add man page gosh(1) and include it in the deb/rpm packages

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
add assignments name=value and unset
2026-10-04 13:59:09 +02:00 · 2026-10-04 00:17:38 +02:00 · 2026-10-04 00:16:29 +02:00 · 2026-10-04 00:05:28 +02:00 · 2026-10-03 23:52:09 +02:00
13 changed files with 2382 additions and 192 deletions
@@ -1,2 +1,3 @@
 gosh
 dist/
 packaging/man/gosh.1.gz
@@ -12,6 +12,8 @@ before:
  hooks:
    - go mod tidy
    - go test ./...
    # Man page with the release version, gzipped for /usr/share/man
    - sh -c 'sed "s/@VERSION@/{{ .Version }}/" packaging/man/gosh.1 | gzip -9n > packaging/man/gosh.1.gz'
 builds:
  - id: gosh
@@ -50,6 +52,10 @@ archives:
      - src: README.md
        info:
          mode: 0644
      - src: packaging/man/gosh.1.gz
        dst: man/gosh.1.gz
        info:
          mode: 0644
 nfpms:
  - id: gosh
@@ -75,6 +81,10 @@ nfpms:
        dst: /usr/share/doc/gosh/README.md
        file_info:
          mode: 0644
      - src: packaging/man/gosh.1.gz
        dst: /usr/share/man/man1/gosh.1.gz
        file_info:
          mode: 0644
    scripts:
      postinstall: packaging/scripts/postinstall.sh
      postremove: packaging/scripts/postremove.sh
@@ -1,8 +1,8 @@
-`gosh` eine einfache Shell, geschrieben in golang.
+`gosh` eine Shell, in golang geschrieben.
 ```
 gosh - Go Shell
-Version: 0.2.1 (branch: main, commit: 03e791c)
+Version: 0.13.0 (branch: main, commit: f79fb0b)
 Built-in commands:
  cd [dir]       - Change directory (cd with no args goes to home)
@@ -12,6 +12,7 @@ Built-in commands:
  quit [code]   - Quit shell with status code (default: $?)
  set VAR=val   - Set environment variable
  export VAR=val - Export environment variable
  unset VAR     - Remove a variable
  source file   - Run the commands of file in this shell (also: . file)
  jobs          - List background and stopped jobs
  fg [%n]       - Continue job n (default: current job) in the foreground
@@ -19,6 +20,9 @@ Built-in commands:
  wait [%n]     - Wait for job n or all background jobs
  alias [name[=value] ...] - Define or show aliases (alias ll='ls -l')
  unalias name  - Remove an alias (unalias -a: all aliases)
  :             - Do nothing (exit status 0)
  break [n]     - Leave the innermost (or n-th) for/while/until loop
  continue [n]  - Continue with the next iteration of a loop
  help          - Show this help
 Features:
@@ -41,10 +45,19 @@ Features:
    GOSH_COLORS='user=1;33:path=36' (keys user, root, path, error; values
    are ANSI SGR codes, empty = no color); disabled with $NO_COLOR,
    TERM=dumb or when output is not a terminal
  - Variables: name=value sets a variable (like set), name=value command
    sets it only for that command; the value is not split or expanded as
    a pattern
  - Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
    using an unset variable is an error, use ${VAR:-} for an empty default
  - Command substitution: $(command) is replaced by the output of command
    (run in a subshell); unquoted it is split into words, "$(command)"
    stays one word
  - Command lists: a ; b (run both), a && b (b only if a succeeded),
    a || b (b only if a failed); $? is the exit status of the last command
  - Control structures: if cmd; then ...; elif cmd; then ...; else ...; fi,
    for x in words; do ...; done, while cmd; do ...; done, until ...,
    ! cmd negates the status; they can span several lines (prompt "> ")
  - Pipes (a | b) and redirections: < file, > file, >> file, 2> file,
    2>> file, 2>&1, >&2, &> file (stdout and stderr), &>> file
  - Job control: command & runs in the background, Ctrl+Z stops the
@@ -122,6 +135,93 @@ export LANG=de_DE.UTF-8
 export PATH=$HOME/bin:$PATH
 ```
 ### Kontrollstrukturen
 gosh kennt `if`, `for`, `while` und `until` wie `sh`, auf einer Zeile oder über mehrere Zeilen:
 ```bash
 if [ -f ~/.goshrc ]; then
  echo "rc vorhanden"
 elif [ -d ~/.config ]; then
  echo "nur .config"
 else
  echo "nichts"
 fi
 for f in *.log; do
  gzip "$f"
 done
 for i in {1..5}; do echo "Durchlauf $i"; done
 n=3
 while [ $n -gt 0 ]; do
  echo $n
  n=$(expr $n - 1)
 done
 until ping -c1 -W1 server >/dev/null; do sleep 1; done
 ```
 | Konstrukt                                   | Bedeutung                                                         |
 |---------------------------------------------|-------------------------------------------------------------------|
 | `if befehl; then …; elif …; then …; else …; fi` | führt den Zweig aus, dessen Bedingung den Exit-Status 0 hat   |
 | `for x in wörter; do …; done`               | setzt `x` nacheinander auf jedes Wort                             |
 | `while befehl; do …; done`                  | wiederholt, solange `befehl` erfolgreich ist                      |
 | `until befehl; do …; done`                  | wiederholt, bis `befehl` erfolgreich ist                          |
 | `! befehl`                                  | kehrt den Exit-Status um                                          |
 | `break [n]`, `continue [n]`                 | verlässt die (n-te) Schleife bzw. springt zum nächsten Durchlauf  |
 | `:`                                         | tut nichts, Exit-Status 0 (z. B. `while :; do …; done`)           |
 - Bedingungen sind normale Befehle (auch Listen mit `&&`/`||`), meist `test` bzw. `[ … ]` (z. B. `[ -f datei ]`, `[ "$a" = b ]`, `[ $n -lt 3 ]`).
 - Die Wörter nach `for … in` werden wie Argumente expandiert: `*.go`, `{1..10}`, `$VAR`, `$(befehl)`. Ohne `in` läuft die Schleife nicht (Positionsparameter gibt es nicht).
 - Variablen, `$(...)` und Wildcards im Rumpf werden bei jedem Durchlauf neu ersetzt.
 - Ist ein Befehl noch nicht vollständig (z. B. nach `if …; then` oder `for …` + Enter, nach `&&`, `|` oder einem `\` am Zeilenende), zeigt gosh den Fortsetzungs-Prompt `> `; Ctrl+C verwirft die angefangene Eingabe. Skripte und Startdateien lesen entsprechend weiter.
 - Ctrl+C bricht die ganze Befehlszeile ab, also auch eine Schleife (`while true; do sleep 1; done`).
 - Der Exit-Status ist der des zuletzt ausgeführten Befehls; ein `if` ohne passenden Zweig und eine Schleife ohne Durchlauf haben den Status 0.
 - Nicht unterstützt: Kontrollstrukturen in Pipes (`for …; done | sort`), mit Umleitung (`done > datei`) oder im Hintergrund (`done &`), außerdem `case`, Funktionen und `read`. Arithmetik geht z. B. mit `n=$(expr $n + 1)`.
 ### Variablen
 ```bash
 name=wert                 # Variable setzen (wie set name=wert)
 a=1 b=2                   # mehrere auf einmal
 gruss="Hallo Welt"        # Leerzeichen im Wert brauchen Anführungszeichen
 heute=$(date +%F)         # Ausgabe eines Befehls
 PATH=~/bin:$PATH          # ~ wird auch nach = und : ersetzt
 LANG=C sort datei         # nur für diesen einen Befehl
 unset name                # Variable entfernen
 echo $name ${name:-standard}
 ```
 - Eine Zuweisung ist ein Wort `name=wert` am Anfang eines Befehls, bei dem `name` und `=` ohne Anführungszeichen stehen und `name` aus Buchstaben, Ziffern und `_` besteht (nicht mit einer Ziffer beginnend). `"x=1"`, `x\=1` und `echo x=1` sind keine Zuweisungen.
 - Steht danach kein Befehl, wird die Variable in der Shell gesetzt. Wie bei `set` und `export` sind in gosh alle Variablen auch für gestartete Programme sichtbar (es gibt keine reinen Shell-Variablen).
 - Steht ein Befehl danach (`LANG=C sort datei`), gilt die Zuweisung nur für diesen Befehl, die Shell behält den alten Wert.
 - Der Wert wird nicht in Wörter geteilt und nicht als Wildcard oder `{a,b}` expandiert: `x=$(ls)` speichert die ganze Ausgabe, `x=*.go` speichert `*.go`. Variablen, `$(...)` und `~` (am Anfang, nach `=` und nach `:`) werden ersetzt.
 - `$?` ist nach einer Zuweisung der Status des letzten `$(...)` darin, sonst 0.
 - Variablen in den Argumenten werden ersetzt, bevor die Zuweisung davor gilt: `x=1 echo $x` gibt nicht `1` aus, sondern meldet `x: unbound variable` (wenn `x` vorher nicht gesetzt war).
 - In einer Pipeline (`x=1 | cat`) ändert eine Zuweisung die Shell nicht.
 ### Befehlsersetzung
 `$(befehl)` wird durch die Ausgabe von `befehl` ersetzt:
 ```
 $ echo "Heute ist $(date +%A)"
 Heute ist Montag
 $ kill $(pgrep -f mein-server)
 $ cd $(git rev-parse --show-toplevel)
 $ vim $(grep -l TODO *.go)
 $ echo "Dateien: $(ls | wc -l)"
 ```
 - Der Befehl läuft in einer eigenen Subshell (einem neuen gosh-Prozess): `cd`, `set` oder `export` darin ändern die laufende Shell nicht. Er darf alles enthalten, was gosh kann (Pipes, `;`, `&&`, Umleitungen, verschachtelte `$(...)`), und liest von der gleichen Eingabe, Fehlermeldungen gehen auf stderr.
 - Abschließende Zeilenumbrüche der Ausgabe werden entfernt.
 - Ohne Anführungszeichen wird die Ausgabe an Leerzeichen, Tabs und Zeilenumbrüchen in mehrere Wörter geteilt, `"$(befehl)"` bleibt ein einziges Wort (mit den Zeilenumbrüchen darin).
 - Anders als in `sh` werden Wildcards in der Ausgabe nicht expandiert, und Zeichen wie `;` oder `|` darin sind normaler Text: Die Ausgabe ist immer nur Daten.
 - Besteht ein Befehl nur aus einer Ersetzung (`$(false)`), ist ihr Exit-Status `$?`, sonst zählt der Status des Befehls. Ctrl+C während der Ersetzung bricht die ganze Zeile ab.
 - In `'...'` oder mit `\$(` wird nichts ersetzt. Die alte Schreibweise mit Backticks (`` `befehl` ``) und Arithmetik `$((1+2))` gibt es nicht.
 ### Befehlslisten und Exit-Status
 Mehrere Befehle in einer Zeile werden wie in `sh` verknüpft:
@@ -198,7 +298,7 @@ $ ls -d */            # nur Verzeichnisse
 - Versteckte Dateien (mit `.` am Anfang) werden nur gefunden, wenn das Muster selbst mit `.` beginnt: `*` findet `.bashrc` nicht, `.*rc` schon.
 - Passt keine Datei, bleibt das Wort unverändert stehen (wie in `sh`), `ls *.xyz` meldet dann also `ls` den Fehler.
 - In Anführungszeichen oder mit `\` davor sind die Zeichen normale Zeichen: `echo "*"`, `echo '*.go'`, `echo \*`.
- Werte von Variablen werden nicht als Muster behandelt (anders als in `sh`): Nach `set P=*.go` gibt `echo $P` wörtlich `*.go` aus. So kann ein Variablenwert nie unbemerkt auf viele Dateien passen. `echo $DIR/*.go` funktioniert dagegen, weil das `*` direkt in der Zeile steht.
+- Werte von Variablen werden nicht als Muster behandelt (anders als in `sh`): Nach `P='*.go'` gibt `echo $P` wörtlich `*.go` aus. So kann ein Variablenwert nie unbemerkt auf viele Dateien passen. `echo $DIR/*.go` funktioniert dagegen, weil das `*` direkt in der Zeile steht.
 - Bei einer Umleitung muss das Muster genau eine Datei treffen (`> *.log`), sonst meldet gosh `ambiguous redirect`.
 ### Pipes und Umleitungen
@@ -407,4 +507,4 @@ git push origin v0.1.0
 goreleaser release --clean
 ```
-Das Paket installiert `/usr/bin/gosh` und trägt die Shell in `/etc/shells` ein, sodass sie mit `chsh -s /usr/bin/gosh` gesetzt werden kann.
+Das Paket installiert `/usr/bin/gosh` und die Man-Page `gosh(1)` (`man gosh`, Quelle: `packaging/man/gosh.1`, lokal ansehen mit `man ./packaging/man/gosh.1`) und trägt die Shell in `/etc/shells` ein, sodass sie mit `chsh -s /usr/bin/gosh` gesetzt werden kann.
@@ -75,7 +75,7 @@ func expandAliasesIn(line string, active map[string]bool) string {
 	for i := 0; i < len(line); i++ {
 		ch := line[i]
 		if quote == 0 && !escaped && commandPos {
-			if ch == ' ' || ch == '\t' {
+			if ch == ' ' || ch == '\t' || ch == '\n' {
 				out.WriteByte(ch)
 				continue
 			}
@@ -96,6 +96,16 @@ func expandAliasesIn(line string, active map[string]bool) string {
 			}
 		}
 		if quote != '\'' && !escaped && isSubstStart(line, i) {
 			// $(...) is copied as it is; the subshell does not expand
 			// aliases
 			if end := substEnd(line, i); end >= 0 {
 				out.WriteString(line[i : end+1])
 				i = end
 				continue
 			}
 		}
 		out.WriteByte(ch)
 		switch {
 		case escaped:
@@ -0,0 +1,109 @@
 package main
 import (
 	"os"
 	"testing"
 )
 func TestTokenize_Assignments(t *testing.T) {
 	t.Setenv("HOME", "/home/u")
 	tests := []struct {
 		input  string
 		word   string
 		assign bool
 	}{
 		{"x=1", "x=1", true},
 		{"_a1=", "_a1=", true},
 		{`x="a b"`, "x=a b", true},
 		{"x=a=b", "x=a=b", true},
 		{"P=~/bin:~/go/bin", "P=/home/u/bin:/home/u/go/bin", true},
 		{"x=a~b", "x=a~b", true},
 		{"x=~", "x=/home/u", true},
 		// Not an assignment: quoted or escaped name or =, invalid name
 		{`"x=1"`, "x=1", false},
 		{`x"=1"`, "x=1", false},
 		{`x\=1`, "x=1", false},
 		{"1x=2", "1x=2", false},
 		{"=x", "=x", false},
 		{"a-b=1", "a-b=1", false},
 	}
 	for _, tc := range tests {
 		tokens, err := tokenize(tc.input)
 		if err != nil || len(tokens) != 1 {
 			t.Errorf("tokenize(%q) = %+v, %v", tc.input, tokens, err)
 			continue
 		}
 		if tokens[0].word != tc.word || tokens[0].assign != tc.assign {
 			t.Errorf("tokenize(%q) = %q (assign %v), want %q (assign %v)",
 				tc.input, tokens[0].word, tokens[0].assign, tc.word, tc.assign)
 		}
 	}
 	// The output of $(...) is not split in an assignment
 	tokens, _ := tokenize("x=$(echo a b) y")
 	if len(tokens) != 2 || tokens[0].word != "x=a b" || !tokens[0].assign {
 		t.Errorf("x=$(echo a b): %+v", tokens)
 	}
 }
 func TestExec_Assignments(t *testing.T) {
 	for _, name := range []string{"GOSH_A", "GOSH_B", "GOSH_C"} {
 		os.Unsetenv(name)
 		defer os.Unsetenv(name)
 	}
 	tests := []struct {
 		input string
 		want  string
 	}{
 		{"GOSH_A=1; echo $GOSH_A > out", "1\n"},
 		{"GOSH_A=1 GOSH_B=2; echo $GOSH_A$GOSH_B > out", "12\n"},
 		{`GOSH_A="a  b"; echo "$GOSH_A" > out`, "a  b\n"},
 		{"GOSH_A=$(printf 'a b\\nc'); echo \"$GOSH_A\" > out", "a b\nc\n"},
 		// No wildcard or brace expansion in the value
 		{"touch x.go; GOSH_A=*.go; echo \"$GOSH_A\" > out", "*.go\n"},
 		{"GOSH_A={a,b}; echo $GOSH_A > out", "{a,b}\n"},
 		// ... but as an argument, assignment-like words are normal words
 		{"echo GOSH_A={a,b} > out", "GOSH_A=a GOSH_A=b\n"},
 		// Before a command, only in its environment
 		{"GOSH_C=temp sh -c 'echo $GOSH_C' > out; echo ${GOSH_C:-unset} >> out", "temp\nunset\n"},
 		{"GOSH_A=old; GOSH_A=new sh -c 'echo $GOSH_A' > out; echo $GOSH_A >> out", "new\nold\n"},
 		// ... and before a builtin only while it runs
 		{"GOSH_C=temp pwd > /dev/null; echo ${GOSH_C:-unset} > out", "unset\n"},
 		// In a pipeline or with a command they do not change the shell
 		{"GOSH_C=x | cat; echo ${GOSH_C:-unset} > out", "unset\n"},
 		// Redirections are applied
 		{"GOSH_A=r > out", ""},
 		// In loops
 		{"for i in 1 2 3; do GOSH_A=$i; done; echo $GOSH_A > out", "3\n"},
 		{"GOSH_B=0; while [ $GOSH_B -lt 3 ]; do echo $GOSH_B >> out; GOSH_B=$(expr $GOSH_B + 1); done", "0\n1\n2\n"},
 		// Not assignments
 		{`echo "GOSH_A=1" GOSH_B=2 > out`, "GOSH_A=1 GOSH_B=2\n"},
 		// unset
 		{"GOSH_A=1; unset GOSH_A; echo ${GOSH_A:-gone} > out", "gone\n"},
 	}
 	for _, tc := range tests {
 		if got := runIn(t, tc.input); got != tc.want {
 			t.Errorf("%q: out = %q, want %q", tc.input, got, tc.want)
 		}
 	}
 	// The status of an assignment is the one of its last $(...)
 	for input, want := range map[string]int{
 		"GOSH_A=1":                       0,
 		"GOSH_A=$(false)":                1,
 		"GOSH_A=$(sh -c 'exit 3')":       3,
 		"GOSH_A=$(false) GOSH_B=$(true)": 0,
 	} {
 		runIn(t, input)
 		if lastStatus != want {
 			t.Errorf("%q: $? = %d, want %d", input, lastStatus, want)
 		}
 	}
 	if err := execInput("unset 1x"); err == nil || err.Error() != "unset: `1x': not a valid identifier" {
 		t.Errorf("unset 1x: %v", err)
 	}
 	if err := execInput(`"GOSH_A=1"`); err == nil || exitStatus(err) != 127 {
 		t.Errorf(`"GOSH_A=1" must be a command: %v`, err)
 	}
 }
@@ -15,12 +15,14 @@ import (
 const maxBraceWords = 100000
 // expandBraceWords applies brace expansion to every word of a command (the
-// text of a pipeline). Quoted or escaped braces and ${...} are left alone.
+// text of a pipeline). Quoted or escaped braces, ${...} and $(...) are left
 // alone.
 // A redirection target must expand to a single word.
 func expandBraceWords(input string) (string, error) {
 	var (
 		out           strings.Builder
 		afterRedirect bool // the next word is the target of a redirection
 		commandStart  = true
 	)
 	for i := 0; i < len(input); {
@@ -32,6 +34,8 @@ func expandBraceWords(input string) (string, error) {
 		case strings.IndexByte(";&|<>", ch) >= 0:
 			if ch == '<' || ch == '>' {
 				afterRedirect = true
 			} else {
 				commandStart = true
 			}
 			out.WriteByte(ch)
 			i++
@@ -41,6 +45,16 @@ func expandBraceWords(input string) (string, error) {
 			return out.String(), nil
 		default:
 			end := wordEnd(input, i)
 			if commandStart && !afterRedirect && isAssignment(input[i:end]) {
 				// name=value before the command: no brace expansion, like
 				// in bash
 				out.WriteString(input[i:end])
 				i = end
 				continue
 			}
 			if !afterRedirect {
 				commandStart = false
 			}
 			words, err := expandBraces(input[i:end])
 			if err != nil {
 				return "", err
@@ -56,6 +70,12 @@ func expandBraceWords(input string) (string, error) {
 	return out.String(), nil
 }
 // isAssignment reports whether a word starts with name= (unquoted).
 func isAssignment(word string) bool {
 	name, _, ok := strings.Cut(word, "=")
 	return ok && isVarName(name)
 }
 // wordEnd returns the end of the word starting at i: the next unquoted blank
 // or operator character.
 func wordEnd(s string, i int) int {
@@ -69,6 +89,10 @@ func wordEnd(s string, i int) int {
 			}
 		case ch == '\\':
 			i++
 		case isSubstStart(s, i):
 			if j := substEnd(s, i); j >= 0 {
 				i = j
 			}
 		case ch == '$' && i+1 < len(s) && s[i+1] == '{':
 			if j := strings.IndexByte(s[i:], '}'); j >= 0 {
 				i += j
@@ -103,6 +127,12 @@ func braceScan(s string, fn func(i, depth int) bool) {
 		case ch == '\\':
 			i++
 			continue
 		case isSubstStart(s, i):
 			// The subshell does its own brace expansion
 			if j := substEnd(s, i); j >= 0 {
 				i = j
 			}
 			continue
 		case ch == '$' && i+1 < len(s) && s[i+1] == '{':
 			if j := strings.IndexByte(s[i:], '}'); j >= 0 {
 				i += j
@@ -121,6 +121,7 @@ type token struct {
 	word    string // the word, if op == ""
 	pattern string // the word as glob pattern (quoted characters escaped)
 	glob    bool   // the word contains unquoted * ? or [ and is expanded
 	assign  bool   // the word is an assignment name=value (unquoted name and =)
 	fd      int    // the redirected file descriptor (for redirections)
 	dup     int    // the target file descriptor of >& and <&
 }
@@ -131,10 +132,13 @@ type token struct {
 //   - '...' is taken literally, nothing is expanded inside
 //   - "..." expands $VAR and ${VAR}; \ only escapes $ " \ and `
 //   - outside quotes \ escapes any character
 //   - $(command) is replaced by the output of command (see commandSubst);
 //     unquoted, the output is split into words at blanks and newlines
 //   - $VAR, ${VAR} and ${VAR:-default} are expanded outside single quotes;
 //     an unset variable is an error, so that e.g. "rm -rf $DIR/x" never runs
 //     with an empty $DIR
-//   - ~ and ~/... are expanded at the start of an unquoted word
+//   - ~ and ~/... are expanded at the start of an unquoted word, and after
 //     the = and : of an assignment (PATH=~/bin:~/go/bin)
 //   - unquoted |, <, >, >>, N<, N>, N>>, N>&M, N<&M, &> and &>> are operators
 //
 // Expanded values are never split into several words.
@@ -145,6 +149,9 @@ func tokenize(input string) ([]token, error) {
 		pat      strings.Builder // the word as glob pattern, quoted parts escaped
 		glob     bool            // the word contains unquoted * ? or [
 		inWord   bool            // a word has been started (even if it is still empty)
 		plain    = true          // the word so far has no quotes, escapes or expansions
 		assign   bool            // the word is an assignment name=value
 		tildeOK  bool            // ~ may be expanded here (after = or : of an assignment)
 		quote    byte
 		escaped  bool
 		rawStart = -1 // start of the current word in input
@@ -152,16 +159,17 @@ func tokenize(input string) ([]token, error) {
 	endWord := func() {
 		if inWord {
-			tokens = append(tokens, token{word: b.String(), pattern: pat.String(), glob: glob})
+			tokens = append(tokens, token{word: b.String(), pattern: pat.String(), glob: glob, assign: assign})
 		}
 		b.Reset()
 		pat.Reset()
-		glob = false
+		glob, assign, plain = false, false, true
 		inWord = false
 		rawStart = -1
 	}
 	// literal adds quoted, escaped or expanded text: it is never a pattern
 	literal := func(s string) {
 		plain = false
 		b.WriteString(s)
 		pat.WriteString(escapeGlob(s))
 	}
@@ -173,6 +181,8 @@ func tokenize(input string) ([]token, error) {
 	for i := 0; i < len(input); i++ {
 		ch := input[i]
 		afterAssignSep := tildeOK
 		tildeOK = false
 		switch {
 		case escaped:
 			if quote == '"' && !strings.ContainsRune("$\"\\`", rune(ch)) {
@@ -190,6 +200,33 @@ func tokenize(input string) ([]token, error) {
 		case ch == '\\':
 			startRaw(i)
 			escaped = true
 		case isSubstStart(input, i):
 			startRaw(i)
 			end := substEnd(input, i)
 			if end < 0 {
 				return nil, errors.New("missing ) in command substitution")
 			}
 			out, err := commandSubst(input[i+2 : end])
 			if err != nil {
 				return nil, err
 			}
 			if quote == '"' || assign {
 				// Quoted or in an assignment, the output is one word
 				literal(out)
 				inWord = true
 			} else {
 				// Unquoted, the output is split into words at blanks and
 				// newlines (but, unlike in sh, wildcards in it are not
 				// expanded)
 				for k, field := range strings.Fields(out) {
 					if k > 0 {
 						endWord()
 					}
 					literal(field)
 					inWord = true
 				}
 			}
 			i = end
 		case ch == '$':
 			startRaw(i)
 			value, n, err := expandVar(input[i:])
@@ -213,6 +250,7 @@ func tokenize(input string) ([]token, error) {
 			}
 		case ch == '"' || ch == '\'':
 			startRaw(i)
 			plain = false
 			quote = ch
 			inWord = true
 		case ch == ' ' || ch == '\t' || ch == '\n':
@@ -268,8 +306,8 @@ func tokenize(input string) ([]token, error) {
 				i = j - 1
 			}
 			tokens = append(tokens, t)
-		case ch == '~' && !inWord && b.Len() == 0 &&
+		case ch == '~' && (!inWord && b.Len() == 0 || afterAssignSep) &&
-			(i+1 == len(input) || strings.IndexByte("/ \t\n|<>", input[i+1]) >= 0):
+			(i+1 == len(input) || strings.IndexByte("/ \t\n|<>:", input[i+1]) >= 0):
 			startRaw(i)
 			home := getHomeDir()
 			if home == "" {
@@ -279,6 +317,14 @@ func tokenize(input string) ([]token, error) {
 			inWord = true
 		default:
 			startRaw(i)
 			switch {
 			case ch == '=' && plain && !assign && isVarName(b.String()):
 				// name=value; ~ may follow
 				assign, tildeOK = true, true
 			case ch == ':' && assign:
 				// PATH=~/bin:~/go/bin
 				tildeOK = true
 			}
 			b.WriteByte(ch)
 			switch {
 			case ch == '*' || ch == '?' || ch == '[':
@@ -714,7 +760,7 @@ type shellCompleter struct {
 func newShellCompleter() *shellCompleter {
 	return &shellCompleter{
-		commands: []string{"cd", "pwd", "echo", "exit", "quit", "set", "export", "source", "jobs", "fg", "bg", "wait", "alias", "unalias", "help"},
+		commands: []string{"cd", "pwd", "echo", "exit", "quit", "set", "export", "source", "jobs", "fg", "bg", "wait", "alias", "unalias", "break", "continue", "unset", "help"},
 	}
 }
@@ -728,6 +774,13 @@ func (c *shellCompleter) Do(line []rune, pos int) ([][]rune, int) {
 	before := strings.TrimSpace(string(line[:start]))
 	isFirstWord := before == "" || strings.HasSuffix(before, "|") ||
 		strings.HasSuffix(before, ";") || strings.HasSuffix(before, "&&")
 	// ... and after if, then, do etc.
 	if fields := strings.Fields(before); len(fields) > 0 {
 		switch fields[len(fields)-1] {
 		case "if", "then", "elif", "else", "do", "while", "until", "!":
 			isFirstWord = true
 		}
 	}
 	// Plain "~" -> "~/"
 	if word == "~" {
@@ -1042,28 +1095,56 @@ func sourceFile(cmd, path string) error {
 	return nil
 }
-// runScript executes the commands from r line by line. Like sh, it does not
+// runScript executes the commands from r. Each command is executed as soon
-// stop at a failing command and returns the exit status of the last one.
+// as it is complete (a control structure can span several lines). Like sh,
-// Empty lines and lines starting with # (e.g. a #!/usr/bin/gosh line) are
+// it does not stop at a failing command and returns the exit status of the
-// skipped. If name is set, errors are reported with file name and line.
+// last one. If name is set, errors are reported with file name and line.
 func runScript(r io.Reader, name string) int {
-	status := 0
+	var (
 		buf       strings.Builder
 		startLine int
 	)
 	report := func(err error, line int) {
 		if name != "" && err != nil {
 			err = fmt.Errorf("%s:%d: %w", sanitize(name), line, err)
 		}
 		printError(err)
 	}
 	for lineNo := 1; ; lineNo++ {
-		line, err := readLine(r)
+		line, readErr := readLine(r)
-		if trimmed := strings.TrimSpace(line); trimmed != "" && !strings.HasPrefix(trimmed, "#") {
+		if readErr == nil || line != "" {
-			cmdErr := execInput(line)
+			if buf.Len() == 0 {
-			status = lastStatus
+				if strings.TrimSpace(line) == "" {
-			if name != "" && cmdErr != nil {
+					goto next
 				cmdErr = fmt.Errorf("%s:%d: %w", sanitize(name), lineNo, cmdErr)
 				}
-			printError(cmdErr)
+				startLine = lineNo
 			}
 			buf.WriteString(line)
 			buf.WriteByte('\n')
 			tree, err := parse(buf.String())
 			if errors.Is(err, errIncomplete) {
 				goto next // read the rest of the command
 			}
 			buf.Reset()
 			if err != nil {
-			if err != io.EOF {
+				lastStatus = exitStatus(err)
-				fmt.Fprintln(os.Stderr, "gosh:", err)
+				report(err, startLine)
 			} else {
 				report(tree.exec(), startLine)
 			}
 		}
 	next:
 		if readErr != nil {
 			if readErr != io.EOF {
 				fmt.Fprintln(os.Stderr, "gosh:", readErr)
 				return 1
 			}
-			return status
+			if buf.Len() > 0 {
 				lastStatus = 2
 				report(errors.New("syntax error: unexpected end of file"), startLine)
 			}
 			return lastStatus
 		}
 	}
 }
@@ -1101,10 +1182,16 @@ func exitStatus(err error) int {
 	if errors.As(err, &statusErr) {
 		return int(statusErr)
 	}
-	var synErr syntaxError
+	var (
-	if errors.As(err, &synErr) {
+		synErr syntaxError
 		lc     loopControl
 	)
 	if errors.As(err, &synErr) || errors.Is(err, errIncomplete) {
 		return 2
 	}
 	if errors.As(err, &lc) {
 		return 0
 	}
 	var exitErr *exec.ExitError
 	if errors.As(err, &exitErr) {
 		if ws, ok := exitErr.Sys().(syscall.WaitStatus); ok && ws.Signaled() {
@@ -1156,23 +1243,35 @@ func interactive() {
 	}
 	defer l.Close()
-	// Main loop
+	// Main loop. A command that is not complete yet (e.g. if without fi)
 	// is continued on the next line with the prompt "> ".
 	var buf strings.Builder
 	for {
 		if buf.Len() == 0 {
 			// Report finished and stopped background jobs
 			reapJobs(true)
 			// Update prompt dynamically (in case directory changed)
 			l.SetPrompt(getPrompt())
 		} else {
 			l.SetPrompt("> ")
 		}
 		line, err := l.Readline()
 		if err != nil {
-			// Ctrl+C discards the current line
+			// Ctrl+C discards the current line (and an incomplete command)
 			if err == readline.ErrInterrupt {
 				buf.Reset()
 				continue
 			}
 			// Handle EOF (Ctrl+D)
 			if err == io.EOF {
 				fmt.Println()
 				if buf.Len() > 0 {
 					buf.Reset()
 					lastStatus = 2
 					fmt.Fprintln(os.Stderr, "gosh: syntax error: unexpected end of file")
 					continue
 				}
 				if hasStoppedJobs() && !exitWarned {
 					exitWarned = true
 					fmt.Fprintln(os.Stderr, "gosh: there are stopped jobs")
@@ -1185,7 +1284,7 @@ func interactive() {
 		}
 		// Skip empty input
-		if strings.TrimSpace(line) == "" {
+		if buf.Len() == 0 && strings.TrimSpace(line) == "" {
 			continue
 		}
@@ -1195,8 +1294,19 @@ func interactive() {
 			l.SaveHistory(line)
 		}
-		// Execute the input
+		buf.WriteString(line)
-		printError(execInput(line))
+		buf.WriteByte('\n')
 		tree, err := parse(buf.String())
 		if errors.Is(err, errIncomplete) {
 			continue
 		}
 		buf.Reset()
 		if err != nil {
 			lastStatus = exitStatus(err)
 			printError(err)
 			continue
 		}
 		printError(tree.exec())
 	}
 }
@@ -1228,145 +1338,31 @@ func printError(err error) {
 	var (
 		exitErr   *exec.ExitError
 		statusErr statusError
 		lc        loopControl
 	)
-	if err == nil || errors.As(err, &exitErr) || errors.As(err, &statusErr) {
+	if err == nil || errors.As(err, &exitErr) || errors.As(err, &statusErr) || errors.As(err, &lc) {
 		return
 	}
 	fmt.Fprintln(os.Stderr, "gosh:", err)
 }
-// listItem is a command of a command list together with the operator that
+// execInput parses and executes input: a command line or a whole script.
-// connects it to the previous command ("" for the first one).
+// It returns the error of the last command that was run; errors of earlier
-type listItem struct {
+// commands are printed. $? is updated after each command.
 	op         string // "", ";", "&&" or "||"
 	command    string
 	background bool // the command ends with &
 }
 // 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 $PWD" works.
 func splitList(input string) ([]listItem, error) {
 	var (
 		items     []listItem
 		op        string
 		start     int
 		quote     byte
 		escaped   bool
 		wordStart = true // the next character starts a word
 	)
 	end := len(input)
 	add := func(i int, next string) error {
 		command := input[start:i]
 		if strings.TrimSpace(command) == "" {
 			// "a;" is fine, but an operator needs a command on both sides
 			if next != "" || op == "&&" || op == "||" {
 				if next == "" {
 					next = op
 				}
 				return syntaxError(next)
 			}
 			return nil
 		}
 		items = append(items, listItem{op: op, command: command})
 		return nil
 	}
 scan:
 	for i := 0; i < len(input); i++ {
 		ch := input[i]
 		isWordStart := wordStart
 		wordStart = false
 		switch {
 		case escaped:
 			escaped = false
 		case quote == '\'':
 			if ch == '\'' {
 				quote = 0
 			}
 		case ch == '\\':
 			escaped = true
 		case ch == '$' && 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 == '&' && !(i+1 < len(input) && strings.IndexByte("&>", input[i+1]) >= 0) &&
 			!(i > 0 && strings.IndexByte("<>", input[i-1]) >= 0):
 			// A single & (not &&, &>, >& or <&) runs the command in the
 			// background
 			if err := add(i, "&"); err != nil {
 				return nil, err
 			}
 			items[len(items)-1].background = true
 			op = ";"
 			start = i + 1
 			wordStart = true
 		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 {
-	if interactiveShell {
+	tree, err := parse(input)
 		input = expandAliases(input)
 	}
 	items, err := splitList(input)
 	if err != nil {
 		lastStatus = exitStatus(err)
 		return err
 	}
-
+	return tree.exec()
 	var lastErr error
 	for _, item := range items {
 		if (item.op == "&&" && lastStatus != 0) || (item.op == "||" && lastStatus == 0) {
 			continue
 		}
 		printError(lastErr)
 		lastErr = execCommand(item.command, item.background)
 		lastStatus = exitStatus(lastErr)
 	}
 	return lastErr
 }
 // execCommand executes a pipeline of simple commands with redirections, in
 // the background if background is set.
 func execCommand(input string, background bool) error {
 	// Brace expansion comes first, so that its results are expanded further
 	substStatus = 0
 	input, err := expandBraceWords(input)
 	if err != nil {
 		return err
@@ -1375,8 +1371,11 @@ func execCommand(input string, background bool) error {
 	// Split the input into words and operators, expanding variables and ~ on
 	// the way.
 	tokens, err := tokenize(input)
-	var synErr syntaxError
+	var (
-	if errors.As(err, &synErr) {
+		synErr    syntaxError
 		statusErr statusError
 	)
 	if errors.As(err, &synErr) || errors.As(err, &statusErr) {
 		return err
 	}
 	if err != nil {
@@ -1387,6 +1386,10 @@ func execCommand(input string, background bool) error {
 		return err
 	}
 	if len(stages) == 0 {
 		// A command that consists only of $(...) has its status
 		if substStatus != 0 {
 			return statusError(substStatus)
 		}
 		return nil
 	}
 	// "exit" with stopped jobs only warns, unless it is repeated right away
@@ -1406,6 +1409,7 @@ type redirect struct {
 // stage is a simple command of a pipeline.
 type stage struct {
 	assigns   []string // name=value before the command name
 	args      []string
 	redirects []redirect
 }
@@ -1416,13 +1420,18 @@ func parsePipeline(tokens []token) ([]stage, error) {
 		stages []stage
 		cur    stage
 	)
-	isEmpty := func(s stage) bool { return len(s.args) == 0 && len(s.redirects) == 0 }
+	isEmpty := func(s stage) bool { return len(s.assigns) == 0 && len(s.args) == 0 && len(s.redirects) == 0 }
 	for i := 0; i < len(tokens); i++ {
 		t := tokens[i]
 		switch t.op {
 		case "":
 			if t.assign && len(cur.args) == 0 {
 				// The value is not split and not expanded as a pattern
 				cur.assigns = append(cur.assigns, t.word)
 			} else {
 				cur.args = append(cur.args, expandWord(t)...)
 			}
 		case "|":
 			if isEmpty(cur) {
 				return nil, syntaxError("|")
@@ -1541,6 +1550,20 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
 	fds := [3]*os.File{stdin, stdout, os.Stderr}
 	opened, err := applyRedirects(&fds, st.redirects)
 	owned = append(owned, opened...)
 	if err == nil && len(st.args) == 0 && len(st.assigns) > 0 {
 		// Assignments without a command set variables of the shell (not in
 		// a pipeline or in the background, where sh runs them in a
 		// subshell). The status is the one of the last $(...) in them.
 		if !inPipeline && !background {
 			for _, a := range st.assigns {
 				name, value, _ := strings.Cut(a, "=")
 				os.Setenv(name, value)
 			}
 		}
 		if substStatus != 0 {
 			err = statusError(substStatus)
 		}
 	}
 	if err != nil || len(st.args) == 0 {
 		// A command without arguments only creates or truncates the files
 		closeOwned()
@@ -1567,6 +1590,8 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
 			return err
 		}
 		if !inPipeline && !background {
 			// name=value before a builtin applies only while it runs
 			defer setTemporarily(st.assigns)()
 			return finishedProc(run())
 		}
 		p := &proc{done: make(chan error, 1)}
@@ -1576,6 +1601,11 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
 	cmd := exec.Command(st.args[0], st.args[1:]...)
 	cmd.Stdin, cmd.Stdout, cmd.Stderr = fds[0], fds[1], fds[2]
 	if len(st.assigns) > 0 {
 		// name=value before a command is only in its environment (the
 		// last value of a name wins)
 		cmd.Env = append(os.Environ(), st.assigns...)
 	}
 	if jobControl {
 		// All processes of the job share a process group: the one of the
 		// first process. In the foreground, the first process makes its
@@ -1608,6 +1638,31 @@ func startStage(st stage, stdin, stdout *os.File, j *job, inPipeline, background
 	return &proc{cmd: cmd}
 }
 // setTemporarily sets the variables of the assignments and returns a
 // function that restores the previous values.
 func setTemporarily(assigns []string) func() {
 	type saved struct {
 		name, value string
 		ok          bool
 	}
 	var restore []saved
 	for _, a := range assigns {
 		name, value, _ := strings.Cut(a, "=")
 		old, ok := os.LookupEnv(name)
 		restore = append(restore, saved{name, old, ok})
 		os.Setenv(name, value)
 	}
 	return func() {
 		for i := len(restore) - 1; i >= 0; i-- {
 			if r := restore[i]; r.ok {
 				os.Setenv(r.name, r.value)
 			} else {
 				os.Unsetenv(r.name)
 			}
 		}
 	}
 }
 // applyRedirects applies the redirections in order to fds (stdin, stdout,
 // stderr) and returns the files it opened.
 func applyRedirects(fds *[3]*os.File, redirects []redirect) ([]*os.File, error) {
@@ -1675,6 +1730,10 @@ var builtins = map[string]struct{ changesState bool }{
 	"wait":     {changesState: true},
 	"alias":    {},
 	"unalias":  {changesState: true},
 	":":        {},
 	"unset":    {changesState: true},
 	"break":    {changesState: true},
 	"continue": {changesState: true},
 }
 // runBuiltin executes a built-in command, writing its output to stdout.
@@ -1754,6 +1813,25 @@ func runBuiltin(args []string, stdout io.Writer) error {
 		}
 		os.Setenv(parts[0], parts[1])
 		return nil
 	case ":":
 		// Does nothing, successfully (e.g. while :; do ...)
 		return nil
 	case "unset":
 		// unset NAME ... - remove variables
 		if len(args) < 2 {
 			return fmt.Errorf("usage: unset NAME ...")
 		}
 		var err error
 		for _, name := range args[1:] {
 			if !isVarName(name) {
 				err = fmt.Errorf("unset: `%s': not a valid identifier", sanitize(name))
 				continue
 			}
 			os.Unsetenv(name)
 		}
 		return err
 	case "break", "continue":
 		return builtinLoopControl(args)
 	case "alias":
 		return builtinAlias(args, stdout)
 	case "unalias":
@@ -1783,6 +1861,7 @@ Built-in commands:
  quit [code]   - Quit shell with status code (default: $?)
  set VAR=val   - Set environment variable
  export VAR=val - Export environment variable
  unset VAR     - Remove a variable
  source file   - Run the commands of file in this shell (also: . file)
  jobs          - List background and stopped jobs
  fg [%n]       - Continue job n (default: current job) in the foreground
@@ -1790,6 +1869,9 @@ Built-in commands:
  wait [%n]     - Wait for job n or all background jobs
  alias [name[=value] ...] - Define or show aliases (alias ll='ls -l')
  unalias name  - Remove an alias (unalias -a: all aliases)
  :             - Do nothing (exit status 0)
  break [n]     - Leave the innermost (or n-th) for/while/until loop
  continue [n]  - Continue with the next iteration of a loop
  help          - Show this help
 Features:
@@ -1812,10 +1894,19 @@ Features:
    GOSH_COLORS='user=1;33:path=36' (keys user, root, path, error; values
    are ANSI SGR codes, empty = no color); disabled with $NO_COLOR,
    TERM=dumb or when output is not a terminal
  - Variables: name=value sets a variable (like set), name=value command
    sets it only for that command; the value is not split or expanded as
    a pattern
  - Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
    using an unset variable is an error, use ${VAR:-} for an empty default
  - Command substitution: $(command) is replaced by the output of command
    (run in a subshell); unquoted it is split into words, "$(command)"
    stays one word
  - 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
  - Control structures: if cmd; then ...; elif cmd; then ...; else ...; fi,
    for x in words; do ...; done, while cmd; do ...; done, until ...,
    ! cmd negates the status; they can span several lines (prompt "> ")
  - Pipes (a | b) and redirections: < file, > file, >> file, 2> file,
    2>> file, 2>&1, >&2, &> file (stdout and stderr), &>> file
  - Job control: command & runs in the background, Ctrl+Z stops the
@@ -3,6 +3,7 @@ package main
 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"os"
 	"os/exec"
@@ -841,7 +842,7 @@ func TestShellCompleter_Do(t *testing.T) {
 		want   []string
 		length int
 	}{
-		{"c", []string{"d "}, 1},
+		{"c", []string{"d ", "ontinue "}, 1},
 		{"e", []string{"cho ", "xit ", "xport "}, 1},
 		{"gi", []string{"tty "}, 2},
 		{"  gi", []string{"tty "}, 2},
@@ -892,6 +893,11 @@ func TestMain(m *testing.M) {
 	// Never read the system's startup files; tests that read the user's
 	// files set $HOME themselves
 	sysConfDir = filepath.Join(dir, "etc")
 	// Command substitution runs gosh, not the test binary
 	subshellPath = filepath.Join(dir, "gosh")
 	if out, err := exec.Command("go", "build", "-o", subshellPath, ".").CombinedOutput(); err != nil {
 		panic(fmt.Sprintf("building gosh: %v\n%s", err, out))
 	}
 	code := m.Run()
 	os.RemoveAll(dir)
 	os.Exit(code)
@@ -1381,48 +1387,170 @@ func TestReadLine_DoesNotReadAhead(t *testing.T) {
 	}
 }
-func TestSplitList(t *testing.T) {
+// treeString formats a syntax tree for the tests: simple commands in
 // brackets, background commands with a trailing &.
 func treeString(l *listNode) string {
 	var parts []string
 	for _, e := range l.items {
 		s := pipelineString(e.andOr.first)
 		for _, r := range e.andOr.rest {
 			s += " " + r.op + " " + pipelineString(r.pipeline)
 		}
 		if e.background {
 			s += " &"
 		}
 		parts = append(parts, s)
 	}
 	return strings.Join(parts, "; ")
 }
 func pipelineString(pl *pipelineNode) string {
 	s := ""
 	if pl.negate {
 		s = "! "
 	}
 	switch n := pl.cmd.(type) {
 	case *simpleNode:
 		s += "[" + n.text + "]"
 	case *ifNode:
 		s += "if"
 		for i := range n.conds {
 			if i > 0 {
 				s += " elif"
 			}
 			s += " " + treeString(n.conds[i]) + " then " + treeString(n.bodies[i])
 		}
 		if n.elseBody != nil {
 			s += " else " + treeString(n.elseBody)
 		}
 		s += " fi"
 	case *forNode:
 		s += "for " + n.name
 		if n.hasIn {
 			s += " in (" + n.words + ")"
 		}
 		s += " do " + treeString(n.body) + " done"
 	case *whileNode:
 		if n.until {
 			s += "until "
 		} else {
 			s += "while "
 		}
 		s += treeString(n.cond) + " do " + treeString(n.body) + " done"
 	}
 	return s
 }
 func TestParse_Lists(t *testing.T) {
 	tests := []struct {
 		input string
-		want  []listItem
+		want  string
 	}{
-		{"", nil},
+		{"", ""},
-		{"   ", nil},
+		{"   ", ""},
-		{"# only a comment", nil},
+		{"# only a comment", ""},
-		{"ls", []listItem{{"", "ls", false}}},
+		{"ls", "[ls]"},
-		{"a; b", []listItem{{"", "a", false}, {";", " b", false}}},
+		{"a; b", "[a]; [b]"},
-		{"a;", []listItem{{"", "a", false}}},
+		{"a;", "[a]"},
-		{"a && b || c", []listItem{{"", "a ", false}, {"&&", " b ", false}, {"||", " c", false}}},
+		{"a\nb\n", "[a]; [b]"},
-		{`echo "a;b" 'c&&d' e\;f`, []listItem{{"", `echo "a;b" 'c&&d' e\;f`, false}}},
+		{"a && b || c", "[a] && [b] || [c]"},
-		{`echo "x\"; y"`, []listItem{{"", `echo "x\"; y"`, false}}},
+		{"a &&\n  b", "[a] && [b]"},
-		{"echo ${X:-a;b}; c", []listItem{{"", "echo ${X:-a;b}", false}, {";", " c", false}}},
+		{"a | b|c", "[a | b|c]"},
-		{"echo a # b; c", []listItem{{"", "echo a ", false}}},
+		{"a |\n b", "[a |\n b]"},
-		{"echo a#b; c", []listItem{{"", "echo a#b", false}, {";", " c", false}}},
+		{`echo "a;b" 'c&&d' e\;f`, `[echo "a;b" 'c&&d' e\;f]`},
-		{"echo a|b", []listItem{{"", "echo a|b", false}}},
+		{`echo "x\"; y"`, `[echo "x\"; y"]`},
-		{"a & b", []listItem{{"", "a ", true}, {";", " b", false}}},
+		{"echo ${X:-a;b}; c", "[echo ${X:-a;b}]; [c]"},
-		{"a &", []listItem{{"", "a ", true}}},
+		{"echo a # b; c", "[echo a]"},
-		{"a&", []listItem{{"", "a", true}}},
+		{"echo a#b; c", "[echo a#b]; [c]"},
-		{"a 2>&1 &", []listItem{{"", "a 2>&1 ", true}}},
+		{"a & b", "[a] &; [b]"},
-		{"a &> f &", []listItem{{"", "a &> f ", true}}},
+		{"a&", "[a] &"},
-		{"a >&2 && b", []listItem{{"", "a >&2 ", false}, {"&&", " b", false}}},
+		{"a 2>&1 &", "[a 2>&1] &"},
-		{`echo "a & b" \&`, []listItem{{"", `echo "a & b" \&`, false}}},
+		{"a &> f &", "[a &> f] &"},
 		{"a >&2 && b", "[a >&2] && [b]"},
 		{`echo "a & b" \&`, `[echo "a & b" \&]`},
 		{"echo $(a; b && c | d) \"$(e || f)\" & g", `[echo $(a; b && c | d) "$(e || f)"] &; [g]`},
 		{"! false", "! [false]"},
 		{"echo a \\\n b", "[echo a  b]"},
 		// Reserved words are only special as the first word of a command
 		{"echo if then fi do done", "[echo if then fi do done]"},
 	}
 	for _, tc := range tests {
-		got, err := splitList(tc.input)
+		tree, err := parse(tc.input)
 		if err != nil {
-			t.Errorf("splitList(%q) returned error: %v", tc.input, err)
+			t.Errorf("parse(%q) returned error: %v", tc.input, err)
 			continue
 		}
-		if !reflect.DeepEqual(got, tc.want) {
+		if got := treeString(tree); got != tc.want {
-			t.Errorf("splitList(%q) = %+v, want %+v", tc.input, got, tc.want)
+			t.Errorf("parse(%q) = %s, want %s", tc.input, got, tc.want)
 		}
 	}
 }
-func TestSplitList_SyntaxErrors(t *testing.T) {
+func TestParse_ControlStructures(t *testing.T) {
-	for _, input := range []string{"; a", "a ;; b", "&& a", "a &&", "a ||", "a && ; b", "a || && b", "& a", "a & && b", "a & & b"} {
+	tests := []struct {
-		if _, err := splitList(input); err == nil || !strings.Contains(err.Error(), "syntax error") {
+		input string
-			t.Errorf("splitList(%q) = %v, want syntax error", input, err)
+		want  string
 	}{
 		{"if a; then b; fi", "if [a] then [b] fi"},
 		{"if a\nthen\n  b\n  c\nfi", "if [a] then [b]; [c] fi"},
 		{"if a; then b; elif c; then d; else e; fi", "if [a] then [b] elif [c] then [d] else [e] fi"},
 		{"if a && ! b; then c; fi; echo x", "if [a] && ! [b] then [c] fi; [echo x]"},
 		{"for x in a b c; do echo $x; done", "for x in (a b c) do [echo $x] done"},
 		{"for x in *.go {1..3}\ndo\n  echo $x\ndone", "for x in (*.go {1..3}) do [echo $x] done"},
 		{"for x; do echo; done", "for x do [echo] done"},
 		{"for x in; do echo; done", "for x in () do [echo] done"},
 		{"while a; do b; done", "while [a] do [b] done"},
 		{"until a; do b; done", "until [a] do [b] done"},
 		{"while a; do if b; then break; fi; done", "while [a] do if [b] then [break] fi done"},
 		{"for i in 1 2; do for j in 3 4; do echo $i$j; done; done", "for i in (1 2) do for j in (3 4) do [echo $i$j] done done"},
 		{"if a; then if b; then c; fi fi", "if [a] then if [b] then [c] fi fi"},
 	}
 	for _, tc := range tests {
 		tree, err := parse(tc.input)
 		if err != nil {
 			t.Errorf("parse(%q) returned error: %v", tc.input, err)
 			continue
 		}
 		if got := treeString(tree); got != tc.want {
 			t.Errorf("parse(%q) = %s, want %s", tc.input, got, tc.want)
 		}
 	}
 }
 func TestParse_Incomplete(t *testing.T) {
 	for _, input := range []string{
 		"if a", "if a; then", "if a; then b", "if a; then b; else", "if a; then b; elif c",
 		"for x", "for x in a b", "for x in a; do", "for x in a; do b",
 		"while a", "while a; do b", "until a; do",
 		"a &&", "a ||", "a |", "echo 'open", `echo "open`, "echo $(a", "echo a \\",
 	} {
 		if _, err := parse(input); !errors.Is(err, errIncomplete) {
 			t.Errorf("parse(%q) = %v, want incomplete", input, err)
 		}
 	}
 }
 func TestParse_SyntaxErrors(t *testing.T) {
 	for _, input := range []string{
 		"; a", "a ;; b", "&& a", "a && ; b", "a || && b", "& a", "a & && b", "a & & b",
 		"fi", "then", "done", "if a; then fi", "if ; then a; fi", "while a; do done",
 		"if a; then b; done", "for 1x in a; do b; done", "for x in a do b; done; x",
 		"a | | b", "| a",
 	} {
 		_, err := parse(input)
 		if err == nil || errors.Is(err, errIncomplete) {
 			t.Errorf("parse(%q) = %v, want syntax error", input, err)
 		}
 	}
 	for input, want := range map[string]string{
 		"for x in a; do b; done | cat": "control structures in pipelines are not supported",
 		"echo | while a; do b; done":   "control structures in pipelines are not supported",
 		"if a; then b; fi > out":       "redirections of control structures are not supported (near `>')",
 		"for x in a; do b; done &":     "only simple commands and pipelines can run in the background",
 		"a && b &":                     "only simple commands and pipelines can run in the background",
 	} {
 		if _, err := parse(input); err == nil || err.Error() != want {
 			t.Errorf("parse(%q) = %v, want %q", input, err, want)
 		}
 	}
 }
@@ -1546,7 +1674,7 @@ func TestTokenize_Operators(t *testing.T) {
 		}
 		// Patterns are tested in TestTokenize_Patterns
 		for i := range got {
-			got[i].pattern, got[i].glob = "", false
+			got[i].pattern, got[i].glob, got[i].assign = "", false, false
 		}
 		if !reflect.DeepEqual(got, tc.want) {
 			t.Errorf("tokenize(%q) = %+v, want %+v", tc.input, got, tc.want)
@@ -0,0 +1,504 @@
 .\" Man page for gosh. View with: man ./packaging/man/gosh.1
 .\" @VERSION@ is replaced by the release version when building packages.
 .TH GOSH 1 "October 2026" "gosh @VERSION@" "User Commands"
 .SH NAME
 gosh \- a simple shell written in Go
 .SH SYNOPSIS
 .B gosh
 .RB [ \-l ]
 .RB [ \-i ]
 .RB [ \-\-norc ]
 .RB [ \-\-noprofile ]
 .RI [ script ]
 .br
 .B gosh
 .RB [ \-l ]
 .RB [ \-\-noprofile ]
 .B \-c
 .I command
 .br
 .B gosh
 .B \-version
 .SH DESCRIPTION
 .B gosh
 is a small command interpreter with a syntax close to
 .BR sh (1).
 It supports command history, tab completion, variables, command
 substitution, command lists, control structures, pipes, redirections,
 wildcards, brace expansion, aliases and job control.
 .PP
 Without arguments and with a terminal on standard input,
 .B gosh
 starts an interactive shell. With a
 .I script
 argument it runs the commands of that file, with
 .B \-c
 the given command string, and otherwise it reads commands from standard
 input.
 .PP
 .B gosh
 is a proof of concept and not meant for production use.
 .SH OPTIONS
 .TP
 .B \-c \fIcommand\fP
 Run
 .I command
 and exit.
 .TP
 .B \-i
 Force interactive mode, even if standard input is not a terminal.
 .TP
 .BR \-l ", " \-\-login
 Act as a login shell and read the profile files (see
 .BR "STARTUP FILES" ).
 A shell whose
 .I argv[0]
 starts with
 .B \-
 (as started by
 .BR login (1),
 .BR sshd (8)
 or
 .BR "su \-" )
 is a login shell as well.
 .TP
 .B \-\-norc
 Do not read the goshrc files.
 .TP
 .B \-\-noprofile
 Do not read the profile files.
 .TP
 .BR \-version ", " \-\-version ", " \-V
 Print the version, branch and commit and exit.
 .TP
 .BR \-h ", " \-\-help
 Print a usage summary and exit.
 .TP
 .B \-
 Read commands from standard input.
 .SH NON-INTERACTIVE USE
 Scripts, command strings and commands read from a pipe are executed line
 by line. Empty lines and lines starting with
 .B #
 are skipped, so a script may start with
 .BR "#!/usr/bin/gosh" .
 A failing command does not abort the script; the exit status of
 .B gosh
 is the one of the last command.
 .PP
 Because
 .B gosh
 supports
 .BR \-c ,
 .BR ssh (1),
 .BR scp (1)
 and
 .BR rsync (1)
 work when it is used as login shell.
 .SH STARTUP FILES
 Startup files are executed in the running shell, so variables and
 aliases defined there stay in effect.
 .TP
 Login shells
 read
 .I /etc/gosh/profile
 and
 .IR ~/.gosh_profile .
 .TP
 Interactive shells
 read
 .I /etc/gosh/goshrc
 and
 .IR ~/.goshrc .
 .PP
 An interactive login shell reads the profile files first, then the goshrc
 files. Scripts and
 .B \-c
 read no startup files unless
 .B gosh
 is a login shell. Missing files are skipped; errors are reported with file
 name and line number and the remaining lines still run. Files of other
 shells such as
 .I /etc/profile
 or
 .I ~/.bashrc
 are not read.
 .SH SYNTAX
 .SS Quoting
 .TP
 .B \(aq...\(aq
 Everything is literal.
 .TP
 .B \(dq...\(dq
 Variables and command substitutions are expanded, the result stays one
 word.
 .TP
 .B \e
 Escapes the next character.
 .SS Variables
 .TP
 .I name\fB=\fPvalue
 Set a variable. All variables are exported to the environment of started
 programs. The value is not split into words and not expanded as a pattern;
 variables, command substitutions and
 .B ~
 (at the start, after
 .B =
 and after
 .BR : )
 are expanded.
 .TP
 .I name\fB=\fPvalue command
 Set the variable only for
 .IR command .
 .TP
 .BR $VAR ", " ${VAR}
 The value of
 .BR VAR .
 Using an unset variable is an error and aborts the command.
 .TP
 .B ${VAR:\-default}
 The value of
 .BR VAR ,
 or
 .I default
 if it is unset or empty. Use
 .B ${VAR:\-}
 for an empty default.
 .TP
 .B $?
 The exit status of the last command.
 .SS Command substitution
 .B $(\fIcommand\fP)
 is replaced by the output of
 .IR command ,
 which runs in a subshell. Trailing newlines are removed. Unquoted, the
 output is split into words at blanks and newlines; inside double quotes it
 stays one word. Wildcards and operators in the output are not interpreted.
 Backticks and arithmetic expansion are not supported.
 .SS Tilde and brace expansion
 .B ~
 and
 .B ~/path
 at the start of an unquoted word are replaced by the home directory.
 .PP
 Brace expansion generates several words from one:
 .B a{b,c}d
 becomes
 .BR "abd acd" ,
 .B {1..5}
 becomes
 .BR "1 2 3 4 5" ,
 .B {01..10..4}
 becomes
 .B 01 05 09
 and
 .B {a..e}
 becomes
 .BR "a b c d e" .
 Brace expansion happens before all other expansions.
 .SS Wildcards
 .B *
 matches any string,
 .B ?
 any single character,
 .B [abc]
 and
 .B [a\-z]
 one of the given characters and
 .B [!abc]
 (or
 .BR [^abc] )
 any character except those. Matches are sorted. Hidden files are only
 matched if the pattern starts with a dot. A pattern without match is kept
 unchanged. Quoted wildcards and values of variables are never expanded.
 .SS Command lists
 .TP
 .IB a " ; " b
 Run
 .IR a ,
 then
 .IR b .
 .TP
 .IB a " && " b
 Run
 .I b
 only if
 .I a
 succeeded.
 .TP
 .IB a " || " b
 Run
 .I b
 only if
 .I a
 failed.
 .TP
 .IB command " &"
 Run
 .I command
 in the background.
 .SS Pipes and redirections
 .TP
 .IB a " | " b
 Connect standard output of
 .I a
 to standard input of
 .IR b .
 The exit status is the one of
 .IR b .
 .TP
 .BI < " file"
 Read standard input from
 .IR file .
 .TP
 .BR > " \fIfile\fP, " >> " \fIfile\fP"
 Write (or append) standard output to
 .IR file .
 .TP
 .BR 2> " \fIfile\fP, " 2>> " \fIfile\fP"
 Write (or append) standard error to
 .IR file .
 .TP
 .B 2>&1
 Redirect standard error to where standard output goes.
 .TP
 .B >&2
 Redirect standard output to where standard error goes.
 .TP
 .BR &> " \fIfile\fP, " &>> " \fIfile\fP"
 Write (or append) standard output and standard error to
 .IR file .
 .PP
 Redirections are evaluated from left to right. Only file descriptors 0, 1
 and 2 are supported.
 .SS Control structures
 .nf
 \fBif\fP \fIlist\fP; \fBthen\fP \fIlist\fP; [\fBelif\fP \fIlist\fP; \fBthen\fP \fIlist\fP;] [\fBelse\fP \fIlist\fP;] \fBfi\fP
 \fBfor\fP \fIname\fP \fBin\fP \fIwords\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
 \fBwhile\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
 \fBuntil\fP \fIlist\fP; \fBdo\fP \fIlist\fP; \fBdone\fP
 \fB!\fP \fIcommand\fP
 .fi
 .PP
 Control structures may span several lines; an incomplete command shows
 the continuation prompt
 .BR "> " .
 .B !
 negates the exit status of a command. Control structures cannot be used
 in pipes, with redirections or in the background.
 .B case
 and functions are not supported.
 .SS Aliases
 In interactive shells, the first word of a command is replaced by its
 alias. If the alias value ends with a blank, the next word is checked for
 an alias as well.
 .B \e\fIname\fP
 or
 .B \(aq\fIname\fP\(aq
 skips the alias. Aliases are not used in scripts and with
 .BR \-c .
 .SH BUILTIN COMMANDS
 .TP
 .BR cd " [\fIdir\fP]"
 Change the directory; without argument to the home directory.
 .TP
 .B pwd
 Print the working directory.
 .TP
 .BR echo " [\fIargs\fP]"
 Print the arguments.
 .TP
 .BR exit " [\fIcode\fP], " quit " [\fIcode\fP]"
 Exit the shell with status
 .I code
 (default:
 .BR $? ).
 .TP
 .BI set " VAR" = value
 Set a variable.
 .TP
 .BI export " VAR" = value
 Export a variable.
 .TP
 .BI unset " VAR"
 Remove a variable.
 .TP
 .BI source " file\fR, \fP" ". " file
 Run the commands of
 .I file
 in the current shell.
 .TP
 .B jobs
 List background and stopped jobs.
 .TP
 .BR fg " [\fB%\fP\fIn\fP]"
 Continue job
 .I n
 (default: the current job) in the foreground.
 .TP
 .BR bg " [\fB%\fP\fIn\fP]"
 Continue stopped job
 .I n
 in the background.
 .TP
 .BR wait " [\fB%\fP\fIn\fP]"
 Wait for job
 .I n
 or for all background jobs.
 .TP
 .BR alias " [\fIname\fP[\fB=\fP\fIvalue\fP] ...]"
 Define or show aliases.
 .TP
 .BR unalias " \fIname\fP, " "unalias \-a"
 Remove an alias, or all aliases.
 .TP
 .B :
 Do nothing, exit status 0.
 .TP
 .BR break " [\fIn\fP], " continue " [\fIn\fP]"
 Leave the innermost (or
 .IR n -th)
 loop, or continue with its next iteration.
 .TP
 .B help
 Show a summary of builtins and features.
 .SH JOB CONTROL
 In interactive shells, each command line runs as a job in its own process
 group.
 .B Ctrl+Z
 stops the foreground job,
 .B Ctrl+C
 interrupts it.
 .BR jobs ,
 .BR fg ,
 .B bg
 and
 .B wait
 manage the jobs;
 .B %n
 or
 .I n
 refers to job
 .IR n ,
 .B %\-
 to the previous job. Finished background jobs are reported before the
 next prompt. Exiting with stopped jobs warns once.
 .SH INTERACTIVE USE
 .TP
 .B Up/Down
 Browse the command history.
 .TP
 .B Tab
 Complete commands, aliases and file names.
 .TP
 .B Ctrl+C
 Cancel the current line or command.
 .TP
 .B Ctrl+D
 Exit the shell.
 .PP
 Lines starting with a space are not saved in the history.
 .PP
 The prompt shows
 .IR user @ host : dir
 followed by
 .BR $ .
 If the last command failed, its exit status is shown as
 .BI [ N ]
 before the
 .BR $ .
 .SH ENVIRONMENT
 .TP
 .B GOSH_HISTFILE
 Path of the history file. If set to an empty value, no history is saved.
 .TP
 .B XDG_STATE_HOME
 Base directory of the default history file
 .IR $XDG_STATE_HOME/gosh/history .
 .TP
 .B GOSH_COLORS
 Prompt colors as colon-separated
 .IB key = code
 entries. Keys are
 .B user
 (default
 .BR 1;32 ),
 .B root
 .RB ( 1;31 ),
 .B path
 .RB ( 1;34 )
 and
 .B error
 .RB ( 1;31 );
 values are ANSI SGR codes, an empty value disables the color. Example:
 .B GOSH_COLORS=\(aquser=1;33:path=36\(aq
 .TP
 .B NO_COLOR
 If set, the prompt is not colored. Colors are also disabled with
 .B TERM=dumb
 or when the output is not a terminal.
 .TP
 .B HOME
 Used for
 .B ~
 and
 .B cd
 without argument.
 .TP
 .B PATH
 Directories searched for commands.
 .SH FILES
 .TP
 .I /etc/gosh/profile
 System-wide profile for login shells.
 .TP
 .I ~/.gosh_profile
 Personal profile for login shells.
 .TP
 .I /etc/gosh/goshrc
 System-wide startup file for interactive shells.
 .TP
 .I ~/.goshrc
 Personal startup file for interactive shells.
 .TP
 .I ~/.local/state/gosh/history
 Default history file (mode 0600).
 .SH EXIT STATUS
 The exit status of the last command, or the argument of
 .BR exit .
 Typical values:
 .TP
 .B 1
 General error.
 .TP
 .B 2
 Syntax error or invalid option.
 .TP
 .B 126
 Command not executable.
 .TP
 .B 127
 Command not found.
 .TP
 .BI 128+ n
 Command terminated by signal
 .I n
 (130 for Ctrl+C).
 .SH EXAMPLES
 .nf
 gosh \-c \(aqcd /srv && git log | head\(aq
 for f in *.log; do gzip "$f"; done
 cp config.yaml{,.bak}
 make > build.log 2>&1 || echo "failed: $?"
 LANG=C sort file
 alias ll=\(aqls \-l\(aq
 chsh \-s /usr/bin/gosh
 .fi
 .SH SEE ALSO
 .BR sh (1),
 .BR bash (1),
 .BR chsh (1),
 .BR shells (5)
 .SH AUTHOR
 Florian Walther <florian.walther@certainity.com>
@@ -0,0 +1,841 @@
 package main
 // Parser and executor for command lines and scripts: lists (; & && || and
 // newlines), pipelines, ! and the control structures if, for, while and
 // until. Simple commands (with their pipes and redirections) are kept as
 // text; they are expanded and run by execCommand only when they are
 // executed, so that e.g. the variable of a for loop is expanded anew in
 // every iteration.
 import (
 	"errors"
 	"fmt"
 	"os"
 	"strconv"
 	"strings"
 	"syscall"
 )
 // incompleteError is returned by parse if the input ends inside a
 // construct (if without fi, an open quote, a trailing && ...): an
 // interactive shell then reads another line.
 type incompleteError struct{}
 func (incompleteError) Error() string { return "syntax error: unexpected end of input" }
 var errIncomplete error = incompleteError{}
 // loopControl is returned by break and continue and ends the given number of
 // enclosing loops (break) or iterations (continue).
 type loopControl struct {
 	isBreak bool
 	n       int
 }
 func (c loopControl) Error() string {
 	if c.isBreak {
 		return "break"
 	}
 	return "continue"
 }
 // loopDepth is the number of loops that are currently running.
 var loopDepth int
 // aliasExpansion is false while the result of an alias expansion runs, so
 // that it is not expanded again.
 var aliasExpansion = true
 // reserved words that end a list; they are only recognized as the first word
 // of a command.
 var terminators = map[string]bool{"then": true, "elif": true, "else": true, "fi": true, "do": true, "done": true}
 // ---------------------------------------------------------------------------
 // Lexer
 type tokenKind int
 const (
 	tWord tokenKind = iota
 	tOp             // ; & && || | or newline
 )
 type rawToken struct {
 	kind       tokenKind
 	text       string
 	start, end int
 }
 // joinContinuationLines removes backslash-newline (outside single quotes),
 // which continues a line. continued reports whether src ends with such a
 // continuation (so that the command goes on in the next line).
 func joinContinuationLines(src string) (joined string, continued bool) {
 	if !strings.Contains(src, "\\\n") {
 		return src, false
 	}
 	var b strings.Builder
 	var quote byte
 	for i := 0; i < len(src); i++ {
 		ch := src[i]
 		switch {
 		case quote == '\'':
 			if ch == '\'' {
 				quote = 0
 			}
 		case ch == '\\' && i+1 < len(src):
 			if src[i+1] == '\n' {
 				i++
 				continued = i == len(src)-1
 				continue
 			}
 			continued = false
 			b.WriteByte(ch)
 			i++
 			ch = src[i]
 		case ch == '"':
 			if quote == '"' {
 				quote = 0
 			} else {
 				quote = '"'
 			}
 		case ch == '\'' && quote == 0:
 			quote = '\''
 		}
 		if ch != '\n' && ch != ' ' && ch != '\t' {
 			continued = false
 		}
 		b.WriteByte(ch)
 	}
 	return b.String(), continued
 }
 // lex splits src into words and list operators. Words keep their quotes,
 // escapes, $(...) and redirections; they are only split at blanks and list
 // operators.
 func lex(src string) ([]rawToken, error) {
 	var toks []rawToken
 	op := func(text string, i int) {
 		toks = append(toks, rawToken{tOp, text, i, i + len(text)})
 	}
 	for i := 0; i < len(src); {
 		ch := src[i]
 		next := byte(0)
 		if i+1 < len(src) {
 			next = src[i+1]
 		}
 		switch {
 		case ch == ' ' || ch == '\t':
 			i++
 		case ch == '\n' || ch == ';':
 			op(string(ch), i)
 			i++
 		case ch == '#':
 			// Comment until the end of the line
 			for i < len(src) && src[i] != '\n' {
 				i++
 			}
 		case ch == '|' && next == '|', ch == '&' && next == '&':
 			op(src[i:i+2], i)
 			i += 2
 		case ch == '|', ch == '&' && next != '>':
 			op(string(ch), i)
 			i++
 		default:
 			end, err := lexWord(src, i)
 			if err != nil {
 				return nil, err
 			}
 			toks = append(toks, rawToken{tWord, src[i:end], i, end})
 			i = end
 		}
 	}
 	return toks, nil
 }
 // lexWord returns the end of the word that starts at src[i].
 func lexWord(src string, i int) (int, error) {
 	var quote byte
 	for j := i; j < len(src); j++ {
 		ch := src[j]
 		switch {
 		case quote == '\'':
 			if ch == '\'' {
 				quote = 0
 			}
 		case ch == '\\':
 			if j+1 == len(src) {
 				return 0, errIncomplete
 			}
 			j++
 		case isSubstStart(src, j):
 			end := substEnd(src, j)
 			if end < 0 {
 				return 0, errIncomplete
 			}
 			j = end
 		case ch == '$' && j+1 < len(src) && src[j+1] == '{':
 			if k := strings.IndexByte(src[j:], '}'); k >= 0 {
 				j += k
 			}
 		case quote == '"':
 			if ch == '"' {
 				quote = 0
 			}
 		case ch == '"' || ch == '\'':
 			quote = ch
 		case ch == ' ' || ch == '\t' || ch == '\n' || ch == ';' || ch == '|':
 			return j, nil
 		case ch == '&':
 			// &>, >& and <& are redirections, not the & operator
 			if !(j+1 < len(src) && src[j+1] == '>') && !(j > i && (src[j-1] == '>' || src[j-1] == '<')) {
 				return j, nil
 			}
 		}
 	}
 	if quote != 0 {
 		return 0, errIncomplete
 	}
 	return len(src), nil
 }
 // ---------------------------------------------------------------------------
 // Syntax tree
 // node is a command that can be executed: it returns the error of the last
 // command it ran (so that exitStatus gives its status).
 type node interface {
 	exec() error
 }
 // listNode is a list of and-or lists separated by ;, & or newlines.
 type listNode struct {
 	items []listEntry
 }
 type listEntry struct {
 	andOr      *andOrNode
 	background bool
 }
 // andOrNode is a pipeline followed by && and || pipelines.
 type andOrNode struct {
 	first *pipelineNode
 	rest  []andOrPart
 }
 type andOrPart struct {
 	op       string // && or ||
 	pipeline *pipelineNode
 }
 // pipelineNode is a simple command (whose text may contain a pipeline) or a
 // control structure, optionally negated with !.
 type pipelineNode struct {
 	negate bool
 	cmd    node
 }
 // simpleNode is the text of a pipeline of simple commands.
 type simpleNode struct {
 	text string
 }
 type ifNode struct {
 	conds    []*listNode
 	bodies   []*listNode
 	elseBody *listNode
 }
 type forNode struct {
 	name  string
 	words string // the words after "in", expanded when the loop starts
 	hasIn bool
 	body  *listNode
 }
 type whileNode struct {
 	until bool
 	cond  *listNode
 	body  *listNode
 }
 // singleSimple returns the simple command if the list is just that.
 func (l *listNode) singleSimple() *simpleNode {
 	if len(l.items) != 1 || l.items[0].background {
 		return nil
 	}
 	ao := l.items[0].andOr
 	if len(ao.rest) > 0 || ao.first.negate {
 		return nil
 	}
 	s, _ := ao.first.cmd.(*simpleNode)
 	return s
 }
 // ---------------------------------------------------------------------------
 // Parser
 type parser struct {
 	src  string
 	toks []rawToken
 	pos  int
 }
 // parse parses a command line or script. It returns errIncomplete if the
 // input ends inside a construct.
 func parse(src string) (*listNode, error) {
 	src, continued := joinContinuationLines(src)
 	if continued {
 		return nil, errIncomplete
 	}
 	toks, err := lex(src)
 	if err != nil {
 		return nil, err
 	}
 	p := &parser{src: src, toks: toks}
 	list, err := p.parseList(nil)
 	if err != nil {
 		return nil, err
 	}
 	if t := p.peek(); t != nil {
 		return nil, p.unexpected(t)
 	}
 	return list, nil
 }
 func (p *parser) peek() *rawToken {
 	if p.pos < len(p.toks) {
 		return &p.toks[p.pos]
 	}
 	return nil
 }
 func (p *parser) peekWord(words ...string) bool {
 	t := p.peek()
 	if t == nil || t.kind != tWord {
 		return false
 	}
 	for _, w := range words {
 		if t.text == w {
 			return true
 		}
 	}
 	return false
 }
 func (p *parser) skipNewlines() {
 	for t := p.peek(); t != nil && t.kind == tOp && t.text == "\n"; t = p.peek() {
 		p.pos++
 	}
 }
 func (p *parser) unexpected(t *rawToken) error {
 	if t.text == "\n" {
 		return syntaxError("newline")
 	}
 	return syntaxError(t.text)
 }
 // expect consumes the reserved word w.
 func (p *parser) expect(w string) error {
 	t := p.peek()
 	if t == nil {
 		return errIncomplete
 	}
 	if t.kind != tWord || t.text != w {
 		return p.unexpected(t)
 	}
 	p.pos++
 	return nil
 }
 // parseList parses and-or lists until the end of the input or one of the
 // reserved words in terms at the start of a command.
 func (p *parser) parseList(terms map[string]bool) (*listNode, error) {
 	list := &listNode{}
 	for {
 		p.skipNewlines()
 		t := p.peek()
 		if t == nil || t.kind == tWord && terms[t.text] {
 			return list, nil
 		}
 		ao, err := p.parseAndOr()
 		if err != nil {
 			return nil, err
 		}
 		entry := listEntry{andOr: ao}
 		t = p.peek()
 		switch {
 		case t == nil:
 		case t.kind == tOp && (t.text == ";" || t.text == "&" || t.text == "\n"):
 			p.pos++
 			entry.background = t.text == "&"
 		case t.kind == tWord && terms[t.text]:
 			// e.g. "fi" right after the end of a nested control structure
 		default:
 			return nil, p.unexpected(t)
 		}
 		if entry.background {
 			if _, ok := ao.first.cmd.(*simpleNode); !ok || len(ao.rest) > 0 || ao.first.negate {
 				return nil, errors.New("only simple commands and pipelines can run in the background")
 			}
 		}
 		list.items = append(list.items, entry)
 	}
 }
 // nonEmpty returns an error if a list that must contain commands is empty.
 func (p *parser) nonEmpty(list *listNode) error {
 	if len(list.items) > 0 {
 		return nil
 	}
 	if t := p.peek(); t != nil {
 		return p.unexpected(t)
 	}
 	return errIncomplete
 }
 func (p *parser) parseAndOr() (*andOrNode, error) {
 	first, err := p.parsePipeline()
 	if err != nil {
 		return nil, err
 	}
 	ao := &andOrNode{first: first}
 	for {
 		t := p.peek()
 		if t == nil || t.kind != tOp || (t.text != "&&" && t.text != "||") {
 			return ao, nil
 		}
 		p.pos++
 		p.skipNewlines()
 		if p.peek() == nil {
 			return nil, errIncomplete
 		}
 		next, err := p.parsePipeline()
 		if err != nil {
 			return nil, err
 		}
 		ao.rest = append(ao.rest, andOrPart{op: t.text, pipeline: next})
 	}
 }
 func (p *parser) parsePipeline() (*pipelineNode, error) {
 	pl := &pipelineNode{}
 	if p.peekWord("!") {
 		pl.negate = true
 		p.pos++
 	}
 	t := p.peek()
 	if t == nil {
 		return nil, errIncomplete
 	}
 	if t.kind == tOp || terminators[t.text] {
 		return nil, p.unexpected(t)
 	}
 	var err error
 	compound := true
 	switch t.text {
 	case "if":
 		pl.cmd, err = p.parseIf()
 	case "for":
 		pl.cmd, err = p.parseFor()
 	case "while", "until":
 		pl.cmd, err = p.parseWhile()
 	default:
 		compound = false
 		pl.cmd, err = p.parseSimple()
 	}
 	if err != nil {
 		return nil, err
 	}
 	if compound {
 		if t := p.peek(); t != nil {
 			switch {
 			case t.kind == tOp && t.text == "|":
 				return nil, errors.New("control structures in pipelines are not supported")
 			case t.kind == tWord && !terminators[t.text]:
 				return nil, fmt.Errorf("redirections of control structures are not supported (near `%s')", t.text)
 			}
 		}
 	}
 	return pl, nil
 }
 // parseSimple parses a pipeline of simple commands and returns its text.
 func (p *parser) parseSimple() (*simpleNode, error) {
 	start := p.toks[p.pos].start
 	end := start
 	for t := p.peek(); t != nil; t = p.peek() {
 		if t.kind == tWord {
 			end = t.end
 			p.pos++
 			continue
 		}
 		if t.text != "|" {
 			break
 		}
 		p.pos++
 		end = t.end
 		p.skipNewlines()
 		next := p.peek()
 		switch {
 		case next == nil:
 			return nil, errIncomplete
 		case next.kind == tOp || terminators[next.text]:
 			return nil, p.unexpected(next)
 		case next.text == "if" || next.text == "for" || next.text == "while" || next.text == "until":
 			return nil, errors.New("control structures in pipelines are not supported")
 		}
 	}
 	return &simpleNode{text: p.src[start:end]}, nil
 }
 func (p *parser) parseIf() (*ifNode, error) {
 	p.pos++ // if
 	n := &ifNode{}
 	for {
 		cond, err := p.parseList(map[string]bool{"then": true})
 		if err == nil {
 			err = p.nonEmpty(cond)
 		}
 		if err == nil {
 			err = p.expect("then")
 		}
 		if err != nil {
 			return nil, err
 		}
 		body, err := p.parseList(map[string]bool{"elif": true, "else": true, "fi": true})
 		if err == nil {
 			err = p.nonEmpty(body)
 		}
 		if err != nil {
 			return nil, err
 		}
 		n.conds = append(n.conds, cond)
 		n.bodies = append(n.bodies, body)
 		t := p.peek()
 		if t == nil {
 			return nil, errIncomplete
 		}
 		p.pos++
 		switch t.text {
 		case "elif":
 			continue
 		case "else":
 			body, err := p.parseList(map[string]bool{"fi": true})
 			if err == nil {
 				err = p.nonEmpty(body)
 			}
 			if err == nil {
 				err = p.expect("fi")
 			}
 			if err != nil {
 				return nil, err
 			}
 			n.elseBody = body
 		}
 		return n, nil // fi
 	}
 }
 func (p *parser) parseFor() (*forNode, error) {
 	p.pos++ // for
 	t := p.peek()
 	if t == nil {
 		return nil, errIncomplete
 	}
 	if t.kind != tWord || !isVarName(t.text) {
 		return nil, fmt.Errorf("for: `%s': not a valid identifier", sanitize(t.text))
 	}
 	n := &forNode{name: t.text}
 	p.pos++
 	p.skipNewlines()
 	if p.peekWord("in") {
 		p.pos++
 		n.hasIn = true
 		var words []string
 		for t := p.peek(); t != nil && t.kind == tWord; t = p.peek() {
 			words = append(words, t.text)
 			p.pos++
 		}
 		n.words = strings.Join(words, " ")
 	}
 	t = p.peek()
 	switch {
 	case t == nil:
 		return nil, errIncomplete
 	case t.kind == tOp && (t.text == ";" || t.text == "\n"):
 		p.pos++
 	case !n.hasIn && t.kind == tWord && t.text == "do":
 	default:
 		return nil, p.unexpected(t)
 	}
 	p.skipNewlines()
 	body, err := p.parseLoopBody()
 	if err != nil {
 		return nil, err
 	}
 	n.body = body
 	return n, nil
 }
 func (p *parser) parseWhile() (*whileNode, error) {
 	n := &whileNode{until: p.peek().text == "until"}
 	p.pos++
 	cond, err := p.parseList(map[string]bool{"do": true})
 	if err == nil {
 		err = p.nonEmpty(cond)
 	}
 	if err != nil {
 		return nil, err
 	}
 	n.cond = cond
 	body, err := p.parseLoopBody()
 	if err != nil {
 		return nil, err
 	}
 	n.body = body
 	return n, nil
 }
 // parseLoopBody parses "do list done".
 func (p *parser) parseLoopBody() (*listNode, error) {
 	if err := p.expect("do"); err != nil {
 		return nil, err
 	}
 	body, err := p.parseList(map[string]bool{"done": true})
 	if err == nil {
 		err = p.nonEmpty(body)
 	}
 	if err == nil {
 		err = p.expect("done")
 	}
 	return body, err
 }
 // ---------------------------------------------------------------------------
 // Execution
 // isAbort reports whether err stops the execution of the enclosing lists:
 // break, continue, or a command that was interrupted with Ctrl+C (like in
 // bash, Ctrl+C aborts the whole command line, e.g. a loop).
 func isAbort(err error) bool {
 	var lc loopControl
 	return errors.As(err, &lc) || exitStatus(err) == 128+int(syscall.SIGINT)
 }
 // silent returns an error with only the exit status of err, for errors that
 // were already reported.
 func silent(err error) error {
 	if err == nil {
 		return nil
 	}
 	return statusError(exitStatus(err))
 }
 func (l *listNode) exec() error {
 	var err error
 	for _, entry := range l.items {
 		printError(err)
 		if entry.background {
 			err = entry.andOr.first.cmd.(*simpleNode).run(true)
 		} else {
 			err = entry.andOr.exec()
 		}
 		lastStatus = exitStatus(err)
 		if isAbort(err) {
 			return err
 		}
 	}
 	return err
 }
 func (a *andOrNode) exec() error {
 	err := a.first.exec()
 	for _, part := range a.rest {
 		lastStatus = exitStatus(err)
 		if isAbort(err) {
 			return err
 		}
 		if (part.op == "&&") != (lastStatus == 0) {
 			continue
 		}
 		printError(err)
 		err = part.pipeline.exec()
 	}
 	return err
 }
 func (pl *pipelineNode) exec() error {
 	err := pl.cmd.exec()
 	if !pl.negate || isAbort(err) {
 		return err
 	}
 	printError(err)
 	if exitStatus(err) == 0 {
 		return statusError(1)
 	}
 	return nil
 }
 func (s *simpleNode) exec() error {
 	return s.run(false)
 }
 // run executes the simple command, in the background if background is set.
 // Aliases are expanded here (in interactive shells), so that they work at
 // the start of every command, also inside control structures.
 func (s *simpleNode) run(background bool) error {
 	text := s.text
 	if interactiveShell && aliasExpansion {
 		if expanded := expandAliases(text); expanded != text {
 			tree, err := parse(expanded)
 			if err != nil {
 				return err
 			}
 			if simple := tree.singleSimple(); simple != nil {
 				text = simple.text
 			} else {
 				if background {
 					return errors.New("an alias with a command list cannot run in the background")
 				}
 				aliasExpansion = false
 				defer func() { aliasExpansion = true }()
 				return tree.exec()
 			}
 		}
 	}
 	return execCommand(text, background)
 }
 func (n *ifNode) exec() error {
 	for i, cond := range n.conds {
 		err := cond.exec()
 		if isAbort(err) {
 			return err
 		}
 		printError(err)
 		if exitStatus(err) == 0 {
 			return n.bodies[i].exec()
 		}
 	}
 	if n.elseBody != nil {
 		return n.elseBody.exec()
 	}
 	lastStatus = 0
 	return nil
 }
 // runLoopBody runs one iteration of a loop. It returns whether the loop
 // must stop, and the error to return from the loop.
 func runLoopBody(body *listNode, result *error) (stop bool, err error) {
 	err = body.exec()
 	var lc loopControl
 	if errors.As(err, &lc) {
 		*result = nil
 		if lc.n > 1 {
 			lc.n--
 			return true, lc // ends an outer loop too
 		}
 		return lc.isBreak, nil
 	}
 	if isAbort(err) {
 		return true, err
 	}
 	printError(err)
 	*result = silent(err)
 	return false, nil
 }
 func (n *whileNode) exec() error {
 	loopDepth++
 	defer func() { loopDepth-- }()
 	var result error
 	for {
 		err := n.cond.exec()
 		if isAbort(err) {
 			return err
 		}
 		printError(err)
 		if (exitStatus(err) == 0) == n.until {
 			break
 		}
 		if stop, err := runLoopBody(n.body, &result); stop {
 			if err != nil {
 				return err
 			}
 			break
 		}
 	}
 	lastStatus = exitStatus(result)
 	return result
 }
 func (n *forNode) exec() error {
 	var words []string
 	if n.hasIn {
 		var err error
 		if words, err = expandWordList(n.words); err != nil {
 			return err
 		}
 	}
 	loopDepth++
 	defer func() { loopDepth-- }()
 	var result error
 	for _, word := range words {
 		os.Setenv(n.name, word)
 		if stop, err := runLoopBody(n.body, &result); stop {
 			if err != nil {
 				return err
 			}
 			break
 		}
 	}
 	lastStatus = exitStatus(result)
 	return result
 }
 // expandWordList expands the words of a for loop like the arguments of a
 // command (braces, ~, variables, $(...), wildcards).
 func expandWordList(text string) ([]string, error) {
 	text, err := expandBraceWords(text)
 	if err != nil {
 		return nil, err
 	}
 	tokens, err := tokenize(text)
 	if err != nil {
 		return nil, fmt.Errorf("invalid input: %w", err)
 	}
 	var words []string
 	for _, t := range tokens {
 		if t.op != "" {
 			return nil, syntaxError(t.op)
 		}
 		words = append(words, expandWord(t)...)
 	}
 	return words, nil
 }
 // builtinLoopControl implements break [n] and continue [n].
 func builtinLoopControl(args []string) error {
 	n := 1
 	if len(args) > 1 {
 		var err error
 		if n, err = strconv.Atoi(args[1]); err != nil || n < 1 {
 			return fmt.Errorf("%s: %s: loop count out of range", args[0], sanitize(args[1]))
 		}
 	}
 	if loopDepth == 0 {
 		return fmt.Errorf("%s: only meaningful in a loop", args[0])
 	}
 	return loopControl{isBreak: args[0] == "break", n: min(n, loopDepth)}
 }
@@ -0,0 +1,164 @@
 package main
 import (
 	"os"
 	"strings"
 	"testing"
 )
 // runIn runs input in a temporary directory and returns the content of the
 // file "out" there.
 func runIn(t *testing.T, input string) string {
 	t.Helper()
 	origDir, _ := os.Getwd()
 	defer os.Chdir(origDir)
 	os.Chdir(t.TempDir())
 	execInput(input)
 	data, _ := os.ReadFile("out")
 	return string(data)
 }
 func TestExec_If(t *testing.T) {
 	tests := []struct {
 		input string
 		want  string
 	}{
 		{"if true; then echo yes >> out; fi", "yes\n"},
 		{"if false; then echo yes >> out; fi", ""},
 		{"if false; then echo a >> out; else echo b >> out; fi", "b\n"},
 		{"if false; then echo a >> out; elif true; then echo b >> out; else echo c >> out; fi", "b\n"},
 		{"if false; then echo a >> out; elif false; then echo b >> out; else echo c >> out; fi", "c\n"},
 		{"if ! false; then echo negated >> out; fi", "negated\n"},
 		{"if true && false; then echo a >> out; else echo b >> out; fi", "b\n"},
 		{"if false || true; then echo a >> out; fi", "a\n"},
 		{"if echo cond >> out; then echo body >> out; fi", "cond\nbody\n"},
 		{"if true\nthen\n  echo multi >> out\n  echo line >> out\nfi", "multi\nline\n"},
 		{"if true; then if false; then echo a >> out; else echo nested >> out; fi; fi", "nested\n"},
 		{"if [ -d / ]; then echo dir >> out; fi", "dir\n"},
 	}
 	for _, tc := range tests {
 		if got := runIn(t, tc.input); got != tc.want {
 			t.Errorf("%q: out = %q, want %q", tc.input, got, tc.want)
 		}
 	}
 }
 func TestExec_Loops(t *testing.T) {
 	defer os.Unsetenv("GOSH_I")
 	tests := []struct {
 		input string
 		want  string
 	}{
 		{"for x in a b c; do echo $x >> out; done", "a\nb\nc\n"},
 		{"for x in {1..3}; do echo $x >> out; done", "1\n2\n3\n"},
 		{"for x in $(echo a b); do echo $x >> out; done", "a\nb\n"},
 		{"for x in \"a b\" c; do echo $x >> out; done", "a b\nc\n"},
 		{"touch f1 f2; for f in f*; do echo $f >> out; done", "f1\nf2\n"},
 		{"for x in; do echo never >> out; done", ""},
 		{"for x; do echo never >> out; done", ""},
 		{"set GOSH_I=0; while [ $GOSH_I -lt 3 ]; do echo $GOSH_I >> out; set GOSH_I=$(expr $GOSH_I + 1); done", "0\n1\n2\n"},
 		{"set GOSH_I=3; until [ $GOSH_I -eq 0 ]; do echo $GOSH_I >> out; set GOSH_I=$(expr $GOSH_I - 1); done", "3\n2\n1\n"},
 		{"while false; do echo never >> out; done", ""},
 		// The loop variable keeps the last value
 		{"for GOSH_I in a b; do :; done; echo $GOSH_I > out", "b\n"},
 		// break and continue
 		{"for x in 1 2 3 4; do if [ $x = 3 ]; then break; fi; echo $x >> out; done", "1\n2\n"},
 		{"for x in 1 2 3; do if [ $x = 2 ]; then continue; fi; echo $x >> out; done", "1\n3\n"},
 		{"for a in 1 2; do for b in x y; do if [ $b = y ]; then continue 2; fi; echo $a$b >> out; done; done", "1x\n2x\n"},
 		{"for a in 1 2; do for b in x y; do echo $a$b >> out; break 2; done; done", "1x\n"},
 		{"for a in 1 2; do for b in x y; do echo $a$b >> out; break 5; done; done", "1x\n"},
 		{"while true; do echo once >> out; break; done", "once\n"},
 		{"for x in 1 2; do echo $x >> out; break; echo never >> out; done; echo after >> out", "1\nafter\n"},
 	}
 	for _, tc := range tests {
 		if got := runIn(t, tc.input); got != tc.want {
 			t.Errorf("%q: out = %q, want %q", tc.input, got, tc.want)
 		}
 	}
 	if loopDepth != 0 {
 		t.Errorf("loopDepth = %d after the loops", loopDepth)
 	}
 }
 func TestExec_Status(t *testing.T) {
 	tests := []struct {
 		input  string
 		status int
 	}{
 		{"if false; then :; fi", 0},
 		{"if true; then false; fi", 1},
 		{"if false; then :; else sh -c 'exit 3'; fi", 3},
 		{"for x in a; do false; done", 1},
 		{"for x in a; do false; done; true", 0},
 		{"for x in; do false; done", 0},
 		{"while false; do :; done", 0},
 		{"for x in a b; do sh -c 'exit 4'; break; done", 0},
 		{"! true", 1},
 		{"! false", 0},
 		{"! gosh-no-such-command", 0},
 		{":", 0},
 		{"break", 1},
 		{"continue", 1},
 		{"for x in a; do break x; done", 1},
 		{"if a; then", 2},
 		{"fi", 2},
 	}
 	for _, tc := range tests {
 		runIn(t, tc.input)
 		if lastStatus != tc.status {
 			t.Errorf("%q: $? = %d, want %d", tc.input, lastStatus, tc.status)
 		}
 	}
 	if err := execInput("break"); err == nil || err.Error() != "break: only meaningful in a loop" {
 		t.Errorf("break outside a loop: %v", err)
 	}
 }
 func TestRunScript_MultiLine(t *testing.T) {
 	origDir, _ := os.Getwd()
 	defer os.Chdir(origDir)
 	os.Chdir(t.TempDir())
 	script := `# a script with control structures
 for x in a b
 do
  if [ $x = a ]; then
    echo first >> out
  else
    echo second >> out
  fi
 done
 echo continued \
  line >> out
 `
 	if status := runScript(strings.NewReader(script), ""); status != 0 {
 		t.Errorf("status = %d", status)
 	}
 	if got, _ := os.ReadFile("out"); string(got) != "first\nsecond\ncontinued line\n" {
 		t.Errorf("out = %q", got)
 	}
 	// A script that ends inside a control structure is a syntax error
 	if status := runScript(strings.NewReader("echo ok >> out2\nif true; then\n  echo never >> out2\n"), ""); status != 2 {
 		t.Errorf("status = %d for an unterminated if, want 2", status)
 	}
 	if got, _ := os.ReadFile("out2"); string(got) != "ok\n" {
 		t.Errorf("out2 = %q", got)
 	}
 }
 func TestExec_AliasesInControlStructures(t *testing.T) {
 	withAliases(t, map[string]string{"say": "echo said", "both": "echo one >> out; echo two"})
 	defer func(saved bool) { interactiveShell = saved }(interactiveShell)
 	interactiveShell = true
 	if got := runIn(t, "for x in a b; do say $x >> out; done"); got != "said a\nsaid b\n" {
 		t.Errorf("alias in for: out = %q", got)
 	}
 	if got := runIn(t, "if true; then both >> out; fi"); got != "one\ntwo\n" {
 		t.Errorf("alias with a list in if: out = %q", got)
 	}
 	if got := runIn(t, "if say x > out; then :; fi"); got != "said x\n" {
 		t.Errorf("alias in condition: out = %q", got)
 	}
 }
@@ -0,0 +1,98 @@
 package main
 // Command substitution: $(command) is replaced by the output of command,
 // which runs in a subshell (a new gosh process), so that cd, set etc. in it
 // do not change the shell.
 import (
 	"bytes"
 	"errors"
 	"os"
 	"os/exec"
 	"strings"
 	"syscall"
 )
 // subshellPath is the gosh binary used for command substitution; empty means
 // the running executable. Tests set it, since there the running executable is
 // the test binary.
 var subshellPath string
 // substStatus is the exit status of the last command substitution of the
 // current command (a command that consists only of a substitution has this
 // status, like in sh).
 var substStatus int
 // isSubstStart reports whether a command substitution $( starts at s[i].
 func isSubstStart(s string, i int) bool {
 	return s[i] == '$' && i+1 < len(s) && s[i+1] == '('
 }
 // substEnd returns the index of the ) that ends the command substitution
 // starting with $( at s[i], or -1 if it is not terminated. Quotes, escapes
 // and nested substitutions inside are taken into account.
 func substEnd(s string, i int) int {
 	depth := 0
 	var quote byte
 	for j := i + 1; j < len(s); j++ {
 		ch := s[j]
 		switch {
 		case quote == '\'':
 			if ch == '\'' {
 				quote = 0
 			}
 		case ch == '\\':
 			j++
 		case quote == '"':
 			if ch == '"' {
 				quote = 0
 			} else if isSubstStart(s, j) {
 				end := substEnd(s, j)
 				if end < 0 {
 					return -1
 				}
 				j = end
 			}
 		case ch == '"' || ch == '\'':
 			quote = ch
 		case ch == '(':
 			depth++
 		case ch == ')':
 			depth--
 			if depth == 0 {
 				return j
 			}
 		}
 	}
 	return -1
 }
 // commandSubst runs command in a subshell and returns its output without
 // trailing newlines. stdin and stderr are those of the shell.
 func commandSubst(command string) (string, error) {
 	if strings.HasPrefix(command, "(") {
 		return "", errors.New("arithmetic expansion $((...)) is not supported")
 	}
 	path := subshellPath
 	if path == "" {
 		var err error
 		if path, err = os.Executable(); err != nil {
 			return "", err
 		}
 	}
 	var out bytes.Buffer
 	cmd := exec.Command(path, "-c", command)
 	cmd.Stdin, cmd.Stdout, cmd.Stderr = os.Stdin, &out, os.Stderr
 	err := cmd.Run()
 	substStatus = exitStatus(err)
 	if substStatus == 128+int(syscall.SIGINT) {
 		// Ctrl+C aborts the whole command, like in bash
 		return "", statusError(substStatus)
 	}
 	var exitErr *exec.ExitError
 	if err != nil && !errors.As(err, &exitErr) {
 		return "", err
 	}
 	return strings.TrimRight(out.String(), "\n"), nil
 }
@@ -0,0 +1,104 @@
 package main
 import (
 	"os"
 	"testing"
 )
 func TestSubstEnd(t *testing.T) {
 	tests := []struct {
 		s    string
 		want int
 	}{
 		{"$(echo a)", 8},
 		{"$(echo a) b", 8},
 		{"$(echo $(date))x", 14},
 		{`$(echo ")")`, 10},
 		{`$(echo ')')`, 10},
 		{`$(echo \))`, 9},
 		{`$(echo "$(echo ")")")`, 20},
 		{"$(echo (a))", 10},
 		{"$(echo a", -1},
 		{`$(echo ")`, -1},
 	}
 	for _, tc := range tests {
 		if got := substEnd(tc.s, 0); got != tc.want {
 			t.Errorf("substEnd(%q) = %d, want %d", tc.s, got, tc.want)
 		}
 	}
 }
 func TestExpandAliasesAndBraces_SkipSubstitution(t *testing.T) {
 	withAliases(t, map[string]string{"ll": "ls -l"})
 	if got := expandAliases("echo $(ll; ll) && ll"); got != "echo $(ll; ll) && ls -l" {
 		t.Errorf("expandAliases = %q", got)
 	}
 	got, err := expandBraceWords("echo $(echo {a,b}) {c,d}")
 	if err != nil || got != "echo $(echo {a,b}) c d" {
 		t.Errorf("expandBraceWords = %q, %v", got, err)
 	}
 }
 func TestExecInput_CommandSubstitution(t *testing.T) {
 	origDir, _ := os.Getwd()
 	defer os.Chdir(origDir)
 	dir := t.TempDir()
 	os.Chdir(dir)
 	os.WriteFile("a.go", nil, 0644)
 	os.WriteFile("b.go", nil, 0644)
 	tests := []struct {
 		input string
 		want  string
 	}{
 		{"echo $(echo hello) > out", "hello\n"},
 		// Unquoted, the output is split into words
 		{"printf '[%s]' $(printf 'a b\\nc\\n\\n') > out", "[a][b][c]"},
 		{"printf '[%s]' x$(echo a b)y > out", "[xa][by]"},
 		// Quoted, it is a single word, only trailing newlines are removed
 		{`printf '[%s]' "$(printf 'a  b\nc\n\n')" > out`, "[a  b\nc]"},
 		{`printf '[%s]' "$(true)" > out`, "[]"},
 		{"printf '[%s]' $(true) x > out", "[x]"},
 		// Nested, with quotes and operators inside
 		{"echo $(echo $(echo nested)) > out", "nested\n"},
 		{`echo "$(echo "a;b|c")" > out`, "a;b|c\n"},
 		{"echo $(echo a | tr a-z A-Z) > out", "A\n"},
 		// Wildcards in the output are not expanded, in the command they are
 		{`echo $(echo "*") > out`, "*\n"},
 		{"echo $(echo *.go) > out", "a.go b.go\n"},
 		// Quoted or escaped, $( is literal
 		{`echo '$(echo a)' \$(echo b) > out`, "$(echo a) $(echo b)\n"},
 		// The subshell does not change the shell
 		{"echo $(cd /; pwd) > out; pwd >> out", "/\n" + dir + "\n"},
 		{"set GOSH_SUBST=$(echo value); echo $GOSH_SUBST > out", "value\n"},
 	}
 	for _, tc := range tests {
 		if err := execInput(tc.input); err != nil {
 			t.Errorf("%q: %v", tc.input, err)
 		}
 		if got, _ := os.ReadFile("out"); string(got) != tc.want {
 			t.Errorf("%q: out = %q, want %q", tc.input, got, tc.want)
 		}
 	}
 	os.Unsetenv("GOSH_SUBST")
 	// A command that consists only of a substitution has its status
 	execInput("$(sh -c 'exit 3')")
 	if lastStatus != 3 {
 		t.Errorf("$? = %d after $(exit 3), want 3", lastStatus)
 	}
 	// Otherwise the status of the command counts
 	execInput("echo $(false) > out")
 	if lastStatus != 0 {
 		t.Errorf("$? = %d after echo $(false), want 0", lastStatus)
 	}
 	for input, wantErr := range map[string]string{
 		"echo $(echo a":   "syntax error: unexpected end of input",
 		"echo $((1 + 2))": "invalid input: arithmetic expansion $((...)) is not supported",
 	} {
 		if err := execInput(input); err == nil || err.Error() != wantErr {
 			t.Errorf("%q: error %v, want %q", input, err, wantErr)
 		}
 	}
 }
Author	SHA1	Message	Date
Florian WaltherandClaude Opus 5.5	9fe8b06fba	add man page gosh(1) and include it in the deb/rpm packages Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>	2026-10-04 13:59:09 +02:00
Florian WaltherandClaude Opus 5.5	22ce8c00d4	add assignments name=value and unset - name=value (one or more) without a command sets variables of the shell - name=value before a command sets them only in its environment (for builtins only while they run) - an assignment needs an unquoted name and =; the value is not split and not expanded as wildcard or brace pattern, ~ is expanded after = and : - the status of an assignment is the one of its last $(...) - new builtin unset Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>	2026-10-04 00:17:38 +02:00
Florian Walther	fb94e98da5	updated README	2026-10-04 00:16:29 +02:00
Florian WaltherandClaude Opus 5.5	f79fb0b8d5	add control structures: if, for, while, until - new parser (parser.go) for lists, pipelines, ! and if/elif/else/fi, for ... in ... do/done, while/until ... do/done; simple commands are kept as text and expanded when they run (in every iteration) - break [n], continue [n] and the : builtin - incomplete input (open control structure, trailing &&, \|, quote or backslash) continues on the next line: prompt "> " in interactive shells, scripts and startup files read on - Ctrl+C aborts the whole command line, including loops - aliases are expanded at the start of every simple command, also inside control structures - control structures in pipelines, with redirections or in the background are reported as not supported - completion: commands after if, then, do etc. - main_test.go reformatted with gofmt Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>	2026-10-04 00:05:28 +02:00
Florian WaltherandClaude Opus 5.5	e49fe6fe11	add command substitution $(...) - $(command) is replaced by the output of command, which runs in a subshell (gosh -c), so cd/set in it do not change the shell - trailing newlines are removed; unquoted the output is split into words at blanks and newlines, "$(...)" stays one word; wildcards in the output are not expanded - nested substitutions, quotes and operators inside are handled; the list, alias and brace scanners skip $(...) as a whole - a command that consists only of a substitution has its exit status, Ctrl+C in a substitution aborts the command - $((...)) is reported as not supported Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>	2026-10-03 23:52:09 +02:00