fixes #5

Makefile

@@ -3,4 +3,5 @@ all:
 	GOOS=windows GOARCH=amd64 go build -o binaries/cidr2ip-win64.exe cidr2ip.go
 	GOOS=linux GOARCH=386 go build  -o binaries/cidr2ip-linux32 cidr2ip.go
 	GOOS=linux GOARCH=amd64 go build -o binaries/cidr2ip-linux64 cidr2ip.go
+	GOOS=linux GOARCH=arm64 go build -o binaries/cidr2ip-linuxarm64 cidr2ip.go
 	GOOS=darwin GOARCH=amd64 go build -o binaries/cidr2ip-osx64 cidr2ip.go

README.md

@@ -7,32 +7,69 @@ This program converts IPv4 CIDR blocks into their constituent IP addresses.
 1. Commnd line arguments
 ```
 code@express:~$ cidr2ip 10.0.0.0/30 192.68.0.0/30
+10.0.0.0
 10.0.0.1
 10.0.0.2
+10.0.0.3
+192.68.0.0
 192.68.0.1
 192.68.0.2
-```
-
-The `-r` flag outputs IP ranges seperated by hyphen.
-
-```
-code@express:~$ cidr2ip -r 10.0.0.0/30 192.68.0.0/30
-10.0.0.1-10.0.0.2
-192.68.0.1-192.68.0.2
+192.68.0.3
 ```
 
 2. Piped input
 ```
 code@express:~$ cat cidrs.txt | cidr2ip
+127.0.0.1
+192.168.0.100
 192.168.0.101
 192.168.0.102
+192.168.0.103
+10.0.0.0
+10.0.0.1
+10.0.0.2
+10.0.0.3
+10.0.0.4
+10.0.0.5
+10.0.0.6
+10.0.0.7
 ```
 
 3. File input
 ```
-code@express:~$ cidr2ip -f cidrs.txt
+code@express:~$ cidr2ip -i cidrs.txt
+127.0.0.1
+192.168.0.100
 192.168.0.101
 192.168.0.102
+192.168.0.103
+10.0.0.0
+10.0.0.1
+10.0.0.2
+10.0.0.3
+10.0.0.4
+10.0.0.5
+10.0.0.6
+10.0.0.7
+```
+
+4. File output
+```
+code@express:~$ cidr2ip -i cidrs.txt -o results.txt
+code@express:~$ cat results.txt
+127.0.0.1
+192.168.0.100
+192.168.0.101
+192.168.0.102
+192.168.0.103
+10.0.0.0
+10.0.0.1
+10.0.0.2
+10.0.0.3
+10.0.0.4
+10.0.0.5
+10.0.0.6
+10.0.0.7
 ```
 
 ### Install

cidr2ip.go

@@ -5,21 +5,23 @@ import (
 	"flag"
 	"fmt"
 	"log"
-	"net"
 	"os"
 	"regexp"
+
+	"github.com/adedayo/cidr"
 )
 
 const (
-	Version = "2.0.0"
+	Version = "3.0.0"
 	IPRegex = `\b(?:\d{1,3}\.){3}\d{1,3}\b$`
 )
 
 var (
-	cidrFilePtr = flag.String("f", "",
-		"[Optional] Name of file with CIDR blocks")
-	printRangesPtrPtr = flag.Bool("r", false,
-		"[Optional] Print IP ranges instead of all IPs")
+	cidrFilePtr = flag.String("i", "",
+		"[Optional] Name of input file with CIDR blocks")
+	outputFilePtr = flag.String("o", "",
+		"[Optional] Name of output file for storing result")
+	outputWriterPtr *bufio.Writer
 )
 
 func main() {
@@ -32,6 +34,16 @@ func main() {
 	}
 	args := os.Args[1:]
 
+	if *outputFilePtr != "" {
+		f, err := os.Create(*outputFilePtr)
+		if err != nil {
+			log.Fatal(err)
+		} else {
+			defer f.Close()
+			outputWriterPtr = bufio.NewWriter(f)
+		}
+	}
+
 	if *cidrFilePtr != "" {
 		file, err := os.Open(*cidrFilePtr)
 		if err != nil {
@@ -53,76 +65,44 @@ func main() {
 		}
 	} else if len(args) > 0 { // look for CIDRs on cmd line
 		var cidrs []string
-		if *printRangesPtrPtr == true {
-			cidrs = args[1:]
-		} else {
-			cidrs = args
-		}
+		cidrs = args
 
-		for _, cidr := range cidrs {
-			displayIPs(cidr)
+		for _, cs := range cidrs {
+			displayIPs(cs)
 		}
 	} else { // no piped input, no file provide and no args, display usage
 		flag.Usage()
 	}
+
+	if outputWriterPtr != nil {
+		outputWriterPtr.Flush()
+	}
 }
 
-func isIPAddr(cidr string) bool {
-	match, _ := regexp.MatchString(IPRegex, cidr)
+func isIPAddr(cs string) bool {
+	match, _ := regexp.MatchString(IPRegex, cs)
 	return match
 }
 
-func displayIPs(cidr string) {
-	var ips []string
-
-	// if a IP address, display the IP address and return
-	if isIPAddr(cidr) {
-		fmt.Println(cidr)
-		return
-	}
+func displayIPs(cs string) {
+	ips := cidr.Expand(cs)
 
-	ipAddr, ipNet, err := net.ParseCIDR(cidr)
-	if err != nil {
-		log.Print(err)
-		return
-	}
-
-	for ip := ipAddr.Mask(ipNet.Mask); ipNet.Contains(ip); increment(ip) {
-		ips = append(ips, ip.String())
-	}
-
-	// CIDR too small eg. /31
-	if len(ips) <= 2 {
-		return
-	}
-
-	if *printRangesPtrPtr == true {
-		fmt.Printf("%s-%s\n", ips[1], ips[len(ips)-2])
-	} else {
-		for _, ip := range ips[1 : len(ips)-1] {
-			fmt.Println(ip)
-		}
-	}
-}
-
-// The next IP address of a given ip address
-// https://stackoverflow.com/a/33925954
-func increment(ip net.IP) {
-	for i := len(ip) - 1; i >= 0; i-- {
-		ip[i]++
-		if ip[i] != 0 {
-			break
+	for _, ip := range ips {
+		if *outputFilePtr != "" {
+			outputWriterPtr.WriteString(ip + "\n")
+		} else {
+			println(ip)
 		}
 	}
 }
 
 func usage() {
 	fmt.Fprintf(os.Stderr, "CIDR to IPs version %s\n", Version)
-	fmt.Fprintf(os.Stderr, "Usage:   $ cidr2ip [-r] [-f <filename>] <list of cidrs> \n")
-	fmt.Fprintf(os.Stderr, "Example: $ cidr2ip -f cidrs.txt\n")
-	fmt.Fprintf(os.Stderr, "         $ cidr2ip 10.0.0.0/24\n")
-	fmt.Fprintf(os.Stderr, "         $ cidr2ip -r 10.0.0.0/24\n")
-	fmt.Fprintf(os.Stderr, "         $ cidr2ip -r -f cidrs.txt\n")
+	fmt.Fprintf(os.Stderr, "Usage:   $ cidr2ip [-i <filename>] [-o <filename>] [<list of cidrs>] \n")
+	fmt.Fprintf(os.Stderr, "Example: $ cidr2ip 10.0.0.0/27\n")
+	fmt.Fprintf(os.Stderr, "         $ cidr2ip -i cidrs.txt\n")
+	fmt.Fprintf(os.Stderr, "         $ cidr2ip -o results.txt 10.0.0.0/27\n")
+	fmt.Fprintf(os.Stderr, "         $ cidr2ip -i cidrs.txt -o results.txt\n")
 	fmt.Fprintf(os.Stderr, "         $ cat cidrs.txt | cidr2ip \n")
 	fmt.Fprintf(os.Stderr, "--------------------------\nFlags:\n")
 	flag.PrintDefaults()

go.mod

@@ -0,0 +1,5 @@
+module cidr2ip
+
+go 1.23.2
+
+require github.com/adedayo/cidr v0.1.5

go.sum

@@ -0,0 +1,3 @@
+github.com/adedayo/cidr v0.1.5 h1:O6N8M2CPOT7LAy2upOHnQ4YIKHD+VXAQc8/OalCsmnU=
+github.com/adedayo/cidr v0.1.5/go.mod h1:By6g82fmUcv8/Z/6JcDs1D4wO4gc/Ookb842bVCV6Io=
+github.com/urfave/cli v1.20.0/go.mod h1:70zkFmudgCuE/ngEzBv17Jvp/497gISqfk5gWijbERA=