Beam: beamsh is a mini-shell which runs processes and communicates with them over beam

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

beam/examples/beamsh/beamsh.go

@@ -0,0 +1,91 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"text/scanner"
+	"strings"
+)
+
+func main() {
+	s := &scanner.Scanner{}
+	s.Init(os.Stdin)
+	s.Whitespace = 1<<'\t' | 1<<' '
+	//s.Mode = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments
+	s.Mode = scanner.ScanStrings | scanner.ScanRawStrings | scanner.ScanIdents
+	expr, err := parse(s, "")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+	fmt.Printf("%d commands:\n", len(expr))
+	for i, cmd := range expr {
+		fmt.Printf("%%%d: %s\n", i, cmd)
+	}
+}
+
+type Command struct {
+	Args []string
+	Children []*Command
+}
+
+func (cmd *Command) subString(depth int) string {
+	var prefix string
+	for i:=0; i<depth; i++ {
+		prefix += "  "
+	}
+	s := prefix + strings.Join(cmd.Args, ", ")
+	if len(cmd.Children) > 0 {
+		s += " {\n"
+		for _, subcmd := range cmd.Children {
+			s += subcmd.subString(depth + 1)
+		}
+		s += prefix + "}"
+	}
+	s += "\n"
+	return s
+}
+
+func (cmd *Command) String() string {
+	return cmd.subString(0)
+}
+
+func parseArgs(s *scanner.Scanner) ([]string, rune, error) {
+	var args []string
+	tok := s.Scan()
+	for tok != scanner.EOF {
+		text := s.TokenText()
+		//fmt.Printf("--> [%s]\n", text)
+		if text == "{" || text == "}" || text == "\n" || text == "\r" || text == ";" {
+			return args, tok, nil
+		}
+		args = append(args, text)
+		tok = s.Scan()
+	}
+	return args, tok, nil
+}
+
+func parse(s *scanner.Scanner, opener string) ([]*Command, error) {
+	var expr []*Command
+	for {
+		args, tok, err := parseArgs(s)
+		if err != nil {
+			return nil, err
+		}
+		cmd := &Command{Args: args}
+		if s.TokenText() == "{" {
+			children, err := parse(s, "{")
+			if err != nil {
+				return nil, err
+			}
+			cmd.Children = children
+		}
+		if len(cmd.Args) > 0 || len(cmd.Children) > 0 {
+			expr = append(expr, cmd)
+		}
+		if tok == scanner.EOF {
+			break
+		}
+	}
+	return expr, nil
+}