How does Nmap save scan results to a file?

Nmap saves scan results to a file using output options that specify the format and destination of the results. Here are the common methods to save scan results:

Basic Output: To save the results in a simple text format, you can use the -oN option followed by the filename.
```
nmap <target_ip> -oN output.txt
```
XML Output: For saving results in XML format, use the -oX option.
```
nmap <target_ip> -oX output.xml
```
Grepable Output: To save results in a format that is easy to parse with grep, use the -oG option.
```
nmap <target_ip> -oG output.gnmap
```
All Formats: You can also save results in all formats simultaneously using the -oA option, which creates files with the same base name in all three formats (normal, XML, and grepable).
```
nmap <target_ip> -oA output
```

Replace <target_ip> with the actual IP address you want to scan, and output.txt, output.xml, or output.gnmap with your desired filenames. This allows you to keep a record of your scans for future reference or analysis.