How to search within a file?

You can search within a file using the grep command. Here’s how to do it:

Basic Search:
```
grep "search_term" filename.txt
```
This command searches for the specified search_term in filename.txt and displays the matching lines.
Case-Insensitive Search:
```
grep -i "search_term" filename.txt
```
This command performs a case-insensitive search.
Search for Whole Words:
```
grep -w "search_term" filename.txt
```
This command searches for the whole word only.
Display Line Numbers:
```
grep -n "search_term" filename.txt
```
This command shows the line numbers of the matching lines.
Search Recursively in Directories:
```
grep -r "search_term" /path/to/directory
```
This command searches for the term in all files within the specified directory and its subdirectories.

You can combine these options as needed. For example:

grep -i -n "search_term" filename.txt

This command performs a case-insensitive search and displays line numbers.