Allow only printing the results to console and only printing CIDRs

.gitignore

@@ -0,0 +1 @@
+/.idea/

README.md

@@ -24,7 +24,9 @@ Usage:
   -t string
         Domain or IP address (Required)
   -p string
-        Print results to console
+        Only print results to console
+  -c
+        Only print CIDRs
 ```
 
 ### Example

asnip.go

@@ -1,6 +1,6 @@
 /*
 asnip: ASN target organization IP range attack surface mapping
-by github.com/harleo — MIT License
+by github.com/harleo — MIT Licence
 */
 
 package main
@@ -9,7 +9,7 @@ import (
 	"bufio"
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -29,18 +29,29 @@ func (s sliceVal) String() string {
 	return str
 }
 
-func writeLines(lines []string, path string) error {
+func writeLines(lines []string, path string) {
 	file, err := os.Create(path)
 	if err != nil {
 		log.Fatalf("[!] Couldn't create file: %s\n", err.Error())
 	}
-	defer file.Close()
+	defer func(file *os.File) {
+		err := file.Close()
+		if err != nil {
+			log.Fatalf("Failed to write file %s: %s", file.Name(), err)
+		}
+	}(file)
 
 	w := bufio.NewWriter(file)
 	for _, line := range lines {
-		fmt.Fprintln(w, line)
+		_, err := fmt.Fprintln(w, line)
+		if err != nil {
+			log.Fatalf("Failed to write '%s' to file %s: %s", line, file.Name(), err)
+		}
+	}
+	flushErr := w.Flush()
+	if flushErr != nil {
+		log.Fatalf("Couldn't write file %s: %s", file.Name(), flushErr)
 	}
-	return w.Flush()
 }
 
 func httpRequest(URI string) string {
@@ -49,12 +60,17 @@ func httpRequest(URI string) string {
 		log.Fatalf("[!] Error sending request: %s\n", errGet.Error())
 	}
 
-	responseText, errRead := ioutil.ReadAll(response.Body)
+	responseText, errRead := io.ReadAll(response.Body)
 	if errRead != nil {
 		log.Fatalf("[!] Error reading response: %s\n", errRead.Error())
 	}
 
-	defer response.Body.Close()
+	defer func(Body io.ReadCloser) {
+		err := Body.Close()
+		if err != nil {
+			os.Exit(1)
+		}
+	}(response.Body)
 	return string(responseText)
 }
 
@@ -77,7 +93,7 @@ func CIDRToIP(cidr string) []string {
 	if err != nil {
 		log.Fatalf("[!] Failed to convert CIDR to IP: %s\n", err.Error())
 	}
-	
+
 	var ips []string
 	for ip := ip.Mask(ipnet.Mask); ipnet.Contains(ip); incrementIP(ip) {
 		ips = append(ips, ip.String())
@@ -91,8 +107,8 @@ func CIDRToIP(cidr string) []string {
 	}
 }
 
-func getIP(ipdomain string) []net.IP {
-	ip, err := net.LookupIP(ipdomain)
+func getIP(ipDomain string) []net.IP {
+	ip, err := net.LookupIP(ipDomain)
 	if err != nil {
 		log.Fatalf("[!] Error looking up domain: %s\n", err.Error())
 	}
@@ -114,8 +130,9 @@ func checkAPIRateLimit(response string) {
 
 func main() {
 	var (
-		target	= flag.String("t", "", "Domain or IP address (Required)")
-		print	= flag.Bool("p", false, "Print results to console")
+		target    = flag.String("t", "", "Domain or IP address (Required)")
+		onlyPrint = flag.Bool("p", false, "Only print results to console")
+		onlyCidrs = flag.Bool("c", false, "Only download list of CIDRs")
 	)
 
 	flag.Parse()
@@ -135,33 +152,36 @@ func main() {
 	checkAPIRateLimit(apiASResponse)
 
 	var CIDRSv4 []string
-	for _, cidrv4 := range apiASResponseInfo[3:] {
-		if !IsIPv6CIDR(cidrv4) {
-			CIDRSv4 = append(CIDRSv4, cidrv4)
+	for _, cidrV4 := range apiASResponseInfo[3:] {
+		if !IsIPv6CIDR(cidrV4) {
+			CIDRSv4 = append(CIDRSv4, cidrV4)
 		}
 	}
 	sort.Strings(CIDRSv4)
 
-	if *print {
+	if *onlyPrint {
 		fmt.Print(sliceVal(CIDRSv4))
-	}
-	fmt.Printf("[:] Writing %d CIDRs to file...\n", len(CIDRSv4))
-	writeLines(CIDRSv4, "cidrs.txt")
-
-	var ips []string
-	fmt.Println("[:] Converting to IPs...")
-	for _, cidr := range CIDRSv4 {
-		ips = append(ips, CIDRToIP(cidr)...)
+	} else {
+		fmt.Printf("[:] Writing %d CIDRs to file...\n", len(CIDRSv4))
+		writeLines(CIDRSv4, "cidrs.txt")
 	}
 
-	if *print {
-		for _, ipsValue := range ips {
-			fmt.Println(ipsValue)
+	if *onlyCidrs {
+		var ips []string
+		fmt.Println("[:] Converting to IPs...")
+		for _, cidr := range CIDRSv4 {
+			ips = append(ips, CIDRToIP(cidr)...)
+		}
+
+		if *onlyPrint {
+			for _, ipsValue := range ips {
+				fmt.Println(ipsValue)
+			}
+		} else {
+			fmt.Printf("[:] Writing %d IPs to file...\n", len(ips))
+			writeLines(ips, "ips.txt")
 		}
 	}
 
-	fmt.Printf("[:] Writing %d IPs to file...\n", len(ips))
-	writeLines(ips, "ips.txt")
-
 	fmt.Println("[!] Done.")
 }