implemented tail and fixed errors in input parser when there is a spacebar but no argument and when there is a arg with len 1

command/command.go

@@ -12,6 +12,7 @@ import (
 	"bbash/command/mv"
 	"bbash/command/pwd"
 	"bbash/command/rm"
+	"bbash/command/tail"
 	"bbash/command/touch"
 	"bbash/environment"
 	"bbash/input_parser"
@@ -56,6 +57,8 @@ func Run_command(in input_parser.Input, env *environment.Env) {
 		mv.Mv(in, env)
 	case "help":
 		help.Help(in, env)
+	case "tail":
+		tail.Tail(in, env)
 	default:
 		if !run_by_path(in, env) {
 			fmt.Println(fmt.Sprintf("No such command! (%s)", in.Instruction))

command/man/man.go

@@ -21,7 +21,7 @@ func Man(in input_parser.Input, env *environment.Env) {
 	case "cat":
 		fmt.Print("Outputs the contents of the given file")
 	case "head":
-			fmt.Print("Outputs first lines of a given file. 10 if non provided. Argument <file> <number of lines>")
+		fmt.Print("Outputs first lines of a given file. 10 if none provided. Argument <file> <number of lines>")
 	case "touch":
 		fmt.Print("Creates the given file")
 	case "rm":
@@ -30,8 +30,9 @@ func Man(in input_parser.Input, env *environment.Env) {
 		fmt.Print("Copies the given file. Argument: <source> <destination>")
 	case "mv":
 		fmt.Print("Moves a given file. Argument: <source> <destination>")
-		default: fmt.Println(fmt.Sprintf("No such command! (%s)", in.Instruction))
+	case "tail":
+		fmt.Print("Outputs last lines of a given file. 10 if none or 0 is provided. Argument <file> <number of lines>")
+	default:
+		fmt.Println(fmt.Sprintf("No such command! (%s)", in.Instruction))
 	}
 }
-
-

command/tail/tail.go

@@ -0,0 +1,84 @@
+package tail
+
+import (
+	"bbash/environment"
+	"bbash/input_parser"
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func Tail(in input_parser.Input, env *environment.Env) {
+	args := in.Args
+	var file_path string
+	var lines int
+	if len(args) >= 1 {
+		file_path = strings.TrimSpace(args[0])
+	} else {
+		fmt.Print(fmt.Sprintf("No arguments provided"))
+		return
+	}
+	if len(args) == 2 {
+		lines1, err := strconv.Atoi(strings.TrimSpace(args[1]))
+		lines = lines1
+		if err != nil {
+			fmt.Print(fmt.Sprintf("Second argument must be a integer"))
+			return
+		}
+	}
+	file, err := os.Open(file_path)
+	if err != nil {
+		fmt.Println(fmt.Sprintf("Error opening file: %s", err.Error()))
+		return
+	}
+	defer file.Close()
+	size, err := CountLines(file)
+	file.Seek(0, io.SeekStart)
+	scanner := bufio.NewScanner(file)
+	if lines == 0 {
+		for i := 0; i < size; i++ {
+			if !scanner.Scan() {
+				return
+			}
+			if i >= (size - 10) {
+				fmt.Println(fmt.Sprintf(scanner.Text()))
+			}
+		}
+	} else {
+		for i := 0; i < size; i++ {
+			if !scanner.Scan() {
+				return
+			}
+			if i >= (size - lines) {
+				fmt.Println(fmt.Sprintf(scanner.Text()))
+			}
+		}
+	}
+}
+func CountLines(r io.Reader) (int, error) {
+	var count int
+	var read int
+	var err error
+	var target []byte = []byte("\n")
+
+	buffer := make([]byte, 32*1024)
+
+	for {
+		read, err = r.Read(buffer)
+		if err != nil {
+			break
+		}
+
+		count += bytes.Count(buffer[:read], target)
+	}
+
+	if err == io.EOF {
+		return count, nil
+	}
+
+	return count, err
+}

input_parser/input_parser.go

@@ -36,8 +36,14 @@ func parse(input string) Input {
 	var flags []string
 	var args []string
 	for _, arg := range split[1:] {
-		if len(arg) == 1 && arg[0] == '-' {
+		if len(arg) == 0 {
 			continue
+		} else if len(arg) == 1 {
+			if arg[0] == '-' {
+				continue
+			} else {
+				args = append(args, strings.TrimSpace(arg))
+			}
 		} else if arg[0:2] == "--" {
 			var result = strings.TrimSpace(arg)
 			flags = append(flags, string(result[2:]))