Stdin and Stdout enhancements

- Added stdin source and stdout destination options

Author: ScriptTiger

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2022 ScriptTiger
+Copyright (c) 2023 ScriptTiger
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -19,6 +19,8 @@ Argument                  | Description
  `-to_blackhole <IPv4>`   | Black hole address in destination
  `-to_blackhole_v6 <IPv6>`| IPv6 Black hole address in destination
 
+`-` can be used in place of `<file>` to designate standard input as the source and/or standard output as the destination. If standard input is used, standard output will be used by default if no destination file is given.
+
 By default, dragging and dropping a hosts file over a hosts-bl executable will automatically pick out lines beginning with `0.0.0.0`, check for and remove any duplicates, and compress it to 9 domains per line in standard hosts file format with `0.0.0.0` as the black hole address.
 
 In addition to removing duplicates by default, formats which support wild cards will automatically have wild card entries added and all child subdomains will be pruned from the list.

hosts-bl.go

@@ -3,6 +3,7 @@ package main
 //Import dependency packages
 import (
 	"index/suffixarray"
+	"io"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -50,9 +51,6 @@ func reducible(format string) bool {
 
 func main() {
 
-	//If no arguments given, display help
-	if len(os.Args) == 1 {help(0)}
-
 	//Declare variables
 	var (
 		//Flag pointers
@@ -68,6 +66,7 @@ func main() {
 
 		//Common variables
 		err error
+		rawData	[]byte
 		index *suffixarray.Index
 		iData []string
 		oData []string
@@ -96,6 +95,10 @@ func main() {
 	*cmtsPtr = false
 	dPtr = cmtsPtr
 
+	//Check if any data available from standard input and use it as default source if there is
+	stdinStat, _ := os.Stdin.Stat()
+	if stdinStat.Mode() & os.ModeNamedPipe != 0 {*ifilePtr = "-"}
+
 	//Push arguments to flag pointers
 	for i := 1; i < len(os.Args); i++ {
 		if strings.HasPrefix(os.Args[i], "-") {
@@ -144,18 +147,23 @@ func main() {
 		} else {help(4)}
 	}
 
-	//Set default input and output files if none given
-	if *ifilePtr == "" {
-		if os.Args[1] == "" {help(5)
-		} else {*ifilePtr = os.Args[1]}
+	//Print help if no input available
+	if *ifilePtr == "" {help(0)}
+
+	//Set default output if none specified
+	if *ofilePtr == "" {
+		if *ifilePtr == "-" {*ofilePtr = "-"
+		} else {*ofilePtr = *fmtPtr+"-"+filepath.Base(*ifilePtr)}
 	}
-	if *ofilePtr == "" {*ofilePtr = *fmtPtr+"-"+filepath.Base(*ifilePtr)}
 
 	//Initialize format string for quick reference
 	format := strings.ToLower(*fmtPtr)
 
-	//Initialize data from file
-	rawData, err := os.ReadFile(*ifilePtr)
+	//Initialize data from either stdin or file
+	if *ifilePtr == "-" {
+		rawData, err = io.ReadAll(os.Stdin)
+		if err != nil {help(5)}
+	} else {rawData, err = os.ReadFile(*ifilePtr)}
 	if err != nil {help(6)}
 
 	//Convert data to string and initialize variable for cleaning
@@ -216,9 +224,10 @@ func main() {
 		oData = nil
 	}
 
-	//If requested format is FQDN, just dump to file and exit
+	//If requested format is FQDN, just dump to file or stdout and exit
 	if format == "fqdn" {
-		os.WriteFile(*ofilePtr, []byte(strings.Join(iData, eol)+eol), 0644)
+		if *ofilePtr == "-" {os.Stdout.WriteString(strings.Join(iData, eol)+eol)
+		} else {os.WriteFile(*ofilePtr, []byte(strings.Join(iData, eol)+eol), 0644)}
 		os.Exit(0)
 	}
 
@@ -244,9 +253,10 @@ func main() {
 		oData = nil
 	}
 
-	//If requested format is reduced FQDN, just dump to file and exit
+	//If requested format is reduced FQDN, just dump to file or stdout and exit
 	if format == "rfqdn" {
-		os.WriteFile(*ofilePtr, []byte(strings.Join(iData, eol)+eol), 0644)
+		if *ofilePtr == "-" {os.Stdout.WriteString(strings.Join(iData, eol)+eol)
+		} else {os.WriteFile(*ofilePtr, []byte(strings.Join(iData, eol)+eol), 0644)}
 		os.Exit(0)
 	}
 
@@ -346,7 +356,8 @@ func main() {
 	iData = oData
 	oData = nil
 
-	//Write formatted data to output file and exit
-	os.WriteFile(*ofilePtr, []byte(strings.Join(iData, eol)+eol), 0644)
+	//Write formatted data to output file or stdout and exit
+	if *ofilePtr == "-" {os.Stdout.WriteString(strings.Join(iData, eol)+eol)
+	} else {os.WriteFile(*ofilePtr, []byte(strings.Join(iData, eol)+eol), 0644)}
 	os.Exit(0)
 }