Linux/C3/More-on-grep-command/English - Revision history

Ashwini at 10:27, 14 December 2013

2013-12-14T10:27:07Z

Ashwini at 08:30, 14 December 2013

2013-12-14T08:30:07Z

Ashwini at 12:46, 13 December 2013

2013-12-13T12:46:51Z

Ashwini at 10:05, 1 July 2013

2013-07-01T10:05:30Z

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'…'

2013-07-01T09:39:15Z

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:0.106cm;"| '''Visual Cue'''
| style="border:1pt solid #000000;padding:0.106cm;"| '''Narration'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 1

| style="border:1pt solid #000000;padding:0.106cm;"| Welcome to this spoken tutorial on some more on '''grep''' command

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 2
| style="border:1pt solid #000000;padding:0.106cm;"| In this tutorial we will learn some more grep commands.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 3
| style="border:1pt solid #000000;padding:0.106cm;"| 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:0.106cm;"| Display Slide 4
| style="border:1pt solid #000000;padding:0.106cm;"| To practice this tutorial,

You should know Basics of linux terminal.

You should be aware of grep.

For relevant tutorials please visit our website:

http://spoken-tutorial.org

|-
| style="border:1pt solid #000000;padding:0.106cm;"| At the prompt type

“'''grep -e “electronics” -e “civil” grepdemo.txt”'''<nowiki> [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| We can match more than one patterns as well.

Then we have to use the '''-e''' option.

Say we want to find information for those who are either in '''civil''' or '''electronics'''.

We need to type:

'''grep''' space '''minus e''' space in double quotes '''electronics''' space '''minus e''' space in double quotes '''civil''' space '''grepdemo.txt'''

'''Press Enter.'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| At the prompt type

“'''grep -ie “choudhury” -ie “chowdhari” grepdemo.txt”'''<nowiki> [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| Say you need to look into people whose title is '''choudhury'''.

The problem is different people spell their titles in different way.

So what is the solution?.

In such cases we can use '''minus e''' option with '''minus i.'''

Type:

'''grep''' space '''minus''' '''ie''' space in double quotes '''choudhury''' space '''minus ie''' space in double quotes '''chowdhari''' space '''grepdemo.txt'''

'''Press Enter.'''

But there can be many other ways in which we can write the name.

How many '''-e''' options can we give.

Obviously there needs to be a better way and that way is through Regular expressions.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 5
| style="border:1pt solid #000000;padding:0.106cm;"| A regular expression provides a concise and flexible means for matching strings of text.

Such as particular characters, words or patterns of characters.

|-
| style="border:1pt solid #000000;padding:0.106cm;"|
| style="border:1pt solid #000000;padding:0.106cm;"| There are a number of regular expression characters.

Let us see them one by one.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 6
| style="border:1pt solid #000000;padding:0.106cm;"| The character class.

It allows us to specify a group of characters within a pair of square brackets .

Only one out of this group of characters is matched.

Eg<nowiki>. [</nowiki>abc] would mean that this regular expression matches either a or b or c.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| At the prompt

'''grep -i “ch<nowiki>[</nowiki>ao<nowiki>][</nowiki>uw]dh<nowiki>[</nowiki>ua]r<nowiki>[</nowiki>yi]”'''

'''grepdemo.txt'''<nowiki> [</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| Like to match '''choudhury''' we may use the command

type at the prompt

'''grep''' space '''minus i''' space in double quotes '''ch<nowiki>[</nowiki>ao<nowiki>][</nowiki>uw]dh<nowiki>[</nowiki>ua]r<nowiki>[</nowiki>yi]''' space '''grepdemo.txt'''

'''Press Enter.'''

It still does not match '''choudhuree'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 7
| style="border:1pt solid #000000;padding:0.106cm;"| If we want to specify a large range then write:

first letter dash last letter of the range

Like to match any digit we simply write<nowiki> [0-9].</nowiki>

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 8

| style="border:1pt solid #000000;padding:0.106cm;"| The '''<nowiki>*</nowiki>''' refers to 0 or more occurrences of the immediately preceding character.

For example '''ab<nowiki>*</nowiki>''' can match '''a,ab,abb,abbb''' etc.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| At the prompt

'''grep -i “m<nowiki>[</nowiki>ei]*raa<nowiki>*” </nowiki>grepdemo.txt'''

<nowiki>[</nowiki>enter]

| style="border:1pt solid #000000;padding:0.176cm;"| So to match the students name whose name is '''Mira'''

We write at the prompt:

'''grep''' space '''minus i''' space in double quotes '''m<nowiki>[</nowiki>ei] asterisk r a a''' '''asterisk''' space '''grepdemo.txt'''

'''Press Enter.'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 9
| style="border:1pt solid #000000;padding:0.106cm;"| The '''dot “.”'''

This regular expression matches any one character.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| At the prompt

'''grep “M...” grepdemo.txt'''

<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| Say we want to search any words that are 4 letters long and start with '''M.'''

We would simply write

'''grep''' space in double quotes '''M...''' space space '''grepdemo.txt'''

'''Press Enter.'''

Here the space within the quotes is important.

As it would match 5 or more letter words.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 10
| style="border:1pt solid #000000;padding:0.106cm;"| We may be specific about where in the line we want to search for our pattern.

It may be at the beginning of the line.

For that we have the '''caret sign.'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| At the prompt

'''grep “^A” grepdemo.txt'''

<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| Now if we want those entries whose roll numbers start with '''A.'''

We know that roll is the first field in the file.

We write at the prompt:

'''grep '''in double quotes '''caret A''' then space '''grepdemo.txt'''

'''Press Enter.'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 11

At the prompt, type:

'''grep<nowiki> “[78]...$ ” </nowiki>grepdemo.txt'''

<nowiki>[</nowiki>enter]
| style="border:1pt solid #000000;padding:0.106cm;"| Similarly to match a pattern at the end of the file, we have the '''dollar sign.'''

To find stipends between '''7000 '''to '''8999''' we have to write:

'''grep''' space in double quotes'''<nowiki> [78]</nowiki>'''...'''dolar sign''' space '''grepdemo.txt'''

'''Press Enter '''

This brings me to the end of this tutorial.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Display Slide 12

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

To match more than one pattern

eg. '''grep -e “electronics” -e “civil” grepdemo.txt'''

To check a word that has different spelling

eg. '''grep -ie “choudhury” -ie “chowdhari” grepdemo.txt'''

Character class

eg.''' grep -i “ch<nowiki>[</nowiki>ao<nowiki>][</nowiki>uw]dh<nowiki>[</nowiki>ua]r<nowiki>[</nowiki>yi]”'''

'''grepdemo.txt'''

The use of *

eg. '''grep -i “m<nowiki>[</nowiki>ei]*raa<nowiki>*” </nowiki>grepdemo.txt'''

To match any one character using dot

eg. '''grep “M...” grepdemo.txt'''

To match a pattern at the beginning of the file

eg. '''grep “^A” grepdemo.txt'''

To match a pattern at the end of the file

eg. '''grep<nowiki> “[78]...$ ” </nowiki>grepdemo.txt'''

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 13
| style="border:1pt solid #000000;padding:0.106cm;"| As an assignment,

List those entries that are 5 letters long and starts with Y.

|-
| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 14

Acknowledgement Slide
| style="border:1pt solid #000000;padding:0.106cm;"| 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:0.106cm;"| Display Slide 15

Spoken Tutorial Workshops
| style="border:1pt solid #000000;padding:0.106cm;"| 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:0.106cm;"| Display Slide 16

Acknowledgement
| style="border:1pt solid #000000;padding:0.106cm;"| 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:0.106cm;"| No Last Slide for tutorials created at IITB

Display the previous slide only and narrate this line.
| style="border:1pt solid #000000;padding:0.106cm;"|

|}

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

@@ Line 58: / Line 58: @@
 We need to type:
-'''grep''' space '''minus e''' space in double quotes '''electronics''' space '''minus e''' space in double quotes '''civil''' space '''grepdemo.txt'''
+'''grep''' space '''hyphen e''' space in double quotes '''electronics''' space '''hyphen e''' space in double quotes '''civil''' space '''grepdemo.txt'''
 '''Press Enter.'''
@@ Line 74: / Line 74: @@
-In such cases we can use '''minus e''' option with '''minus i.'''
+In such cases we can use '''hyphen e''' option with '''hyphen i.'''
@@ Line 80: / Line 80: @@
-'''grep''' space '''minus''' '''ie''' space in double quotes '''choudhury''' space '''minus ie''' space in double quotes '''chowdhari''' space '''grepdemo.txt'''
+'''grep''' space '''hyphen''' '''ie''' space in double quotes '''choudhury''' space '''hyphen ie''' space in double quotes '''chowdhari''' space '''grepdemo.txt'''
 '''Press Enter.'''
@@ Line 128: / Line 128: @@
-'''grep''' space '''minus i''' space in double quotes '''ch<nowiki>[</nowiki>ao<nowiki>][</nowiki>uw]dh<nowiki>[</nowiki>ua]r<nowiki>[</nowiki>yi]''' space '''grepdemo.txt'''
+'''grep''' space '''hyphen i''' space in double quotes '''ch<nowiki>[</nowiki>ao<nowiki>][</nowiki>uw]dh<nowiki>[</nowiki>ua]r<nowiki>[</nowiki>yi]''' space '''grepdemo.txt'''
@@ Line 172: / Line 172: @@
-'''grep''' space '''minus i''' space in double quotes '''m<nowiki>[</nowiki>ei] asterisk r a a''' '''asterisk''' space '''grepdemo.txt'''
+'''grep''' space '''hyphen i''' space in double quotes '''m<nowiki>[</nowiki>ei] asterisk r a a''' '''asterisk''' space '''grepdemo.txt'''

@@ Line 1: / Line 1: @@
-'''Title of script''': The grep command and Regular Expressions
+'''Title of script''': More on grep command
 '''Author : Sachin Patil'''
@@ Line 16: / Line 16: @@
-| style="border:1pt solid #000000;padding:0.106cm;"| Welcome to this spoken tutorial on some more on '''grep''' command
+| style="border:1pt solid #000000;padding:0.106cm;"| Welcome to the spoken tutorial on more on '''grep''' command
 |-
 | style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 2
 | style="border:1pt solid #000000;padding:0.106cm;"| In this tutorial we will learn some more grep commands.
 |-
@@ Line 28: / Line 30: @@
 '''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 34: / Line 36: @@
 |-
 | style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 4
-| style="border:1pt solid #000000;padding:0.106cm;"| To practice this tutorial,
+| style="border:1pt solid #000000;padding:0.106cm;"| As prerequisites
 You should know Basics of linux terminal.
@@ Line 52: / Line 54: @@
 Then we have to use the '''-e''' option.
 Say we want to find information for those who are either in '''civil''' or '''electronics'''.
@@ Line 61: / Line 64: @@
 '''Press Enter.'''
 |-
@@ Line 84: / Line 89: @@
 '''Press Enter.'''
 But there can be many other ways in which we can write the name.
@@ Line 123: / Line 129: @@
 '''grepdemo.txt'''<nowiki> [</nowiki>enter]
-| style="border:1pt solid #000000;padding:0.106cm;"| Like to match '''choudhury''' we may use the command
+| style="border:1pt solid #000000;padding:0.106cm;"| To match '''choudhury''' we may type at the prompt
-−
 type at the prompt
@@ Line 133: / Line 137: @@
 '''Press Enter.'''
-It still does not match '''choudhuree'''
+The output is displayed.
 |-
@@ Line 142: / Line 148: @@
-Like to match any digit we simply write<nowiki> [0-9].</nowiki>
+Suppose we like to match any digit we simply write<nowiki> [0-9].
 |-
@@ Line 176: / Line 184: @@
 '''Press Enter.'''
 |-
-| style="border:1pt solid #000000;padding:0.106cm;"| Display Slide 9
+| style="border:1pt solid #000000;padding:0.106cm;"|
 | style="border:1pt solid #000000;padding:0.106cm;"| The '''dot “.”'''
@@ Line 199: / Line 209: @@
 '''Press Enter.'''
@@ Line 205: / Line 217: @@
 As it would match 5 or more letter words.
@@ Line 258: / Line 268: @@
 '''Press Enter '''
 This brings me to the end of this tutorial.
 |-