Hello, everyone In this Article we are going to learn how we can search a string in Linux in a very simple and easy step-by-step approach.
The grep command is use to search a particular string from the file.
The grep is the best utility to find any string from any file.
If we want to find any word or line inside any file then we can use the grep command.
Before Jumping on the command we should know the syntax of the grep command
grep [options..][arguments..] filename
Argument and File name cannot skip but we can skip the options
1 ) How to search a word from the file
To search a particular word in a file then we can execute the below command. Here we are searching root word from /etc/passwd file
$ grep root /etc/passwd
2) How to search a word with the line number from the file
To display the output of the grep command with the line number then we can use the ( -n )option in the grep command.
$ grep -n root /etc/passwd
3)How to search case sensitive word from the file
To ignore the case-sensitive word from the file then we can use( -i )option in the grep command.
Here the Root keyword is in a capital letter still this can be searched. This will ignore the case sensitivity to the keyword that we are searching
$ grep -in Root /etc/passwd
4) How to find the word that is appearing at the starting of a line
If we only need a line where the root keyword is coming in 1st position, not in the mid or ending of the file then we need to execute below command.
We can add( ^ ) symbol in grep command
$ grep -in '^root' /etc/passwd5) How to find the word that is appearing at the ending of a line
If we need a line where no login is coming in the last part of the line inside the file then we can add a ( $ ) dollar special symbol.
$ grep -in 'nologin$' /etc/passwd
6)How to View the Lines coming after searching the word
If the root is coming inline 1 & 10 but we need after 2 lines where the word is coming then this command will give after 2 lines where the root word is there. Then we can use the( -A )option.
$ grep -in -A2 root /etc/passwd
7) How to View the Lines coming before searching the word
If the root is coming inline 10 but we need before 2 lines where the word is coming then this command will give before 2 lines where root word is there. We can use ( -B ) option in the grep command.
$ grep -in -B 2 root /etc/passwd 
8) How to View the Lines coming after & before searching the word
If the root is coming in line 10 but we need after 2 lines where the word is coming and before 2 lines where the word is coming. We can use the ( -C ) option in the grep command.
$ grep -in -C2 root /etc/passwd 
9) How to find Multiple Keyword in a file
If we want to find multiple words then add | symbol and we have to use egrep command in this situation egrep is use for enhanced grep.
$ egrep -in ‘root|nologin’ /etc/passwd
We can also use grep command to filter log file
Suppose that we need November month logs then we can run the following command
# grep -in 'Nov' /var/log/messages
If we need a particular date log then we can execute this command
# grep -in 'Nov 10' /var/log/messages
How to run grep command in the directory
$ grep -Rin root /etc/ This command will search the root word in every file in /etc/ directory this will search we can use this when we do not know the exact filename
How to check version Of the grep command
If we want to check what is the version of the grep command then we can execute the below command.
# grep --version
How to View the Most useful Options in the grep command
If we want to know the most useful options with the grep command then we can execute the below command.
$ grep --help
Conclusion
If you want to learn Linux in the most simple language then please click on this link.
If you want to see the man page of grep command online then click on this link
This is the complete knowledge of how we can find the string using the grep command in the Linux kernel using the rm command if you have any doubts please feel free to comment below. Please don’t forget to join our email subscription to get the latest updates on DevOps Articles.
