Day 7 of 90Days of Devops

Grep Commands Brief Introduction

• Grep stands for global regular expression print

• The basic use of the grep command is to find a particular keyword in a file and also it can be used to find multiple keywords from multiple locations

Grep command syntax

• grep [option] keyword filename

• Here the keyword is the word that you are searching for

• filename is the name of the file in which you are searching for the keyword

• There are multiple options like -c, -i, -v, -w, -n use case of each we have explained below

Use Cases for grep command

• case 1) To ignore the upper and lower case while searching for the keyword

$ grep -i keyword filename

• case 2)To search for everything except the keyword that we are passing

$ grep -v keyword filename

• case 3) To print how many times a given keyword is present in a file

$ grep -c keyword filename

• case 4) To search for the exact match of a given keyword in a file

$ grep -w keyword filename

• case 5 )To print the line number for the matched keyword in the file

$ grep -n keyword filename

#Here output will be the line numbers in which the keyword is present

• case 6) To search for the keyword in multiple files

$ grep keyword file1 file2 file3

#Here file1 ,file2 and file3 are the files in which we are searcching for
#keywords

• case 7) To search for multiple keywords in a file

$ grep -e keyword1 -e keyword2 filename 

#Here keyword1 is the first keyword that we are searching for 
#keyword2 is the second keyword that we are searching for in file 
#so in this way we can pass multiple keyword to search in a file

• case 8) To search for multiple keywords in multiple files

$ grep -e keyword1 -e keyword2 file1 file2 file3

#Here the above command will search for multiple keyword in multiple files
#like file1, file2, file3

• case 9)To search for keywords that we are passing in a file

$ grep -f kewords.txt file1 file2 file3

# Here we are passing a file named as keywords.txt this file contains all the 
# keywords that we want to search for 
#And this use case is helpful when we want to search for huge number of keyword
# file1 ,file2, file3 is the location where the keywords will be searched for

• case 10) Suppose we have 100 files in a directory (dirA) and we need to search for a keyword in all files

$ grep -R keyword dirA/

#Here -R means recursive so to check all files inside the directory recusively

• case 11) To print the matching lines which start with the given keyword

$ grep "^keyword" filename

example)
$ grep "^103" file1
#Here it will search for all the keywords that start with 103 in file1

• case 12) To print the matching lines which ends with the given keyword

$ grep "keyword$" filename

example)
$ grep "doctor$" file2
# Here it will serach for all the keywords that end with doctor in file2

⭐⭐😊😊Happy Learning to All !!⭐⭐😊😊

see you all in my next post !!!

Regards,

Amrit Manash