From 29419eec3c4d05a894e692a4f722e70fe99af404 Mon Sep 17 00:00:00 2001
From: jienfak <jienfak@protonmail.com>
Date: Sun, 29 Sep 2019 01:06:14 +0500
Subject: [PATCH] cat: First implementation.

---
 cat/main.go | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 cat/main.go

diff --git a/cat/main.go b/cat/main.go
new file mode 100644
index 0000000..d377c4d
--- /dev/null
+++ b/cat/main.go
@@ -0,0 +1,58 @@
+package main
+
+import(
+	"fmt"
+	"os"
+	"io"
+	"log"
+	"flag"
+)
+
+const(
+	bufSiz = 1024
+)
+
+func catFile(file *os.File) error {
+	buf := make([]byte, bufSiz)
+	for {
+		n, err := file.Read(buf)
+		if n>0 {
+			fmt.Printf("%s", buf[:n])
+		}
+		if err == io.EOF {
+			break
+		}else if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+func openAndCatFile(filePath string) error {
+	file, err := os.Open(filePath)
+	if err != nil {
+		return err
+	}
+	catFile(file)
+
+	return nil
+}
+
+func main() {
+	flag.Parse()
+	warn := log.New(os.Stderr, os.Args[0]+": ", 0)
+	status := 0
+	if flag.NArg()>0 { // Files.
+		for _, pathFile := range flag.Args() {
+			err := openAndCatFile(pathFile)
+			if err != nil {
+				warn.Println(err)
+			}
+		}
+	} else { // Stdin.
+		err := catFile(os.Stdin)
+		if err != nil {
+			warn.Println(err)
+		}
+	}
+	os.Exit(status)
+}