How Do I Use the Grep Command in Linux?

1. Basic usage.

The basic usage of the grep command is to find a line in a file that contains a specified pattern. For example, to find a line in a file that contains example, you can run the following command:

grep 'example'

grep will output all containments'example'of the line.

2. Ignore case.

By default, grep is case-sensitive. If you want to ignore case for searching, you can use the -i option. For example, to look for inclusions in a file'example', which is not case-sensitive, can execute the following command:

grep -i "example"

grep "^example"

This will output all the outputs that start with"example"The opening line.

Sometimes you need to find rows that don't contain a specified pattern. You can use the -v option to do a reverse search. For example, to find those that do not contain"example", you can execute the following commands:

grep -v "example"

grep will output all that are not included"example"of the line.

5. Count the number of matching rows.

If you only care about the number of matching rows, you can use the -c option to count the number of matched rows. For example, to count what is included in the file"example", you can execute the following command:

grep -c "example"

grep will output the number of matching rows.

If you want to recursively search for files in a directory and its subdirectories, you can use the -r option. For example, to find contains in the current directory and its subdirectories"example", you can execute the following commands:

grep -r "example".

You can use the head-1 command to fetch only the first row of grep data.

Use the command Beijing |head-n1 can only get the first row of data Beijing.

c,--bytes=[-k；k, which shows the first k bytes at the beginning of the document, -k, which does not show the last k bytes at the end of the document.

n,--lines=[-k:k, which indicates the first k lines of the document, and -k, which does not show the last k lines at the end of the document.

q,--quiet,--silent: The header of the file containing the given file name is not displayed.

Command Explained:The head command is similar to the tail command, the head command is used to view the beginning of the document with a specified number of character blocks, the first 10 lines of the document are displayed by default, if there is more than one file given, then add a file name title in front of each file that is being displayed.

grep command usage format:

head [Parameter] [File].