.
Type sed '1i Student Information\n2026\nRecords' seddemo.txtpress Enter	Now let us type this command. Press Enter.
Point to \n	Notice backslash n between the string Information and 2026. backslash n moves to a new line and prints 2026 in the next line after Student Information. Similarly after 2026, new string Records is printed in the third line.
Slide 8 Summary In this tutorial, we have learnt to: Perform text substitution using sed command Use the g flag for global substitution Execute multiple sed commands using the -e option Apply substitution based on context Insert and remove lines from a file Redirect sed output to an output file	With this we come to the end of this tutorial. Let us summarise.
Slide 9 As an assignment please do the following:* Using sed and the file seddemo.txt, replace the word computers with computer-science. Replace electronics with ece in all occurrences. Perform both substitutions in a single command using the -e option. Delete all lines that belong to the civil department.	As an assignment, please do the following.
Slide 10 Thank you	This Spoken Tutorial is brought to you by EduPyramids Educational Services Private Limited SINE IIT Bombay.Thank you.

Contributors and Content Editors

Ketkinaina, Madhurig