show the exit status of a failed command in the prompt

- user@host:dir [N] $ after a command failed with exit status N,
  the plain prompt again after a successful command
- the status is colored bold red by default, configurable with the new
  GOSH_COLORS key error

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

README.md

@@ -30,13 +30,17 @@ Features:
     override with $GOSH_HISTFILE); lines starting with a space are not saved
   - Tab completion for commands and file paths
   - Tilde expansion (~, ~/path) at the start of unquoted words
+  - Brace expansion: a{b,c}d -> abd acd, {1..5}, {01..10..2}, {a..e}
   - Wildcards: * ? [abc] [a-z] [!abc] match file names (not hidden files
     unless the pattern starts with a dot); quoted wildcards and values of
     variables are not expanded, a pattern without match is kept as is
-  - Colored prompt (user@host green, red for root; directory blue),
+  - Prompt user@host:dir $, with [N] before the $ if the last command
-    configurable with $GOSH_COLORS, e.g. GOSH_COLORS='user=1;33:path=36'
+    failed with exit status N
-    (keys user, root, path; values are ANSI SGR codes, empty = no color);
+  - Colored prompt (user@host green, red for root; directory blue; exit
-    disabled with $NO_COLOR, TERM=dumb or when output is not a terminal
+    status red), configurable with $GOSH_COLORS, e.g.
+    GOSH_COLORS='user=1;33:path=36' (keys user, root, path, error; values
+    are ANSI SGR codes, empty = no color); disabled with $NO_COLOR,
+    TERM=dumb or when output is not a terminal
   - Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
     using an unset variable is an error, use ${VAR:-} for an empty default
   - Command lists: a ; b (run both), a && b (b only if a succeeded),
@@ -142,6 +146,35 @@ Status 127
 
 Schlägt ein Programm fehl, gibt gosh selbst keine Meldung mehr aus (das Programm meldet den Fehler selbst), nur bei Fehlern von gosh, z. B. wenn ein Befehl nicht gefunden wird.
 
+### Klammer-Expansion
+
+Wie in bash erzeugt `{…}` aus einem Wort mehrere Wörter:
+
+| Ausdruck          | ergibt                          |
+|-------------------|---------------------------------|
+| `a{b,c}d`         | `abd acd`                       |
+| `file{,.bak}`     | `file file.bak`                 |
+| `{a,b}{1,2}`      | `a1 a2 b1 b2`                   |
+| `x{a,{b,c}}`      | `xa xb xc` (verschachtelt)      |
+| `{1..5}`          | `1 2 3 4 5`                     |
+| `{5..1}`          | `5 4 3 2 1`                     |
+| `{1..10..3}`      | `1 4 7 10` (Schrittweite)       |
+| `{01..10..4}`     | `01 05 09` (mit führenden Nullen) |
+| `{a..e}`          | `a b c d e`                     |
+
+```
+$ mkdir -p projekt/{src,doc,test}
+$ cp config.yaml{,.bak}          # Sicherungskopie
+$ ls *.{go,md}
+$ touch log-{01..12}.txt
+```
+
+- Die Klammer-Expansion kommt zuerst, die Ergebnisse durchlaufen danach `~`, Variablen und Wildcards: `*.{go,md}` wird zu `*.go *.md`, `{${A},b}` zu `$A b`.
+- Ohne Komma (und ohne gültige Folge) bleiben Klammern stehen: `{a}`, `{}`, `{a..1}`. Auch `${VAR}` wird nicht angefasst.
+- In Anführungszeichen oder mit `\` davor sind die Zeichen normale Zeichen: `"{a,b}"`, `\{a,b\}`. Ein Komma lässt sich mit `\,` schützen: `{a\,b,c}` ergibt `a,b c`.
+- Bei einer Umleitung muss genau ein Wort herauskommen, `> {a,b}` meldet `ambiguous redirect`.
+- Ein Wort darf höchstens 100 000 Wörter erzeugen.
+
 ### Wildcards
 
 Wörter mit `*`, `?` oder `[...]` werden durch die passenden Dateinamen ersetzt, sortiert:
@@ -256,8 +289,25 @@ $ bg %2                       # oder: angehaltenen Job im Hintergrund weiterlauf
 - `exit` (oder Ctrl+D) mit angehaltenen Jobs warnt einmal (`there are stopped jobs`), ein zweites `exit` direkt danach beendet gosh.
 - `cd`, `set`, `export`, `exit`, `source`, `fg`, `bg` und `wait` lassen sich nicht mit `&` im Hintergrund starten.
 - In Skripten und mit `gosh -c` gibt es keine Job-Control (kein Ctrl+Z, kein `fg`/`bg`), `&` und `wait` funktionieren aber. Hintergrund-Jobs lesen dort von `/dev/null`.
+- Wird ein angehaltener Job von außen fortgesetzt (`kill -CONT`), zeigt `jobs` ihn weiter als `Stopped`, bis er endet oder erneut angehalten wird; `fg` und `bg` funktionieren trotzdem.
 - Einen Job beenden lässt sich mit `kill` über die Prozess-ID (z. B. `kill 12345`); `kill %1` versteht gosh noch nicht.
 
+### Prompt
+
+Der Prompt zeigt Benutzer, Rechner und Verzeichnis. Ist der letzte Befehl fehlgeschlagen, steht sein Exit-Status in eckigen Klammern davor, bis wieder ein Befehl erfolgreich war:
+
+```
+flow@host:~/src $ false
+flow@host:~/src [1] $ gibtsnicht
+gosh: gibtsnicht: command not found
+flow@host:~/src [127] $ sleep 100     # mit Ctrl+C abgebrochen
+^C
+flow@host:~/src [130] $ true
+flow@host:~/src $
+```
+
+Typische Werte: `1` allgemeiner Fehler, `2` Syntaxfehler, `126` nicht ausführbar, `127` Befehl nicht gefunden, `128+n` durch Signal `n` beendet (`130` = Ctrl+C, `148` = mit Ctrl+Z angehalten unter Linux). Eine leere Eingabe ändert den Status nicht.
+
 ### Farben
 
 Der Prompt wird über die Umgebungsvariable `GOSH_COLORS` eingefärbt. Sie besteht aus durch `:` getrennten Einträgen `schlüssel=code`:
@@ -267,6 +317,7 @@ Der Prompt wird über die Umgebungsvariable `GOSH_COLORS` eingefärbt. Sie beste
 | `user`    | `user@host`                    | `1;32` (fett grün)  |
 | `root`    | `user@host`, wenn man root ist | `1;31` (fett rot)   |
 | `path`    | aktuelles Verzeichnis          | `1;34` (fett blau)  |
+| `error`   | Exit-Status `[N]` nach einem Fehler | `1;31` (fett rot) |
 
 Die Werte sind [ANSI-SGR-Codes](https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_(Select_Graphic_Rendition)_parameters), mehrere werden mit `;` kombiniert:
 
@@ -304,6 +355,9 @@ GOSH_COLORS='user=1;38;2;136;192;208:path=38;2;216;222;233'
 # Ozean: türkis und kursiv blau
 GOSH_COLORS='user=1;96:path=3;94'
 
+# Fehler-Status gelb auf rotem Hintergrund
+GOSH_COLORS='error=1;33;41'
+
 # Root-Warnung: weiß auf rotem Hintergrund
 GOSH_COLORS='root=1;97;41'
 

brace.go

@@ -0,0 +1,268 @@
+package main
+
+// Brace expansion like in bash: a{b,c}d becomes abd acd, {1..5} becomes
+// 1 2 3 4 5. It happens first, on the text of the command line, so that the
+// resulting words go through the other expansions (~, variables, wildcards).
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// maxBraceWords limits the number of words a single word may expand to.
+const maxBraceWords = 100000
+
+// expandBraceWords applies brace expansion to every word of a command (the
+// text of a pipeline). Quoted or escaped braces and ${...} are left alone.
+// A redirection target must expand to a single word.
+func expandBraceWords(input string) (string, error) {
+	var (
+		out           strings.Builder
+		afterRedirect bool // the next word is the target of a redirection
+	)
+
+	for i := 0; i < len(input); {
+		ch := input[i]
+		switch {
+		case ch == ' ' || ch == '\t' || ch == '\n':
+			out.WriteByte(ch)
+			i++
+		case strings.IndexByte(";&|<>", ch) >= 0:
+			if ch == '<' || ch == '>' {
+				afterRedirect = true
+			}
+			out.WriteByte(ch)
+			i++
+		case ch == '#':
+			// A comment, until the end of the line
+			out.WriteString(input[i:])
+			return out.String(), nil
+		default:
+			end := wordEnd(input, i)
+			words, err := expandBraces(input[i:end])
+			if err != nil {
+				return "", err
+			}
+			if afterRedirect && len(words) > 1 {
+				return "", fmt.Errorf("%s: ambiguous redirect", sanitize(input[i:end]))
+			}
+			afterRedirect = false
+			out.WriteString(strings.Join(words, " "))
+			i = end
+		}
+	}
+	return out.String(), nil
+}
+
+// wordEnd returns the end of the word starting at i: the next unquoted blank
+// or operator character.
+func wordEnd(s string, i int) int {
+	var quote byte
+	for ; i < len(s); i++ {
+		ch := s[i]
+		switch {
+		case quote == '\'':
+			if ch == '\'' {
+				quote = 0
+			}
+		case ch == '\\':
+			i++
+		case ch == '$' && i+1 < len(s) && s[i+1] == '{':
+			if j := strings.IndexByte(s[i:], '}'); j >= 0 {
+				i += j
+			}
+		case quote == '"':
+			if ch == '"' {
+				quote = 0
+			}
+		case ch == '"' || ch == '\'':
+			quote = ch
+		case strings.IndexByte(" \t\n;&|<>", ch) >= 0:
+			return i
+		}
+	}
+	return len(s)
+}
+
+// braceScan calls fn for every unquoted, unescaped character of s that is
+// not part of a ${...} reference, with its index and the brace depth.
+// Scanning stops when fn returns false.
+func braceScan(s string, fn func(i, depth int) bool) {
+	var quote byte
+	depth := 0
+	for i := 0; i < len(s); i++ {
+		ch := s[i]
+		switch {
+		case quote == '\'':
+			if ch == '\'' {
+				quote = 0
+			}
+			continue
+		case ch == '\\':
+			i++
+			continue
+		case ch == '$' && i+1 < len(s) && s[i+1] == '{':
+			if j := strings.IndexByte(s[i:], '}'); j >= 0 {
+				i += j
+			}
+			continue
+		case quote == '"':
+			if ch == '"' {
+				quote = 0
+			}
+			continue
+		case ch == '"' || ch == '\'':
+			quote = ch
+			continue
+		}
+		if ch == '}' {
+			depth--
+		}
+		if !fn(i, depth) {
+			return
+		}
+		if ch == '{' {
+			depth++
+		}
+	}
+}
+
+// expandBraces expands the first valid brace expression of a word and then
+// recursively the results: a{b,c}d -> abd acd, x{1..3} -> x1 x2 x3. A brace
+// expression is valid if it contains an unquoted comma at its top level or
+// is a sequence; other braces ({}, {a}, ${x}) are kept as they are.
+func expandBraces(word string) ([]string, error) {
+	// Find the candidates: unquoted { with their matching }
+	var opens []int
+	pairs := map[int]int{}
+	braceScan(word, func(i, depth int) bool {
+		switch word[i] {
+		case '{':
+			opens = append(opens, i)
+		case '}':
+			if len(opens) > 0 {
+				pairs[opens[len(opens)-1]] = i
+				opens = opens[:len(opens)-1]
+			}
+		}
+		return true
+	})
+
+	for start := 0; start < len(word); start++ {
+		end, ok := pairs[start]
+		if !ok {
+			continue
+		}
+		inner := word[start+1 : end]
+		alternatives := splitTopLevelCommas(inner)
+		if len(alternatives) < 2 {
+			seq, ok, err := braceSequence(inner)
+			if err != nil {
+				return nil, err
+			}
+			if !ok {
+				continue
+			}
+			alternatives = seq
+		}
+
+		prefix, suffix := word[:start], word[end+1:]
+		var words []string
+		for _, alt := range alternatives {
+			expanded, err := expandBraces(prefix + alt + suffix)
+			if err != nil {
+				return nil, err
+			}
+			words = append(words, expanded...)
+			if len(words) > maxBraceWords {
+				return nil, errors.New("brace expansion: too many words")
+			}
+		}
+		return words, nil
+	}
+	return []string{word}, nil
+}
+
+// splitTopLevelCommas splits s at its unquoted commas that are not inside
+// nested braces.
+func splitTopLevelCommas(s string) []string {
+	var parts []string
+	last := 0
+	braceScan(s, func(i, depth int) bool {
+		if s[i] == ',' && depth == 0 {
+			parts = append(parts, s[last:i])
+			last = i + 1
+		}
+		return true
+	})
+	return append(parts, s[last:])
+}
+
+// braceSequence expands a sequence expression: x..y or x..y..step with
+// integers (zero-padded to the same width if one of them has a leading zero)
+// or single letters. ok is false if s is no sequence.
+func braceSequence(s string) (words []string, ok bool, err error) {
+	parts := strings.Split(s, "..")
+	if len(parts) != 2 && len(parts) != 3 {
+		return nil, false, nil
+	}
+	step := 1
+	if len(parts) == 3 {
+		step, err = strconv.Atoi(parts[2])
+		if err != nil {
+			return nil, false, nil
+		}
+		if step < 0 {
+			step = -step
+		}
+		if step == 0 {
+			step = 1
+		}
+	}
+
+	from, errFrom := strconv.Atoi(parts[0])
+	to, errTo := strconv.Atoi(parts[1])
+	isLetter := func(p string) bool {
+		return len(p) == 1 && (p[0] >= 'a' && p[0] <= 'z' || p[0] >= 'A' && p[0] <= 'Z')
+	}
+	format := func(n int) string { return strconv.Itoa(n) }
+	switch {
+	case errFrom == nil && errTo == nil:
+		// {01..10}: pad to the width of the longer number
+		if hasLeadingZero(parts[0]) || hasLeadingZero(parts[1]) {
+			width := max(len(parts[0]), len(parts[1]))
+			format = func(n int) string {
+				if n < 0 {
+					return fmt.Sprintf("-%0*d", width-1, -n)
+				}
+				return fmt.Sprintf("%0*d", width, n)
+			}
+		}
+	case isLetter(parts[0]) && isLetter(parts[1]):
+		from, to = int(parts[0][0]), int(parts[1][0])
+		format = func(n int) string { return string(rune(n)) }
+	default:
+		return nil, false, nil
+	}
+
+	count := (max(from, to)-min(from, to))/step + 1
+	if count > maxBraceWords {
+		return nil, false, errors.New("brace expansion: too many words")
+	}
+	if to < from {
+		step = -step
+	}
+	for n := from; (step > 0 && n <= to) || (step < 0 && n >= to); n += step {
+		words = append(words, format(n))
+	}
+	return words, true, nil
+}
+
+// hasLeadingZero reports whether a number is written with a leading zero
+// (01, -05), which makes a sequence zero-padded.
+func hasLeadingZero(s string) bool {
+	s = strings.TrimPrefix(s, "-")
+	return len(s) > 1 && s[0] == '0'
+}

brace_test.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestExpandBraces(t *testing.T) {
+	tests := []struct {
+		word string
+		want []string
+	}{
+		{"a{b,c}d", []string{"abd", "acd"}},
+		{"{a,b}{1,2}", []string{"a1", "a2", "b1", "b2"}},
+		{"x{a,{b,c}}y", []string{"xay", "xby", "xcy"}},
+		{"file{,.bak}", []string{"file", "file.bak"}},
+		{"{1..5}", []string{"1", "2", "3", "4", "5"}},
+		{"{3..1}", []string{"3", "2", "1"}},
+		{"{1..10..3}", []string{"1", "4", "7", "10"}},
+		{"{10..1..-4}", []string{"10", "6", "2"}},
+		{"{01..10..4}", []string{"01", "05", "09"}},
+		{"{8..010..1}", []string{"008", "009", "010"}},
+		{"{-2..2}", []string{"-2", "-1", "0", "1", "2"}},
+		{"{-01..1}", []string{"-01", "000", "001"}},
+		{"{a..e}", []string{"a", "b", "c", "d", "e"}},
+		{"{C..A}", []string{"C", "B", "A"}},
+		{"*.{go,md}", []string{"*.go", "*.md"}},
+		{`{"a b",c}`, []string{`"a b"`, "c"}},
+		{`{a\,b,c}`, []string{`a\,b`, "c"}},
+		{"{$HOME,~}/x", []string{"$HOME/x", "~/x"}},
+		// Not expanded: quoted, escaped, no comma, ${...}, invalid sequences
+		{`"{a,b}"`, []string{`"{a,b}"`}},
+		{`'{a,b}'`, []string{`'{a,b}'`}},
+		{`\{a,b\}`, []string{`\{a,b\}`}},
+		{"{a}", []string{"{a}"}},
+		{"{}", []string{"{}"}},
+		{"{a,b", []string{"{a,b"}},
+		{"a,b}", []string{"a,b}"}},
+		{"${HOME}", []string{"${HOME}"}},
+		{"${X:-a,b}", []string{"${X:-a,b}"}},
+		{"{a..1}", []string{"{a..1}"}},
+		{"{1..2..x}", []string{"{1..2..x}"}},
+		{"{ab..cd}", []string{"{ab..cd}"}},
+		// An invalid brace before a valid one
+		{"{a}{b,c}", []string{"{a}b", "{a}c"}},
+	}
+	for _, tc := range tests {
+		got, err := expandBraces(tc.word)
+		if err != nil {
+			t.Errorf("expandBraces(%q) returned error: %v", tc.word, err)
+			continue
+		}
+		if !reflect.DeepEqual(got, tc.want) {
+			t.Errorf("expandBraces(%q) = %q, want %q", tc.word, got, tc.want)
+		}
+	}
+
+	if _, err := expandBraces("{1..1000000}"); err == nil {
+		t.Error("expected an error for a too large sequence")
+	}
+	if _, err := expandBraces("{1..11}{1..100}{1..100}"); err == nil {
+		t.Error("expected an error for too many words")
+	}
+}
+
+func TestExpandBraceWords(t *testing.T) {
+	tests := []struct {
+		input, want string
+	}{
+		{"echo a{b,c} d", "echo ab ac d"},
+		{"echo {1..3}|wc -w", "echo 1 2 3|wc -w"},
+		{"echo a > {f}", "echo a > {f}"},
+		{"echo {a,b} 2>&1", "echo a b 2>&1"},
+		{"echo x # {a,b}", "echo x # {a,b}"},
+		{`echo "{a,b} c" {d,e}`, `echo "{a,b} c" d e`},
+	}
+	for _, tc := range tests {
+		got, err := expandBraceWords(tc.input)
+		if err != nil || got != tc.want {
+			t.Errorf("expandBraceWords(%q) = %q, %v; want %q", tc.input, got, err, tc.want)
+		}
+	}
+
+	for _, input := range []string{"echo a > {f,g}", "cat < x{1..2}", "echo a 2>> {a,b}"} {
+		if _, err := expandBraceWords(input); err == nil || !strings.Contains(err.Error(), "ambiguous redirect") {
+			t.Errorf("expandBraceWords(%q): %v, want ambiguous redirect", input, err)
+		}
+	}
+}
+
+func TestExecInput_BraceExpansion(t *testing.T) {
+	origDir, _ := os.Getwd()
+	defer os.Chdir(origDir)
+	dir := t.TempDir()
+	os.Chdir(dir)
+
+	if err := execInput("mkdir -p d/{x,y}/{1..2} && touch d/x/1/f{a,b}.txt"); err != nil {
+		t.Fatal(err)
+	}
+	for _, path := range []string{"d/x/1", "d/x/2", "d/y/1", "d/y/2", "d/x/1/fa.txt", "d/x/1/fb.txt"} {
+		if _, err := os.Stat(path); err != nil {
+			t.Errorf("%s was not created", path)
+		}
+	}
+
+	// Brace expansion comes before wildcards and variables
+	t.Setenv("GOSH_BRACE", "v")
+	execInput("echo d/x/1/*.{txt,go} {${GOSH_BRACE},w}1 > out")
+	if got, _ := os.ReadFile("out"); string(got) != "d/x/1/fa.txt d/x/1/fb.txt d/x/1/*.go v1 w1\n" {
+		t.Errorf("out = %q", got)
+	}
+
+	if err := execInput("echo a > {f,g}"); err == nil || lastStatus != 1 {
+		t.Errorf("ambiguous redirect: %v, $? = %d", err, lastStatus)
+	}
+}

jobs.go

@@ -162,9 +162,7 @@ func (j *job) update(pid int, ws syscall.WaitStatus) {
 		switch {
 		case ws.Stopped():
 			p.stopped = true
-		case ws.Continued():
+		case ws.Exited() || ws.Signaled():
-			p.stopped = false
-		default:
 			p.finished, p.stopped = true, false
 			p.err = waitStatusError(ws)
 			p.cmd.Process.Release()
@@ -185,17 +183,30 @@ func waitStatusError(ws syscall.WaitStatus) error {
 	return nil
 }
 
-// wait waits until no process of the job is running any more (all finished
+// waitFlags returns the options for wait4: WUNTRACED to see stopped
-// or, with job control, stopped). With nohang it only collects the status
+// processes (with job control) and WNOHANG to not block.
-// changes that are already available and does not block.
+//
-func (j *job) wait(nohang bool) {
+// WCONTINUED is not used: Go's syscall.WaitStatus decodes the "continued"
+// status wrongly on FreeBSD (as killed by SIGCONT) and macOS (as stopped).
+// The shell marks jobs as running itself when it continues them (fg, bg); a
+// job continued from outside (kill -CONT) stays "Stopped" in the job table
+// until it stops again or exits.
+func waitFlags(j *job, nohang bool) int {
 	flags := 0
 	if jobControl && j.pgid != 0 {
-		flags |= syscall.WUNTRACED | syscall.WCONTINUED
+		flags |= syscall.WUNTRACED
 	}
 	if nohang {
 		flags |= syscall.WNOHANG
 	}
+	return flags
+}
+
+// wait waits until no process of the job is running any more (all finished
+// or, with job control, stopped). With nohang it only collects the status
+// changes that are already available and does not block.
+func (j *job) wait(nohang bool) {
+	flags := waitFlags(j, nohang)
 
 	for {
 		// With job control all processes of the job are in its process

jobs_linux_test.go

@@ -105,6 +105,21 @@ func (s *ptyShell) expect(want string) {
 	s.t.Fatalf("timeout waiting for %q, output:\n%s", want, s.out.String())
 }
 
+func TestWaitFlags_NoWCONTINUED(t *testing.T) {
+	defer func(saved bool) { jobControl = saved }(jobControl)
+	jobControl = true
+	j := &job{pgid: 1}
+	for _, nohang := range []bool{false, true} {
+		flags := waitFlags(j, nohang)
+		if flags&syscall.WCONTINUED != 0 {
+			t.Errorf("waitFlags(nohang=%v) contains WCONTINUED, which Go decodes wrongly on BSD", nohang)
+		}
+		if flags&syscall.WUNTRACED == 0 {
+			t.Errorf("waitFlags(nohang=%v) misses WUNTRACED", nohang)
+		}
+	}
+}
+
 func TestJobControl(t *testing.T) {
 	s := startPtyShell(t)
 
@@ -120,6 +135,13 @@ func TestJobControl(t *testing.T) {
 	s.send("bg\n")
 	s.expect("[1]+  Running                 sleep 30 &")
 
+	// After bg the job keeps running and is not reported as finished
+	// (regression: on FreeBSD the "continued" status was read as killed by
+	// SIGCONT, "Exit 147")
+	time.Sleep(300 * time.Millisecond)
+	s.send("jobs\n")
+	s.expect("[1]+  Running                 sleep 30 &")
+
 	// fg brings it back, Ctrl+C reaches only the job
 	s.send("fg %1\n")
 	s.expect("sleep 30")

main.go

@@ -612,7 +612,7 @@ func getPrompt() string {
 		c := parseColors(os.Getenv("GOSH_COLORS"))
 		colors = &c
 	}
-	return buildPrompt(username, hostname, wd, os.Geteuid() == 0, colors)
+	return buildPrompt(username, hostname, wd, os.Geteuid() == 0, lastStatus, colors)
 }
 
 // promptColors holds the SGR parameters (e.g. "1;32") for the parts of the
@@ -621,12 +621,14 @@ type promptColors struct {
 	user  string // user@host
 	root  string // user@host when running as root
 	path  string // working directory
+	error string // exit status of the last command, if it failed
 }
 
-// defaultColors: bold green user, bold red root, bold blue directory
+// defaultColors: bold green user, bold red root, bold blue directory, bold
-var defaultColors = promptColors{user: "1;32", root: "1;31", path: "1;34"}
+// red exit status
+var defaultColors = promptColors{user: "1;32", root: "1;31", path: "1;34", error: "1;31"}
 
-// parseColors reads a GOSH_COLORS value like "user=1;33:root=1;31:path=36"
+// parseColors reads a GOSH_COLORS value like "user=1;33:path=36:error=31"
 // and overrides the corresponding defaults. Unknown keys and values that are
 // not plain SGR parameters (digits and ';') are ignored, so the variable
 // cannot be used to write arbitrary escape sequences to the terminal.
@@ -644,6 +646,8 @@ func parseColors(spec string) promptColors {
 			colors.root = value
 		case "path":
 			colors.path = value
+		case "error":
+			colors.error = value
 		}
 	}
 	return colors
@@ -669,20 +673,28 @@ func colorize(text, sgr string) string {
 	return "\x1b[" + sgr + "m" + text + "\x1b[0m"
 }
 
-// buildPrompt formats the prompt as user@host:path $. The parts are sanitized
+// buildPrompt formats the prompt as user@host:path $, or user@host:path [N] $
+// if the last command failed with exit status N. The parts are sanitized
 // before the color codes are added, so only our own escape sequences end up
 // in the prompt. colors == nil disables colors.
-func buildPrompt(username, hostname, path string, root bool, colors *promptColors) string {
+func buildPrompt(username, hostname, path string, root bool, status int, colors *promptColors) string {
 	userHost := sanitize(username + "@" + hostname)
 	path = sanitize(path)
+	var failed string
+	if status != 0 {
+		failed = " [" + strconv.Itoa(status) + "]"
+	}
 	if colors == nil {
-		return userHost + ":" + path + " $ "
+		return userHost + ":" + path + failed + " $ "
 	}
 	userColor := colors.user
 	if root {
 		userColor = colors.root
 	}
-	return colorize(userHost, userColor) + ":" + colorize(path, colors.path) + " $ "
+	if failed != "" {
+		failed = " " + colorize(failed[1:], colors.error)
+	}
+	return colorize(userHost, userColor) + ":" + colorize(path, colors.path) + failed + " $ "
 }
 
 // useColor reports whether the prompt should be colored: stdout must be a
@@ -815,7 +827,7 @@ func currentWord(s string) (word string, start int, quote byte) {
 func escapeWord(s string) string {
 	var b strings.Builder
 	for _, r := range s {
-		if strings.ContainsRune(" \t\\'\";|&<>*?[$", r) {
+		if strings.ContainsRune(" \t\\'\";|&<>*?[${", r) {
 			b.WriteByte('\\')
 		}
 		b.WriteRune(r)
@@ -1354,6 +1366,12 @@ func execInput(input string) error {
 // 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
+	input, err := expandBraceWords(input)
+	if err != nil {
+		return err
+	}
+
 	// Split the input into words and operators, expanding variables and ~ on
 	// the way.
 	tokens, err := tokenize(input)
@@ -1783,13 +1801,17 @@ Features:
     override with $GOSH_HISTFILE); lines starting with a space are not saved
   - Tab completion for commands and file paths
   - Tilde expansion (~, ~/path) at the start of unquoted words
+  - Brace expansion: a{b,c}d -> abd acd, {1..5}, {01..10..2}, {a..e}
   - Wildcards: * ? [abc] [a-z] [!abc] match file names (not hidden files
     unless the pattern starts with a dot); quoted wildcards and values of
     variables are not expanded, a pattern without match is kept as is
-  - Colored prompt (user@host green, red for root; directory blue),
+  - Prompt user@host:dir $, with [N] before the $ if the last command
-    configurable with $GOSH_COLORS, e.g. GOSH_COLORS='user=1;33:path=36'
+    failed with exit status N
-    (keys user, root, path; values are ANSI SGR codes, empty = no color);
+  - Colored prompt (user@host green, red for root; directory blue; exit
-    disabled with $NO_COLOR, TERM=dumb or when output is not a terminal
+    status red), configurable with $GOSH_COLORS, e.g.
+    GOSH_COLORS='user=1;33:path=36' (keys user, root, path, error; values
+    are ANSI SGR codes, empty = no color); disabled with $NO_COLOR,
+    TERM=dumb or when output is not a terminal
   - Environment variable expansion ($VAR, ${VAR}, ${VAR:-default});
     using an unset variable is an error, use ${VAR:-} for an empty default
   - Command lists: a ; b (run both), a && b (b only if a succeeded),

main_test.go

@@ -1054,24 +1054,24 @@ func TestGetPrompt_EscapesControlCharacters(t *testing.T) {
 }
 
 func TestBuildPrompt_Color(t *testing.T) {
-	got := buildPrompt("flow", "host", "~/src", false, &defaultColors)
+	got := buildPrompt("flow", "host", "~/src", false, 0, &defaultColors)
 	want := "\x1b[1;32mflow@host\x1b[0m:\x1b[1;34m~/src\x1b[0m $ "
 	if got != want {
 		t.Errorf("buildPrompt() = %q, want %q", got, want)
 	}
 
-	got = buildPrompt("root", "host", "/", true, &defaultColors)
+	got = buildPrompt("root", "host", "/", true, 0, &defaultColors)
 	if !strings.HasPrefix(got, "\x1b[1;31mroot@host") {
 		t.Errorf("expected red user for root, got %q", got)
 	}
 
-	got = buildPrompt("flow", "host", "~/src", false, nil)
+	got = buildPrompt("flow", "host", "~/src", false, 0, nil)
 	if got != "flow@host:~/src $ " {
 		t.Errorf("buildPrompt() without color = %q", got)
 	}
 
 	colors := promptColors{user: "38;5;208", path: ""}
-	got = buildPrompt("flow", "host", "~/src", false, &colors)
+	got = buildPrompt("flow", "host", "~/src", false, 0, &colors)
 	if got != "\x1b[38;5;208mflow@host\x1b[0m:~/src $ " {
 		t.Errorf("buildPrompt() with custom colors = %q", got)
 	}
@@ -1083,13 +1083,14 @@ func TestParseColors(t *testing.T) {
 		want promptColors
 	}{
 		{"", defaultColors},
-		{"user=1;33", promptColors{user: "1;33", root: "1;31", path: "1;34"}},
+		{"user=1;33", promptColors{user: "1;33", root: "1;31", path: "1;34", error: "1;31"}},
-		{"user=33:root=41;97:path=38;5;208", promptColors{user: "33", root: "41;97", path: "38;5;208"}},
+		{"user=33:root=41;97:path=38;5;208", promptColors{user: "33", root: "41;97", path: "38;5;208", error: "1;31"}},
-		{"path=", promptColors{user: "1;32", root: "1;31", path: ""}},
+		{"error=33", promptColors{user: "1;32", root: "1;31", path: "1;34", error: "33"}},
+		{"path=", promptColors{user: "1;32", root: "1;31", path: "", error: "1;31"}},
 		{"path=0m\x1b[2J", defaultColors}, // escape sequences are rejected
 		{"path=red", defaultColors},       // only numeric codes
 		{"foo=1:user", defaultColors},     // unknown key, missing value
-		{"user=35::path=36", promptColors{user: "35", root: "1;31", path: "36"}},
+		{"user=35::path=36", promptColors{user: "35", root: "1;31", path: "36", error: "1;31"}},
 	}
 	for _, tc := range tests {
 		if got := parseColors(tc.spec); got != tc.want {
@@ -1098,8 +1099,27 @@ func TestParseColors(t *testing.T) {
 	}
 }
 
+func TestBuildPrompt_Status(t *testing.T) {
+	if got := buildPrompt("flow", "host", "~", false, 0, nil); got != "flow@host:~ $ " {
+		t.Errorf("status 0: %q", got)
+	}
+	if got := buildPrompt("flow", "host", "~", false, 127, nil); got != "flow@host:~ [127] $ " {
+		t.Errorf("status 127 without color: %q", got)
+	}
+	got := buildPrompt("flow", "host", "~", false, 1, &defaultColors)
+	want := "\x1b[1;32mflow@host\x1b[0m:\x1b[1;34m~\x1b[0m \x1b[1;31m[1]\x1b[0m $ "
+	if got != want {
+		t.Errorf("status 1 with color = %q, want %q", got, want)
+	}
+	colors := defaultColors
+	colors.error = ""
+	if got := buildPrompt("flow", "host", "~", false, 2, &colors); !strings.HasSuffix(got, " [2] $ ") {
+		t.Errorf("status without error color = %q", got)
+	}
+}
+
 func TestBuildPrompt_ColorEscapesControlCharacters(t *testing.T) {
-	got := buildPrompt("flow", "host", "evil\x1b[2J\x07", false, &defaultColors)
+	got := buildPrompt("flow", "host", "evil\x1b[2J\x07", false, 0, &defaultColors)
 	if strings.Contains(got, "\x1b[2J") || strings.Contains(got, "\x07") {
 		t.Errorf("prompt contains control characters from path: %q", got)
 	}