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

Nancyvarkey at 18:09, 14 December 2013

2013-12-14T18:09:28Z

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Ashwini at 10:27, 14 December 2013

2013-12-14T10:27:53Z

Ashwini at 08:10, 14 December 2013

2013-12-14T08:10:11Z

Ashwini at 08:02, 14 December 2013

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Ashwini at 07:59, 14 December 2013

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Ashwini at 07:54, 14 December 2013

2013-12-14T07:54:27Z

Ashwini at 10:04, 1 July 2013

2013-07-01T10:04:25Z

Ashwini: Created page with ''''Title of script''': The grep command and Regular Expressions '''Author : Anirban Roy Choudhury''' '''Keywords:Search,Pattern,regular expressions,extended regular expression'…'

2013-07-01T09:21:22Z

Created page with ''''Title of script''': The grep command and Regular Expressions '''Author : Anirban Roy Choudhury''' '''Keywords:Search,Pattern,regular expressions,extended regular expression'…'

New page

'''Title of script''': The grep command and Regular Expressions

'''Author : Anirban Roy Choudhury'''

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

{| style="border-spacing:0;"
| style="border:1pt solid #000000;padding:0.097cm;"| <center>'''Visual Cue'''</center>
| style="border:1pt solid #000000;padding:0.097cm;"| <center>'''Narration'''</center>

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 1
| style="border:1pt solid #000000;padding:0.097cm;"| Welcome to the spoken tutorial on '''grep''' command

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 2
| style="border:1pt solid #000000;padding:0.097cm;"| In this tutorial we will learn usage of grep command.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 3
| style="border:1pt solid #000000;padding:0.097cm;"| To record this tutorial, I am using

'''Ubuntu Linux''' 12.04''' Operating System''' and

'''GNU BASH''' version 4.2.24(1)

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 4
| style="border:1pt solid #000000;padding:0.097cm;"| To practice this tutorial,

You should know Basics of linux terminal

For relevant tutorials please visit our website:

http://spoken-tutorial.org

|-
| style="border:1pt solid #000000;padding:0.097cm;"|
| style="border:1pt solid #000000;padding:0.097cm;"| 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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 5
| style="border:1pt solid #000000;padding:0.097cm;"| '''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.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Open

“'''grepdemo.txt'''<nowiki>” [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.097cm;"| We will demonstrate usage of '''grep''' using a demo file '''grepdemo.txt'''

Let us see the content of the file

This is a file that has 13 entries.

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

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

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

At the prompt, type:

'''cat grepdemo.txt'''

| style="border:1pt solid #000000;padding:0.097cm;"| Let us see how grep works.

Say we want to see who are the students in the '''computers''' stream.

I would type:

'''grep '''space (in double quotes) '''computers''' space '''grepdemo.txt'''

This would enlist those entries where stream is '''computers'''

Compare the result with the original file.

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

Why is this so?

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

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

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

| style="border:1pt solid #000000;padding:0.097cm;"| The pattern matching is case sensitive.

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

Type:

'''grep''' space (minus''') i''' space (in double quotes) “'''computers”''' space '''grepdemo.txt'''

Press''' Enter.'''

This will now enlist all the four entries.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

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

| style="border:1pt solid #000000;padding:0.097cm;"| 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.

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

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

| style="border:1pt solid #000000;padding:0.097cm;"| We can also store this result in another file

Type:

'''grep''' space '''minus iv''' space in double quotes '''pass''' space '''grepdemo.txt''' space greater than sign space '''notpass.txt '''

'''Press Enter.'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

'''“cat notpass.txt”'''

| style="border:1pt solid #000000;padding:0.097cm;"| To see the content of file type:

'''cat space notpass.txt '''

'''press Enter'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

“'''grep -i “fail” grepdemo.txt'''<nowiki>” [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.097cm;"| Now

At the prompt type:

'''grep''' space '''minus i''' space in double quotes '''fail''' space '''grepdemo.txt'''

'''Press Enter.'''

This is different.

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

“'''grep -in “fail” grepdemo.txt'''<nowiki>” [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.097cm;"| If we want to see the line number in the file at which the enlisted entries are,

We have the '''minus n''' option

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

“'''grep -i “ankit saraf” grepdemo.txt'''<nowiki>” [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.097cm;"| The patterns so far have been of single word.

We may have multiword patterns as well.

But the entire pattern must be within quotes.

Type:

'''grep''' space '''minus i''' space in double quotes '''ankit''' space '''saraf''' space '''grepdemo.txt '''

'''Press Enter'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

“'''grep -i “fail” grepdemo.txt notpass.txt'''<nowiki>” [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.097cm;"| We can also find patterns in multiple files

Type:

'''grep '''space '''minus i''' space in double quotes '''fail''' space '''grepdemo.txt''' space '''notpass.txt'''

'''Press Enter'''

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| At the prompt type

“'''grep -c “Fail” grepdemo.txt”''' <nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.097cm;"| Suppose we may only want to know the '''number of matches '''or '''count''' .

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

Type:

'''grep''' space '''minus c''' space in double quotes '''Fail''' space '''grepdemo.txt'''

'''Press Enter'''

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

|-
| 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'''

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 7
| style="border:1pt solid #000000;padding:0.097cm;"| As an assignment,

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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 8

Acknowledgement Slide
| style="border:1pt solid #000000;padding:0.097cm;"| 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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 9

Spoken Tutorial Workshops
| style="border:1pt solid #000000;padding:0.097cm;"| 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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 10

Acknowledgement
| style="border:1pt solid #000000;padding:0.097cm;"| 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

|-
| style="border:1pt solid #000000;padding:0.097cm;"| No Last Slide for tutorials created at IITB

Display the previous slide only and narrate this line.
| style="border:1pt solid #000000;padding:0.097cm;"|

|}

@@ Line 242: / Line 242: @@
 | style="border:1pt solid #000000;padding:0.097cm;"| The patterns so far have been of single word.
 We may have multiword patterns as well.
@@ Line 249: / Line 254: @@
-Type:
+So Type:

@@ Line 1: / Line 1: @@
-'''Title of script''': The grep command and Regular Expressions
+'''Title of script''': The grep command
-'''Author : Sachin Patil'''
+'''Author : Sachin Patil and Anirban'''
 '''Keywords:Search,Pattern,regular expressions,extended regular expression'''

@@ Line 267: / Line 267: @@
 '''Press Enter'''
 |-
@@ Line 283: / Line 285: @@
 '''Press Enter'''
 With multiple files '''grep''' will write the name of the file in which the entry was found.
 |-
@@ Line 299: / Line 307: @@
-'''grep''' space '''minus c''' space in double quotes '''Fail''' space '''grepdemo.txt'''
+'''grep''' space '''minus c''' space in double quotes '''Fail''' with a capital F space '''grepdemo.txt'''
@@ Line 306: / Line 314: @@
 This will give us the '''count''' of number of lines matched.
 |-

@@ Line 235: / Line 235: @@
 We have the '''minus n''' option
 |-
@@ Line 240: / Line 248: @@
 “'''grep -i “ankit saraf” grepdemo.txt'''<nowiki>” [</nowiki>enter]
-| style="border:1pt solid #000000;padding:0.097cm;"| The patterns so far have been of single word.
+| style="border:1pt solid #000000;padding:0.097cm;"|
 The patterns so far have been of single word.

@@ Line 14: / Line 14: @@
 | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 1
 | style="border:1pt solid #000000;padding:0.097cm;"| Welcome to the spoken tutorial on '''grep''' command
 |-
 | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 2
-| style="border:1pt solid #000000;padding:0.097cm;"| In this tutorial we will learn usage of grep command.
+| style="border:1pt solid #000000;padding:0.097cm;"| In this tutorial we will learn
 |-
@@ Line 25: / Line 28: @@
 '''Ubuntu Linux''' 12.04''' Operating System''' and
-'''GNU BASH''' version 4.2.24(1)
+'''GNU BASH''' version 4.2.24
 Please note,''' GNU bash''' version 4 or above is recommended to practice this tutorial.
@@ Line 31: / Line 34: @@
 |-
 | style="border:1pt solid #000000;padding:0.097cm;"| Display Slide 4
-| style="border:1pt solid #000000;padding:0.097cm;"| To practice this tutorial,
+| style="border:1pt solid #000000;padding:0.097cm;"| As prerequisites
 You should know Basics of linux terminal
@@ Line 52: / Line 55: @@
 To find a keyword in a paragraph or a line, we use grep command
 |-
@@ Line 67: / Line 71: @@
 “'''grepdemo.txt'''<nowiki>” [</nowiki>enter]
-| style="border:1pt solid #000000;padding:0.097cm;"| We will demonstrate usage of '''grep''' using a demo file '''grepdemo.txt'''
+| style="border:1pt solid #000000;padding:0.097cm;"| I will demonstrate usage of '''grep''' using a demo file '''grepdemo.txt'''
@@ Line 80: / Line 84: @@
 The fields are separated by a bar, which is called a '''delimiter'''.
 |-
@@ Line 97: / Line 102: @@
-Say we want to see who are the students in the '''computers''' stream.
+Say we want to use grep command to see who are the students in the '''computers''' stream.
-I would type:
+Now type on the terminal:
-'''grep '''space (in double quotes) '''computers''' space '''grepdemo.txt'''
+'''grep '''space (within double quotes) '''computers''' space '''grepdemo.txt'''
@@ Line 108: / Line 115: @@
-Compare the result with the original file.
+Now Compare the result with the original file.
-We see that the entry for''' Zubin''' is not enlisted.
+We see that the entry for ''' Zubin''' is not enlisted.
-Why is this so?
+Why this is so?
 This is because '''grep''' searched for the pattern '''“computers”''' with small '''c'''
@@ Line 129: / Line 137: @@
 | style="border:1pt solid #000000;padding:0.097cm;"| The pattern matching is case sensitive.
-To make it case insensitive, we need to use the '''minus i '''option with '''grep'''.
+To make it case insensitive, we need to use the '''minus i ''' option with '''grep'''.
 Type:
-'''grep''' space (minus''') i''' space (in double quotes) “'''computers”''' space '''grepdemo.txt'''
+'''grep''' space (minus''') i''' space (within double quotes) “'''computers”''' after the double quotes space '''grepdemo.txt'''
-Press''' Enter.'''
+Press ''' Enter.'''
 This will now enlist all the four entries.
 |-
@@ Line 172: / Line 181: @@
-Type:
+For this Type:
@@ Line 194: / Line 203: @@
 '''press Enter'''
 |-
@@ Line 204: / Line 214: @@
 At the prompt type:
-'''grep''' space '''minus i''' space in double quotes '''fail''' space '''grepdemo.txt'''
+'''grep''' space '''minus i''' space within double quotes '''fail''' after the double quotes space '''grepdemo.txt'''
@@ Line 224: / Line 234: @@
 We have the '''minus n''' option