PoojaMoolya: Created page with "'''Title of script''': The grep command '''Author : Sachin Patil and Anirban''' '''Keywords:Search,Pattern,regular expressions,extended regular expression''' {|border=1 !..."

2015-01-29T07:00:31Z

Created page with "'''Title of script''': The grep command '''Author : Sachin Patil and Anirban''' '''Keywords:Search,Pattern,regular expressions,extended regular expression''' {|border=1 !..."

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'''Title of script''': The grep command

'''Author : Sachin Patil and Anirban'''

'''Keywords:Search,Pattern,regular expressions,extended regular expression'''

{|border=1
!'''Visual Cue'''
!'''Narration'''

|-
|Display Slide 1
|Welcome to the spoken tutorial on '''grep''' command

|-
|Display Slide 2
|In this tutorial we will learn '''grep command'''.
We will do this with the help of some examples.

|-
|Display Slide 3
|To record this tutorial, I am using

*'''Linux''' '''Operating System''' and
*'''GNU BASH''' version 4.2.24

Please note,''' GNU bash''' version 4 or above is recommended to practice this tutorial.

|-
|Display Slide 4
|As prerequisites

You should know basics of '''Linux terminal'''

For relevant tutorials, please visit our website which is as shown.

|-
|
|First let us know about regular expressions.

*Regular expressions are pattern matching techniques.

*When we have to find out whether a pattern exist in a line, paragraph or a file.

For ex. If you want to search a phone number in the telephone directory

Or

To find a keyword in a paragraph or a line, we use '''grep command'''.
Let us move on to '''grep'''.

|-
|Display Slide 5
|'''grep''' searches for one or more patterns in one or more line, paragraph or a file.

If filename is not mentioned,''' grep''' search for the patterns in the standard input.

If filename is missing, '''grep''' searches for the patterns in the standard input.

|-
|Open

“'''grepdemo.txt'''<nowiki>” [</nowiki>enter]
|I will demonstrate usage of '''grep''' using a demo file called '''grepdemo.txt'''

Let us see the content of the file.

|-
|
|This is a file that has 13 entries.

Each entry has 6 fields roll number, name, stream, marks, and stipend amount.

|-
|
|The fields are separated by a bar, which is called a '''delimiter'''.

|-
|At the prompt type

'''grep “computers” grepdemo.txt'''<nowiki> [</nowiki>enter]

At the prompt, type:

'''cat grepdemo.txt'''
|Let us see how '''grep''' works.

Say we want to use '''grep command''', to see who are the students in the '''computers''' stream.

|-
|
|For this we have to open the '''terminal'''.

So press '''CTRL + ALT and T''' keys simultaneously on your keyboard.

|-
|
|Now type on the '''terminal''':

'''grep space (within double quotes) computers (after the double quotes) space grepdemo .txt'''.Press Enter

|-
|
|This would enlist those entries where stream is '''computers'''.

|-
|
|Now compare the result with the original file.

|-
|
|Come back to our text editor.

We see that the entry for ''' Zubin''' is not enlisted.

|-
|Highlight
|Why this is so?

This is because '''grep''' searched for the pattern '''“computers”''' with small '''c'''

While for '''Zubin''', the stream is “Computers” with a capital '''C'''.

|-
|At the prompt type

“'''grep -i “computers” grepdemo.txt'''<nowiki>” [</nowiki>enter]

|The pattern matching is '''case sensitive'''.

To make it '''case''' insensitive, we need to use the '''minus i ''' option with '''grep'''.Come back to our terminal

Type:

'''grep space (minus) i space (within double quotes) “'''computers”''' after the '''double quotes space grepdemo.txt'''

Press ''' Enter.'''

|-
|
|This will now enlist all the four entries.

|-
|At the prompt type

“'''grep -iv “pass” grepdemo.txt'''<nowiki>” [</nowiki>enter]
|So we saw, '''grep''' enlists only those lines of files that match a given pattern.

|-
|
|We may do the reverse.

It is possible to make '''grep''' enlist only those lines that '''do not''' match the pattern.

|-
|
|For that we have the '''minus v''' option.

|-
|
|Say, we want to enlist those entries of students who have not passed.

|-
|At the prompt type

“'''grep -iv “pass” grepdemo.txt > notpass.txt'''<nowiki>” [</nowiki>enter]

|We can also store this result in another file

For this type:

'''grep space minus iv space''' within double quotes '''pass after the double quotes space grepdemo.txt space greater than sign space notpass.txt '''

Press '''Enter.'''

|-
|At the prompt type

'''“cat notpass.txt”'''
|To see the content of file, type:

'''cat space notpass.txt '''

Press '''Enter'''.

The output is displayed.

|-
|At the prompt type

“'''grep -i “fail” grepdemo.txt'''<nowiki>” [</nowiki>enter]
|Now at the '''prompt''' type:

'''grep space minus i space''' within double quotes '''fail''' after the double quotes space '''grepdemo.txt'''

and Press '''Enter.'''

|-
|
|This is different.

This will include those students who are failed but their result is incomplete.

|-
|At the prompt type

“'''grep -in “fail” grepdemo.txt'''<nowiki>” [</nowiki>enter]
|If we want to see the line number in the file at which the enlisted entries are, we have the '''minus n''' option

|-
|
|Let us clear the '''prompt'''. Now type

"'''grep space -in space within double quote "fail" after the double quotes space grepdemo.txt'''

Press '''Enter'''.

The line number is displayed.

|-
|At the prompt type

“'''grep -i “ankit saraf” grepdemo.txt'''<nowiki>” [</nowiki>enter]
|The patterns so far have been of single word.

We may have multiword patterns as well.

But the entire pattern must be within '''quotes'''.

|-
|
|So type:

'''grep space minus i space''' within double quotes '''ankit space saraf after the double quotes space grepdemo.txt '''

Press '''Enter'''.

We see that '''Ankit Saraf''''s record is displayed.

|-
|At the prompt type

“'''grep -i “fail” grepdemo.txt notpass.txt'''<nowiki>” [</nowiki>enter]
|We can also find patterns in multiple files.For this

Type:

'''grep space minus i space''' within double quotes '''fail after the double quotes space grepdemo.txt space notpass.txt'''

'''Press Enter'''.

The output is displayed.

|-
|
|With multiple files, '''grep''' will write the name of the file in which the entry was found.

'''grepdemo.txt''' '''notpass.txt'''

|-
|Highlight the relevant records.
|These are the records from '''notpass.txt''' file and these are the records from '''grepdemo.txt''' file.

|-
|At the prompt type

“'''grep -c “Fail” grepdemo.txt”''' <nowiki>[</nowiki>enter]
|Suppose we may only want to know the '''number of matches '''or '''count''' .

For that, we have the '''minus c''' option

So Type:

'''grep space minus c space''' within double quotes '''Fail''' with a capital F after the space grepdemo.txt'''

Press '''Enter'''.

This will give us the '''count''' of number of lines matched.

|-
|
|This brings us to the end of this tutorial.

Let us summarize.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Display Slide 6

Summary
| style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial we learnt,

*To see the content of a file
**eg. '''cat filename'''
*To list the entries of a particular stream
**eg. '''grep “computers” grepdemo.txt'''
*To ignore cases
**eg. '''grep -i “computers” grepdemo.txt'''
*Lines that do not match the pattern
**eg. '''grep -iv “pass” grepdemo.txt'''
*To list the line numbers with the entries
**eg.''' grep -in “fail” grepdemo.txt'''
*To store the result in another file
**eg. '''grep -iv “pass” grepdemo.txt > notpass.txt'''
*To know the count
**eg.''' grep -c “Fail” grepdemo.txt'''

|-
|Display Slide 7
|As an assignment,

Explore some other commands like '''-E, + and ?'''

|-
|Display Slide 8

Acknowledgement Slide
|Watch the video available at the link shown below.

It summarises the Spoken Tutorial project.

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

|-
|Display Slide 9

Spoken Tutorial Workshops
|The Spoken Tutorial Project Team

*Conducts workshops using spoken tutorials
*Gives certificates to those who pass an online test

For more details, please write to

'''contact@spoken-tutorial.org'''

|-
|Display Slide 10

Acknowledgement
|Spoken Tutorial Project is a part of the Talk to a Teacher project

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 Patil from IIT Bombay signning off. Thank you for joining.

|}

BOSS-Linux/C3/The-grep-command/English - Revision history

PoojaMoolya: Created page with "'''Title of script''': The grep command '''Author : Sachin Patil and Anirban''' '''Keywords:Search,Pattern,regular expressions,extended regular expression''' {|border=1 !..."