Improve ZGrab Docs/--help (#524)

* added example of using stdin for input to the README

* added a description of zgrab2 to --help with example usages

* added example usages for http

* remove ./zgrab2 in favor of zgrab2

---------

Co-authored-by: Zakir Durumeric <zakird@gmail.com>

Author: phillip-stephens

README.md

@@ -96,7 +96,12 @@ domain.com
 10.0.0.1, , , 5678
 , domain.com, tag
 192.168.0.0/24, , tag
+```
+
+And an example of calling zgrab2 with input:
 
+```shell
+echo "en.wikipedia.org" | ./zgrab2 http --max-redirects=1 --endpoint="/wiki/New_York_City"
 ```
 
 ## Multiple Module Usage

modules/http/scanner.go

@@ -133,7 +133,11 @@ func (module *Module) NewScanner() zgrab2.Scanner {
 
 // Description returns an overview of this module.
 func (module *Module) Description() string {
-	return "Send an HTTP request and read the response, optionally following redirects."
+	desc := []string{
+		"Send an HTTP request and read the response, optionally following redirects",
+		"Ex: echo \"en.wikipedia.org\" | ./zgrab2 http --max-redirects=1 --endpoint=\"/wiki/New_York_City\"",
+	}
+	return strings.Join(desc, "\n")
 }
 
 // Validate performs any needed validation on the arguments

utility.go

@@ -22,6 +22,23 @@ const defaultDNSPort = "53"
 
 func init() {
 	parser = flags.NewParser(&config, flags.Default)
+	desc := []string{
+		// Using a long single line so the terminal can handle wrapping, except for Input/Examples which should be on
+		// separate lines
+		"zgrab2 is fast, modular L7 application-layer scanner. It is commonly used with tools like ZMap which identify " +
+			"\"potential services\", or services we know are active on a given IP + port, and these are fed into ZGrab2 " +
+			"to confirm and provide details of the service. It has support for a number of protocols listed below as " +
+			"'Available commands' including SSH and HTTP. By default, zgrab2 will accept input from stdin and output " +
+			"results to stdout, with updates and logs to stderr. Please see 'zgrab2 <command> --help' for more details " +
+			"on a specific command.",
+		"Input is taken from stdin or --input-file, if specified. Input is CSV-formatted with 'IP, Domain, Tag, Port' " +
+			"or simply 'IP' or 'Domain'. See README.md for more details.",
+		"",
+		"Example usages:",
+		"echo '1.1.1.1' | zgrab2 tls          # Scan 1.1.1.1 with TLS",
+		"echo example.com | zgrab2 http     # Scan example.com with HTTP",
+	}
+	parser.LongDescription = strings.Join(desc, "\n")
 }
 
 // NewIniParser creates and returns a ini parser initialized