Grep demo

The grep command is a powerful command-line utility used to search for specific patterns in text and then print the lines that match those patterns. The name grep is an acronym for "globally search for a regular expression and print it out".

Let's work through some exercises by Sundeep at github.com/learnbyexample

Sample.txt

Hello World

Hi there
How are you

Just do-it
Believe it

banana
papaya
mango

Much ado about nothing
He he he
Adios amigo

Code.txt


fruit = []
fruit[0] = 'apple'
def fruit():
    print('banana')

1. Display lines containing an .

grep 'an' sample.txt

banana
mango

2. Display lines containing do as a whole word.

grep -w 'do' sample.txt

Just do-it

3. Lines that meet these conditions:

he matched irrespective of case

eitherWorld or Hi matched case senstively

$ grep -i 'he' sample.txt | grep -e 'World' -e 'Hi'

Hello World
Hi there

4. Lines containing fruit[0] literally.

$ grep -F 'fruit[0]' code.txt

fruit[0] = 'apple'

5. Display only the first two matching lines containing t from the sample.txt input file.

$ grep -m2 't' sample.txt

Hi there
Just do-it

6. Display only the first three matching lines that do not containhe

$ grep -m3 -v 'he' sample.txt

Hello World

How are you

7. Lines that contain do along with line number prefix.

$ grep -n 'do' sample.txt

6:Just do-it
13:Much ado about nothing

8. Count the number of times the string he is present, irrespective of case.

$ grep -io 'he' sample.txt | wc -l

9. Count the number of empty lines

$ grep -cx '' sample.txt

10. For both input files - display matching lines based on the search terms (one per line) present in the terms.txt file. Results should be prefixed with the corresponding input filename.

terms.txt

are
not
go
fruit[0]

$ grep -Ff terms.txt sample.txt code.txt

sample.txt:How are you
sample.txt:mango
sample.txt:Much ado about nothing
sample.txt:Adios amigo
code.txt:fruit[0] = 'apple'

to be continued....

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