run cmds in shell, cd & exit builtins

.gitignore

@@ -21,3 +21,5 @@
 # Go workspace file
 go.work
 
+# Output of go tooling
+shell

go.mod

@@ -0,0 +1,3 @@
+module gitea.futureblog.eu/andre/shell
+
+go 1.21.1

main.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"unicode"
+)
+
+func main() {
+	// Load the configuration file, if any
+
+	// Run command loop
+	myshell_loop()
+
+	// Perform any shutdown/cleanup
+}
+
+func myshell_loop() {
+	for {
+		// Read command
+		fmt.Printf("myshell> ")
+		line := read_line()
+
+		// Parse command
+		args := split_line(line)
+
+		// Execute command
+		output, err := execute(args)
+		if err != nil {
+			fmt.Println("error during exec command:", err)
+		} else {
+			fmt.Printf(string(output))
+		}
+	}
+	// Loop back to read command
+}
+
+func read_line() string {
+	// Read the command line
+	reader := bufio.NewReader(os.Stdin)
+	input, err := reader.ReadString('\n')
+	if err != nil {
+		fmt.Println("Error reading command line: ", err)
+	}
+
+	// Remove the newline character
+	input = strings.TrimSuffix(input, "\r\n")
+	input = strings.TrimSuffix(input, "\n")
+
+	return input
+}
+
+// Split the line into arguments
+func split_line(line string) []string {
+	fieldSeparator := func(c rune) bool {
+		return unicode.IsSpace(c) || c == '\a'
+	}
+	args := strings.FieldsFunc(line, fieldSeparator)
+
+	return args
+}
+
+var builtin_cmds = map[string]func([]string) ([]byte, error){
+	"cd": myshell_cd,
+	"exit": myshell_exit,
+}
+
+// Execute the command
+func execute(args []string) ([]byte, error) {
+	// Check for builtin commands
+	if cmd, ok := builtin_cmds[args[0]]; ok {
+		return cmd(args)
+	}
+
+	cmd := exec.Command("sh", "-c", strings.Join(args, " "))
+	output, err := cmd.CombinedOutput()
+	return output, err
+}
+
+func myshell_cd(args []string) ([]byte, error) {
+	if len(args) < 2 {
+		return nil, fmt.Errorf("cd: missing argument")
+	}
+	err := os.Chdir(args[1])
+	return nil, err
+}
+
+func myshell_exit(args []string) ([]byte, error) {
+	os.Exit(0)
+	return nil, nil
+}

main_test.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestSplitLine(t *testing.T) {
+	tests := []struct {
+		line string
+		want []string
+	}{
+		{"", []string{}},
+		{"arg1 arg2 arg3", []string{"arg1", "arg2", "arg3"}},
+		{"   arg1\targ2\narg3\rarg4\aarg5  ", []string{"arg1", "arg2", "arg3", "arg4", "arg5"}},
+		{"\"quoted arg\" 'another arg'", []string{"\"quoted", "arg\"", "'another", "arg'"}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.line, func(t *testing.T) {
+			if got := split_line(tt.line); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("split_line(%q) = %v, want %v", tt.line, got, tt.want)
+			}
+		})
+	}
+}