add command lists (;, &&, ||) and $?

- split input at unquoted ;, && and || and run the commands like sh;
  variables are expanded per command when it runs
- $? and ${?} expand to the exit status of the last command,
  exit/quit without argument use it
- syntax errors for missing commands around operators (status 2)
- "command not found" message instead of the raw exec error, no more
  "exit status N" message when a command fails

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -8,8 +8,8 @@ Built-in commands:
   cd [dir]       - Change directory (cd with no args goes to home)
   pwd           - Print working directory
   echo [args]   - Echo arguments
-  exit [code]   - Exit shell with optional status code
-  quit [code]   - Quit shell with optional status code
+  exit [code]   - Exit shell with status code (default: $?)
+  quit [code]   - Quit shell with status code (default: $?)
   set VAR=val   - Set environment variable
   export VAR=val - Export environment variable
   help          - Show this help
@@ -29,6 +29,8 @@ Features:
     disabled with $NO_COLOR, TERM=dumb or when output is not a terminal
   - Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
     using an unset variable is an error, use ${VAR:-} for an empty default
+  - Command lists: a ; b (run both), a && b (b only if a succeeded),
+    a || b (b only if a failed); $? is the exit status of the last command
   - Non-interactive use: gosh -c 'command', gosh script, command | gosh;
     the exit status is the one of the last command
 
@@ -53,7 +55,31 @@ gosh -version
 
 Ohne Terminal bricht gosh bei einem fehlgeschlagenen Befehl nicht ab und beendet sich mit dem Exit-Status des letzten Befehls: `127`, wenn ein Befehl nicht gefunden wurde, `126`, wenn er nicht ausführbar ist, `128+n`, wenn er durch Signal `n` beendet wurde. Leere Zeilen und Zeilen, die mit `#` beginnen, werden übersprungen, Skripte können also mit `#!/usr/bin/gosh` beginnen.
 
-Damit funktionieren auch `ssh host befehl`, `scp` und `rsync`, wenn gosh als Login-Shell gesetzt ist. Da gosh `;`, `&&` und Pipes noch nicht kennt, darf der Befehl dabei aber nur aus einem einfachen Kommando bestehen.
+Damit funktionieren auch `ssh host befehl`, `scp` und `rsync`, wenn gosh als Login-Shell gesetzt ist. Befehle lassen sich mit `;`, `&&` und `||` verketten (z. B. `ssh host 'cd /srv && git pull'`), Pipes und Umleitungen kennt gosh aber noch nicht.
+
+### Befehlslisten und Exit-Status
+
+Mehrere Befehle in einer Zeile werden wie in `sh` verknüpft:
+
+| Liste      | Bedeutung                                         |
+|------------|---------------------------------------------------|
+| `a ; b`    | erst `a`, dann `b`                                |
+| `a && b`   | `b` nur, wenn `a` erfolgreich war (Exit-Status 0) |
+| `a \|\| b` | `b` nur, wenn `a` fehlgeschlagen ist              |
+
+`&&` und `||` werden von links nach rechts ausgewertet, `a && b || c` führt also `c` aus, wenn `a` oder `b` fehlschlägt. Variablen werden erst beim Ausführen des jeweiligen Befehls expandiert, `cd /tmp && echo $PWD` gibt also schon das neue Verzeichnis aus.
+
+`$?` (bzw. `${?}`) enthält den Exit-Status des letzten Befehls, `exit` ohne Argument beendet gosh mit diesem Status:
+
+```
+$ false; echo $?
+1
+$ gibtsnicht || echo "Status $?"
+gosh: gibtsnicht: command not found
+Status 127
+```
+
+Schlägt ein Programm fehl, gibt gosh selbst keine Meldung mehr aus (das Programm meldet den Fehler selbst), nur bei Fehlern von gosh, z. B. wenn ein Befehl nicht gefunden wird.
 
 ### Farben
 

main.go

@@ -12,6 +12,7 @@ import (
 	"os/user"
 	"path/filepath"
 	"runtime/debug"
+	"strconv"
 	"strings"
 	"syscall"
 	"unicode"
@@ -216,6 +217,9 @@ func expandVar(s string) (string, int, error) {
 			return "", 0, errors.New("missing } in variable reference")
 		}
 		name, def, hasDef := strings.Cut(s[2:end], ":-")
+		if name == "?" {
+			return strconv.Itoa(lastStatus), end + 1, nil
+		}
 		if !isVarName(name) {
 			return "", 0, fmt.Errorf("bad substitution: %s", s[:end+1])
 		}
@@ -229,6 +233,10 @@ func expandVar(s string) (string, int, error) {
 		return value, end + 1, nil
 	}
 
+	if len(s) > 1 && s[1] == '?' {
+		return strconv.Itoa(lastStatus), 2, nil
+	}
+
 	n := 1
 	for n < len(s) && isVarNameByte(s[n], n == 1) {
 		n++
@@ -693,13 +701,8 @@ func runScript(r io.Reader) int {
 	for {
 		line, err := readLine(r)
 		if trimmed := strings.TrimSpace(line); trimmed != "" && !strings.HasPrefix(trimmed, "#") {
-			cmdErr := execInput(line)
-			status = exitStatus(cmdErr)
-			// A command that ran and failed reports its own errors.
-			var exitErr *exec.ExitError
-			if cmdErr != nil && !errors.As(cmdErr, &exitErr) {
-				fmt.Fprintln(os.Stderr, "gosh:", cmdErr)
-			}
+			printError(execInput(line))
+			status = lastStatus
 		}
 		if err != nil {
 			if err != io.EOF {
@@ -747,7 +750,7 @@ func exitStatus(err error) int {
 		}
 		return exitErr.ExitCode()
 	}
-	if errors.Is(err, exec.ErrNotFound) || errors.Is(err, fs.ErrNotExist) {
+	if errors.Is(err, errCommandNotFound) || errors.Is(err, fs.ErrNotExist) {
 		return 127
 	}
 	if errors.Is(err, fs.ErrPermission) {
@@ -819,13 +822,142 @@ func interactive() {
 		}
 
 		// Execute the input
-		if err := execInput(line); err != nil {
-			fmt.Fprintln(os.Stderr, err)
-		}
+		printError(execInput(line))
 	}
 }
 
+// lastStatus is the exit status of the last command ($?).
+var lastStatus int
+
+// errCommandNotFound is returned when an external command does not exist.
+var errCommandNotFound = errors.New("command not found")
+
+// printError prints an error of a command to stderr. Commands that ran and
+// failed have already reported the problem themselves, only their exit
+// status is kept.
+func printError(err error) {
+	var exitErr *exec.ExitError
+	if err == nil || errors.As(err, &exitErr) {
+		return
+	}
+	fmt.Fprintln(os.Stderr, "gosh:", err)
+}
+
+// listItem is a command of a command list together with the operator that
+// connects it to the previous command ("" for the first one).
+type listItem struct {
+	op      string // "", ";", "&&" or "||"
+	command string
+}
+
+// splitList splits input at unquoted ;, && and ||. Quotes, escapes, ${...}
+// and comments are handled like in splitWords, but nothing is expanded yet:
+// that happens per command when it runs, so "cd /tmp && echo $PWD" works.
+func splitList(input string) ([]listItem, error) {
+	var (
+		items     []listItem
+		op        string
+		start     int
+		quote     byte
+		escaped   bool
+		wordStart = true // the next character starts a word
+	)
+
+	end := len(input)
+	add := func(i int, next string) error {
+		command := input[start:i]
+		if strings.TrimSpace(command) == "" {
+			// "a;" is fine, but an operator needs a command on both sides
+			if next != "" || op == "&&" || op == "||" {
+				if next == "" {
+					next = op
+				}
+				return fmt.Errorf("syntax error near unexpected token `%s'", next)
+			}
+			return nil
+		}
+		items = append(items, listItem{op: op, command: command})
+		return nil
+	}
+
+scan:
+	for i := 0; i < len(input); i++ {
+		ch := input[i]
+		isWordStart := wordStart
+		wordStart = false
+		switch {
+		case escaped:
+			escaped = false
+		case quote == '\'':
+			if ch == '\'' {
+				quote = 0
+			}
+		case ch == '\\':
+			escaped = true
+		case ch == '$' && i+1 < len(input) && input[i+1] == '{':
+			// Skip ${...} as a whole, like expandVar does
+			if j := strings.IndexByte(input[i:], '}'); j >= 0 {
+				i += j
+			}
+		case quote == '"':
+			if ch == '"' {
+				quote = 0
+			}
+		case ch == '"' || ch == '\'':
+			quote = ch
+		case ch == ' ' || ch == '\t' || ch == '\n':
+			wordStart = true
+		case ch == '#' && isWordStart:
+			end = i
+			break scan
+		case ch == ';',
+			ch == '&' && i+1 < len(input) && input[i+1] == '&',
+			ch == '|' && i+1 < len(input) && input[i+1] == '|':
+			next := input[i : i+1]
+			if ch != ';' {
+				next = input[i : i+2]
+			}
+			if err := add(i, next); err != nil {
+				return nil, err
+			}
+			i += len(next) - 1
+			op = next
+			start = i + 1
+			wordStart = true
+		}
+	}
+
+	// An unterminated quote or a trailing \ is reported by splitWords
+	if err := add(end, ""); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+// execInput executes a line of input: a list of commands separated by ;, &&
+// and ||. It returns the error of the last command that was run; errors of
+// earlier commands are printed. $? is updated after each command.
 func execInput(input string) error {
+	items, err := splitList(input)
+	if err != nil {
+		lastStatus = 2
+		return err
+	}
+
+	var lastErr error
+	for _, item := range items {
+		if (item.op == "&&" && lastStatus != 0) || (item.op == "||" && lastStatus == 0) {
+			continue
+		}
+		printError(lastErr)
+		lastErr = execCommand(item.command)
+		lastStatus = exitStatus(lastErr)
+	}
+	return lastErr
+}
+
+// execCommand executes a single simple command.
+func execCommand(input string) error {
 	// Split the input into the command and its arguments, expanding
 	// variables and ~ on the way.
 	args, err := splitWords(input)
@@ -879,7 +1011,7 @@ func execInput(input string) error {
 			fmt.Sscanf(args[1], "%d", &exitCode)
 			os.Exit(exitCode)
 		}
-		os.Exit(0)
+		os.Exit(lastStatus)
 	case "quit":
 		// quit with optional status code
 		if len(args) > 1 {
@@ -887,7 +1019,7 @@ func execInput(input string) error {
 			fmt.Sscanf(args[1], "%d", &exitCode)
 			os.Exit(exitCode)
 		}
-		os.Exit(0)
+		os.Exit(lastStatus)
 	case "set":
 		// set VAR=value - set environment variable
 		if len(args) < 2 {
@@ -919,8 +1051,8 @@ Built-in commands:
   cd [dir]       - Change directory (cd with no args goes to home)
   pwd           - Print working directory
   echo [args]   - Echo arguments
-  exit [code]   - Exit shell with optional status code
-  quit [code]   - Quit shell with optional status code
+  exit [code]   - Exit shell with status code (default: $?)
+  quit [code]   - Quit shell with status code (default: $?)
   set VAR=val   - Set environment variable
   export VAR=val - Export environment variable
   help          - Show this help
@@ -940,6 +1072,8 @@ Features:
     disabled with $NO_COLOR, TERM=dumb or when output is not a terminal
   - Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
     using an unset variable is an error, use ${VAR:-} for an empty default
+  - Command lists: a ; b (run both), a && b (b only if a succeeded),
+    a || b (b only if a failed); $? is the exit status of the last command
   - Non-interactive use: gosh -c 'command', gosh script, command | gosh;
     the exit status is the one of the last command`)
 		return nil
@@ -957,5 +1091,9 @@ Features:
 	cmd.Stderr = os.Stderr
 
 	// Execute the command return the error.
-	return cmd.Run()
+	err = cmd.Run()
+	if errors.Is(err, exec.ErrNotFound) {
+		return fmt.Errorf("%s: %w", sanitize(args[0]), errCommandNotFound)
+	}
+	return err
 }

main_test.go

@@ -1,8 +1,8 @@
 package main
 
 import (
-	"errors"
 	"bytes"
+	"errors"
 	"io"
 	"os"
 	"os/exec"
@@ -1348,3 +1348,126 @@ func TestReadLine_DoesNotReadAhead(t *testing.T) {
 		t.Errorf("readLine() consumed more than one line, %d bytes left", r.Len())
 	}
 }
+
+func TestSplitList(t *testing.T) {
+	tests := []struct {
+		input string
+		want  []listItem
+	}{
+		{"", nil},
+		{"   ", nil},
+		{"# only a comment", nil},
+		{"ls", []listItem{{"", "ls"}}},
+		{"a; b", []listItem{{"", "a"}, {";", " b"}}},
+		{"a;", []listItem{{"", "a"}}},
+		{"a && b || c", []listItem{{"", "a "}, {"&&", " b "}, {"||", " c"}}},
+		{`echo "a;b" 'c&&d' e\;f`, []listItem{{"", `echo "a;b" 'c&&d' e\;f`}}},
+		{`echo "x\"; y"`, []listItem{{"", `echo "x\"; y"`}}},
+		{"echo ${X:-a;b}; c", []listItem{{"", "echo ${X:-a;b}"}, {";", " c"}}},
+		{"echo a # b; c", []listItem{{"", "echo a "}}},
+		{"echo a#b; c", []listItem{{"", "echo a#b"}, {";", " c"}}},
+		{"echo a|b", []listItem{{"", "echo a|b"}}},
+	}
+	for _, tc := range tests {
+		got, err := splitList(tc.input)
+		if err != nil {
+			t.Errorf("splitList(%q) returned error: %v", tc.input, err)
+			continue
+		}
+		if !reflect.DeepEqual(got, tc.want) {
+			t.Errorf("splitList(%q) = %q, want %q", tc.input, got, tc.want)
+		}
+	}
+}
+
+func TestSplitList_SyntaxErrors(t *testing.T) {
+	for _, input := range []string{"; a", "a ;; b", "&& a", "a &&", "a ||", "a && ; b", "a || && b"} {
+		if _, err := splitList(input); err == nil || !strings.Contains(err.Error(), "syntax error") {
+			t.Errorf("splitList(%q) = %v, want syntax error", input, err)
+		}
+	}
+}
+
+func TestExecInput_Lists(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("D", dir)
+	tests := []struct {
+		input   string
+		created []string
+		missing []string
+		status  int
+	}{
+		{"touch $D/a; touch $D/b", []string{"a", "b"}, nil, 0},
+		{"false; touch $D/c", []string{"c"}, nil, 0},
+		{"true && touch $D/d", []string{"d"}, nil, 0},
+		{"false && touch $D/e", nil, []string{"e"}, 1},
+		{"false || touch $D/f", []string{"f"}, nil, 0},
+		{"true || touch $D/g", nil, []string{"g"}, 0},
+		{"false && touch $D/h || touch $D/i", []string{"i"}, []string{"h"}, 0},
+		{"true && false || touch $D/j", []string{"j"}, nil, 0},
+		{"gosh-no-such-command || touch $D/k", []string{"k"}, nil, 0},
+		{"true && sh -c 'exit 4'", nil, nil, 4},
+	}
+	for _, tc := range tests {
+		execInput(tc.input)
+		if lastStatus != tc.status {
+			t.Errorf("%q: $? = %d, want %d", tc.input, lastStatus, tc.status)
+		}
+		for _, name := range tc.created {
+			if _, err := os.Stat(filepath.Join(dir, name)); err != nil {
+				t.Errorf("%q: expected %s to be created", tc.input, name)
+			}
+		}
+		for _, name := range tc.missing {
+			if _, err := os.Stat(filepath.Join(dir, name)); err == nil {
+				t.Errorf("%q: %s must not be created", tc.input, name)
+			}
+		}
+	}
+}
+
+func TestExecInput_ExpandsPerCommand(t *testing.T) {
+	origDir, _ := os.Getwd()
+	defer os.Chdir(origDir)
+	dir := t.TempDir()
+	out := filepath.Join(dir, "out")
+	t.Setenv("GOSH_TEST_OUT", out)
+	os.Unsetenv("GOSH_TEST_LIST")
+	defer os.Unsetenv("GOSH_TEST_LIST")
+
+	// The variable is set by the first command and used by the second one
+	err := execInput(`set GOSH_TEST_LIST=hello && sh -c 'printf %s "$GOSH_TEST_LIST" > "$GOSH_TEST_OUT"'`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, _ := os.ReadFile(out); string(got) != "hello" {
+		t.Errorf("got %q, want %q", got, "hello")
+	}
+}
+
+func TestExpandVar_LastStatus(t *testing.T) {
+	execInput("sh -c 'exit 3'")
+	for _, input := range []string{"$?", "${?}"} {
+		words, err := splitWords("echo " + input)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if words[1] != "3" {
+			t.Errorf("%s = %q, want %q", input, words[1], "3")
+		}
+	}
+	execInput("true")
+	if words, _ := splitWords("echo $?"); words[1] != "0" {
+		t.Errorf("$? = %q after true, want 0", words[1])
+	}
+}
+
+func TestExecInput_CommandNotFound(t *testing.T) {
+	err := execInput("gosh-no-such-command")
+	if err == nil || err.Error() != "gosh-no-such-command: command not found" {
+		t.Errorf("got %v, want command not found", err)
+	}
+	if lastStatus != 127 {
+		t.Errorf("$? = %d, want 127", lastStatus)
+	}
+}