Interactive output is what Nmap prints to the stdout stream, which usually appears on the terminal window you executed Nmap from. In other circumstances, you might have redirected stdout to a file or another application such as Nessus or an Nmap GUI may be reading the results. If a larger application is interpreting the results rather than printing Nmap output directly to the user, then using the XML output discussed in the section called “XML Output (-oX)” would be more appropriate.

This format has but one goal: to present results that will be valuable to a human reading over them. No effort is made to make these easily machine parsable or to maintain a stable format between Nmap versions. Better formats exist for these things. The toughest challenge is deciding which information is valuable enough to print. Omitting data that a user wants is a shame, though flooding the user with pages of mostly irrelevant output can be even worse. The verbosity, debugging, and packet tracing flags are available to shift this balance based on individual users' preferences.

This output format needs no extensive description here, as most Nmap examples in this book already show it. To understand Nmap's interactive output for a certain feature, see the section of this book dedicated to that feature. Typical examples of interactive output are given in Example 13.3, “Interactive output without verbosity enabled” and Example 13.4, “Interactive output with verbosity enabled”.