View source for Linux-Ubuntu/C3/Introduction-to-grep-command/English

'''Title of the Script: Introduction to grep command.

'''Author:''' EduPyramids.'''

'''Keywords:''' '''grep, pattern matching, case-insensitive, inverse match, multiword search, line numbers, count matches, edupyramids, video tutorial.'''


{|border=1
|- 
|| '''Visual Cue'''
|| '''Narration'''
|- 
|| '''Slide 1'''

'''Title Slide'''
|| Welcome to this spoken tutorial on '''Introduction to grep command'''.
|- 
|| '''Slide 2 Learning Objectives'''



|| In this tutorial, we will learn to:
* View the content of a file 
* List entries of a particular stream 
* Ignore cases while searching
* Handle lines that do not match a pattern 
* Display line numbers with the entries 
* Store the result in another file 
* Count the number of matches

|- 
|| '''Slide 3'''

'''System Requirements'''


|| To record this tutorial, I am using


'''Ubuntu OS '''version 24 point zero 4
|- 
|| '''Slide 4Pre-requisites'''

'''https://EduPyramids.org'''


|| To follow this tutorial,

Learners should have '''Ubuntu version 24 point zero 4'''.

And should be familiar with basic Linux terminal commands.

For the prerequisite Linux tutorials please visit this website.
|- 
|| '''Slide 5'''

'''Code Files'''

The following code files are required to practice this tutorial.

# '''grepdemo.txt'''
# '''igc-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.
|- 
|| 
|| First let us learn about regular expressions.
|- 
|| '''Slide 6'''

'''Regular Expressions'''
|| 
* Regular expressions are patterns used to match text.
* They help to search and filter information in files.
* They can match words, numbers, or character sequences.
* In Linux, commands like '''grep''' use regular expressions.

|- 
|| '''Slide 7'''

'''grep command '''
||
* '''grep''' is a '''Linux''' command used to search text.
* It finds lines that match a given pattern.
* It works on files or standard input.
* It supports regular expressions for searching.

|- 
|| Download code file.Cut and paste to Home directory.open '''grepdemo.txt '''code file.
|| We will now demonstrate the '''grep''' command using the '''grepdemo.txt file'''.

Download this file and move it to your home directory.
|- 
|| show the entries and point to the separation bar (|) 
|| This file contains 13 entries.Each entry has a roll number, name, stream, marks, result, and stipend. 

The fields are separated by a vertical bar, which acts as a '''delimiter'''.
|- 
|| '''Note: Please type the commands on the terminal don't paste as the double quotes are wrong.'''
|| Let us see how grep works.

Let’s find students from the computer’s stream.
|- 
|| Type

'''grep "computers" grepdemo.txt '''press enterShow side by side '''grepdemo.txt '''file entries.
|| At the terminal type, '''grep space double quote computers double quote space grepdemo dot t x t '''and press '''Enter'''. 

The output shows entries from the computer’s stream.

Let us compare it with the original file.
|- 
|| Highlight Zubin entry in the file
|| Notice that the entry for Zubin is missing.

This happens because '''grep''' is case sensitive. 
|- 
|| Point to the capital C
|| Why is this entry missing?

'''grep''' searched for computers in lowercase.

Zubin’s stream is written as Computers with a capital '''C'''.
|- 
|| Type '''grep -i "computers" grepdemo.txt '''Highlight '''-i'''press '''Enter'''
|| Pattern matching is case sensitive by default.

To make it case insensitive, we need to use the '''hyphen i '''option with '''grep'''.

Type this command and press '''Enter'''.
|- 
|| Point to the output.
|| Now, all four matching entries are displayed.

Observe that,''' grep''' lists only the lines that match a given pattern.

We can also do the reverse.
|- 
|| Type '''grep -iv "pass" grepdemo.txt '''Highlight '''-v'''press '''Enter'''

Point to the output.
|| Type this command. The '''hyphen v '''option lists the lines that do not match a pattern. 

Press '''Enter '''to see the output.

Output shows students who failed or have incomplete results.
|- 
|| Show side by side home folder.

Type '''grep -iv "pass" grepdemo.txt > notpass.txt''' press '''Enter'''.
|| Let us store the output in a file named '''not pass dot t x t'''.

Type this command and press''' Enter'''.The file is created successfully.
|- 
|| Type '''cat notpass.txt '''press '''Enter'''.
|| To view the students who have not passed, type '''cat space not pass dot t x t '''and press '''Enter'''.

Observe the output.
|- 
|| Type '''grep -i "fail" grepdemo.txt '''


Highlight''' '''output
|| Type this command to list the failed students and press '''Enter'''.

The output shows all students who have failed.
|- 
|| type

'''grep -in "fail" grepdemo.txt '''


Press Enter.
|| Let us use the '''hyphen n '''option to show line numbers with matching entries.

Type this command and press '''Enter'''.

Observe the output.
|- 
|| Type '''clear '''press''' Enter'''.
|| Let us clear the terminal screen.
|- 
|| 
|| So far, we used single-word patterns. 

For multi-word patterns, we have to put the entire pattern in quotes.
|- 
|| type

'''grep -i "ankit saraf" grepdemo.txt '''press enter
|| Type this command and press '''Enter'''.

We can see that '''Ankit Saraf''''s record is displayed.
|- 
|| At the prompt type

'''grep -i "fail" grepdemo.txt notpass.txt'''

press''' Enter'''.
|| We can also find patterns in multiple files.

Type this command and press''' Enter'''.

Observe the output.
|- 
|| Point to the output.
|| While searching for multiple files, '''grep''' shows the filename for each match.

In this example, '''grep demo dot t x t '''and '''not pass dot t x t '''are searched.
|- 
|| Show only the inside files contents of '''notpass.txt '''and '''grepdemo.txt'''
|| These are the records from '''not pass dot t x t''' file and these are the records from '''grep demo dot t x t''' file.
|- 
|| Type

'''grep -c “Fail” grepdemo.txt''' press '''Enter'''.
|| To display only the number of matches, use the '''hyphen c''' option.

Type this command and press the '''Enter '''key. Output shows the number of matches.

|-
|| '''Slide 8'''

'''Summary'''

In this tutorial, we have learnt to:
* View the content of a file 
* List entries of a particular stream 
* Ignore cases while searching
* Handle lines that do not match a pattern 
* Display line numbers with the entries 
* Store the result in another file 
* Count the number of matches

|| With this we come to the end of this tutorial.

Let us summarise.
|- 
|| '''Slide 9'''

'''Assignment'''

As an assignment,

# Use grep to find all students in the “Maths” stream in grepdemo.txt.
# List lines that do not contain civil and save to '''nonCivil.txt'''.
# Show line numbers of entries containing fail.
# Search for a multi word pattern, for example Mani Chowdhari, in '''grepdemo.txt'''.


|| 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.
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