From 65f21f805739cf8963da080aca9033be4ca99bd4 Mon Sep 17 00:00:00 2001
From: jienfak <jienfak@protonmail.com>
Date: Thu, 27 Feb 2020 08:37:41 +0500
Subject: [PATCH] tac: Simplified version implemented. cat: Simplified "Run"
 function initialization.

---
 cat/cat.go |  8 +++----
 goblin.go  |  2 ++
 tac/tac.go | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+), 4 deletions(-)
 create mode 100644 tac/tac.go

diff --git a/cat/cat.go b/cat/cat.go
index 5564b33..78330e8 100644
--- a/cat/cat.go
+++ b/cat/cat.go
@@ -34,11 +34,11 @@ func fcat(f *os.File) error {
 }
 
 func Run(args []string) int {	
-	flagSet := flag.NewFlagSet(args[0], flag.ExitOnError)
-	flagSet.Parse(args[1:])
+	status := 0
 	arg0 := args[0]
 	args = args[1:]
-	status := 0
+	flagSet := flag.NewFlagSet(arg0, flag.ExitOnError)
+	flagSet.Parse(args)
 	if len(args)>0 {
 		for _, p := range args {
 			e := cat(p)
@@ -50,4 +50,4 @@ func Run(args []string) int {
 		fcat(os.Stdin)
 	}
 	return status
-}
\ No newline at end of file
+}
diff --git a/goblin.go b/goblin.go
index 71ee4fb..d539a57 100644
--- a/goblin.go
+++ b/goblin.go
@@ -10,6 +10,7 @@ import(
 	"github.com/jienfak/goblin/gtrue"
 	"github.com/jienfak/goblin/gfalse"
 	"github.com/jienfak/goblin/sort"
+	"github.com/jienfak/goblin/tac"
 )
 
 func main() {
@@ -26,6 +27,7 @@ func main() {
 		"true" : gtrue.Run,
 		"false" : gfalse.Run,
 		"sort" : sort.Run,
+		"tac" : tac.Run,
 	}
 
 	if binBase := path.Base(os.Args[0]) ; binBase != "goblin" {
diff --git a/tac/tac.go b/tac/tac.go
new file mode 100644
index 0000000..d6efda1
--- /dev/null
+++ b/tac/tac.go
@@ -0,0 +1,67 @@
+package tac 
+/* Concatenate files in "stdout" reversed. */
+import(
+	"os"
+	"io"
+	"flag"
+	"fmt"
+	"bufio"
+)
+
+func reverse(a []string) chan string {
+	ret := make(chan string)
+	go func() {
+		l := len(a)
+		for i, _ := range a {
+			ret <- a[l-1-i]
+		}
+		close(ret)
+	}()
+	return ret
+}
+
+func tac(p string) error {
+	f, e := os.Open(p)
+	if e != nil {
+		return e
+	}
+	defer f.Close()
+	ftac(f)
+	return nil
+}
+
+
+func ftac(f *os.File) error {
+	r := bufio.NewReader(os.Stdin)
+	var lines []string
+	for {
+		line, e := r.ReadString('\n')
+		if e == io.EOF {
+			break
+		}
+		lines  = append(lines, line)
+	}
+	for l := range reverse(lines) {
+		fmt.Print(l)
+	}
+	return nil
+}
+
+func Run(args []string) int {	
+	status := 0
+	arg0 := args[0]
+	args = args[1:]
+	flagSet := flag.NewFlagSet(arg0, flag.ExitOnError)
+	flagSet.Parse(args)
+	if len(args)>0 {
+		for _, p := range args {
+			e := tac(p)
+			if e != nil {
+				fmt.Fprintf(os.Stderr, "%s: %s.\n", arg0, e)
+			}
+		}
+	} else {
+		ftac(os.Stdin)
+	}
+	return status
+}