From ec47b533e2d748f6831f0fd2f68e93d0954c1d8f Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Mon, 24 Aug 2026 22:49:01 -0700
Subject: Initial commit

---
 rsh.go | 182 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 182 insertions(+)
 create mode 100644 rsh.go

(limited to 'rsh.go')

diff --git a/rsh.go b/rsh.go
new file mode 100644
index 0000000..80c52e0
--- /dev/null
+++ b/rsh.go
@@ -0,0 +1,182 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+type lexer struct {
+	insertConcat bool
+}
+
+func (l *lexer) splitTokens(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	n := 0
+Whitespace:
+	for ; n < len(data); n++ {
+		switch data[n] {
+		case ' ', '\t':
+			l.insertConcat = false
+		case '#':
+			i := n + 1
+			for ; i < len(data) && data[i] != '\n'; i++ {
+			}
+			if i < len(data) {
+				return i + 1, []byte(";"), nil
+			}
+			if atEOF {
+				return i, nil, nil
+			}
+			return n, nil, nil
+		case '\\':
+			if n+1 < len(data) && data[n+1] == '\n' {
+				n++
+				l.insertConcat = false
+				continue
+			}
+			fallthrough
+		default:
+			break Whitespace
+		}
+	}
+	data = data[n:]
+	if len(data) == 0 {
+		return n, nil, nil
+	}
+	switch data[0] {
+	case '$':
+		if l.insertConcat {
+			l.insertConcat = false
+			return n, []byte{}, nil
+		}
+		i := 1
+		for ; i < len(data); i++ {
+			if b := data[i]; !(b == '_' || '0' <= b && b <= '9' || 'a' <= b && b <= 'z' || 'A' <= b && b <= 'Z') {
+				break
+			}
+		}
+		if i == len(data) && !atEOF {
+			return n, nil, nil
+		}
+		if i < len(data) && data[i] == '(' {
+			i++
+		} else {
+			l.insertConcat = true
+		}
+		if i == 1 {
+			return 0, nil, fmt.Errorf(`invalid token "$"`)
+		}
+		return n + i, data[:i], nil
+	case '<', '>':
+		if len(data) == 1 && !atEOF {
+			return n, nil, nil
+		}
+		l.insertConcat = false
+		if len(data) > 1 && data[1] == '(' {
+			return n + 2, data[:2], nil
+		}
+		return n + 1, data[:1], nil
+	case '\'':
+		if l.insertConcat {
+			l.insertConcat = false
+			return n, []byte{}, nil
+		}
+		i := 1
+		for ; i < len(data); i++ {
+			if data[i] == '\'' {
+				if i+1 == len(data) && !atEOF {
+					return n, nil, nil
+				}
+				if i+1 == len(data) || data[i+1] != '\'' {
+					break
+				}
+			}
+		}
+		if i == len(data) {
+			if atEOF {
+				return 0, nil, fmt.Errorf("unterminated string")
+			}
+			return n, nil, nil
+		}
+		i++
+		l.insertConcat = true
+		return n + i, data[:i], nil
+	case '\n':
+		l.insertConcat = false
+		return n + 1, []byte(";"), nil
+	case '&':
+		if len(data) == 1 && !atEOF {
+			return n, nil, nil
+		}
+		l.insertConcat = false
+		if len(data) > 1 && data[1] == '&' {
+			return n + 2, data[:2], nil
+		}
+		return n + 1, data[:1], nil
+	case '|':
+		if len(data) == 1 && !atEOF {
+			return n, nil, nil
+		}
+		l.insertConcat = false
+		if len(data) > 1 && data[1] == '|' {
+			return n + 2, data[:2], nil
+		}
+		return n + 1, data[:1], nil
+	case ';':
+		l.insertConcat = false
+		return n + 1, data[:1], nil
+	case ')':
+		l.insertConcat = true
+		return n + 1, data[:1], nil
+	case '*':
+		if l.insertConcat {
+			l.insertConcat = false
+			return n, []byte{}, nil
+		}
+		l.insertConcat = true
+		return n + 1, data[:1], nil
+	default:
+		if l.insertConcat {
+			l.insertConcat = false
+			return n, []byte{}, nil
+		}
+		i := 1
+	Word:
+		for ; i < len(data); i++ {
+			switch data[i] {
+			case '\\':
+				if i+1 == len(data) && !atEOF {
+					return n, nil, nil
+				}
+				if i+1 < len(data) && data[i+1] == '\n' {
+					break Word
+				}
+			case '&', '|', '*', ')', ';', '$', '<', '>', '\'', '#', ' ', '\t', '\n':
+				break Word
+			}
+		}
+		if i == len(data) && !atEOF {
+			return n, nil, nil
+		}
+		l.insertConcat = true
+		return n + i, data[:i], nil
+	}
+}
+
+func splitTokens() bufio.SplitFunc {
+	return new(lexer).splitTokens
+}
+
+func main() {
+	scanner := bufio.NewScanner(os.Stdin)
+	scanner.Split(splitTokens())
+	var tokens []string
+	for scanner.Scan() {
+		tokens = append(tokens, scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	fmt.Printf("%q\n", tokens)
+}
-- 
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