README: guard the daily cron scan against an unmounted disk (closes #175)

A disk that is not mounted leaves its mount point an empty directory.
scan then deletes every record under it, and the next scan reads every
file again. The README now says so. Its cron line runs scan only when
mountpoint finds the disks mounted, and one sentence says which mount
points to test.

Model: opus-5-5

README.md

@@ -114,15 +114,20 @@ docker run --rm -v /srv:/srv:ro -v /var/lib/sfdupes:/var/lib/sfdupes \
 Run `scan` as root, so that it can read every file. `scan` warns about a
 directory it cannot read, and about a new or changed file it cannot read. It
 skips the path and deletes the records at or below it (see "Rules for the
-walk"). As the file `/etc/cron.d/sfdupes`:
+walk").
+
+An unmounted disk leaves its mount point empty, so `scan` deletes every record
+under it, and the next scan reads every file on the disk again. Test the mount
+point of each disk at or below `/srv` with its own `mountpoint -q`, joined with
+`&&`, and test `/srv` only when it is one. As the file `/etc/cron.d/sfdupes`:
 
 ```
-30 3 * * * root /usr/local/bin/sfdupes scan /srv 2>>/var/log/sfdupes.log || tail -n 3 /var/log/sfdupes.log
+30 3 * * * root if mountpoint -q /srv; then /usr/local/bin/sfdupes scan /srv 2>>/var/log/sfdupes.log || tail -n 3 /var/log/sfdupes.log; else echo "a disk is not mounted; scan of /srv skipped"; fi
 ```
 
 - The first scan creates `/var/lib/sfdupes/db.sqlite` and its directory. To keep
-  the database elsewhere, put `SFDUPES_DATABASE=/path/to/db.sqlite` before the
+  the database elsewhere, put `SFDUPES_DATABASE=/path/to/db.sqlite` directly
-  command on the same line.
+  before `/usr/local/bin/sfdupes`.
 - `scan` writes nothing to stdout. Its stderr, appended here to
   `/var/log/sfdupes.log`, holds:
     - one line naming the database;
@@ -1201,14 +1206,6 @@ On a terminal:
     ⠹ [3/4] hash: [12345/98765], 92 files/s, elapsed 2m32s, remain 17m44s            12% |█         |
     ```
 
-- During `scan`'s `walk`, the line below the display shows the path of the last
-  file the walk found. Each draw shows the path of that moment, cut short before
-  the terminal's last column. The path is escaped as in the reports (see "Report
-  output format"). Each control character left after that is written as `\x` and
-  its code in two hexadecimal digits, such as `\x1b` for the escape character. A
-  control character is one that a terminal acts on instead of showing. The line
-  is erased when the walk ends, and the next phase is drawn on it.
-
 - No line reaches the terminal's last column. A line too wide for the terminal
   first leaves out its rate, the words of a stalled phase, or what the phase is
   waiting for. It leaves out its bar next. It is cut short at the edge only when

go.mod

@@ -3,7 +3,6 @@ module sneak.berlin/go/sfdupes
 go 1.25.7
 
 require (
-	github.com/rivo/uniseg v0.4.7
 	github.com/schollz/progressbar/v3 v3.19.1
 	github.com/spf13/cobra v1.10.2
 	golang.org/x/sys v0.46.0
@@ -19,6 +18,7 @@ require (
 	github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	modernc.org/libc v1.74.1 // indirect
 	modernc.org/mathutil v1.7.1 // indirect

internal/sfdupes/progress.go

@@ -9,10 +9,8 @@ import (
 	"strings"
 	"sync"
 	"time"
-	"unicode"
 	"unicode/utf8"
 
-	"github.com/rivo/uniseg"
 	"github.com/schollz/progressbar/v3"
 	"golang.org/x/term"
 )
@@ -118,8 +116,7 @@ type drawnCount struct {
 // terminal's width. A phase with an exact total ends the line with its
 // percent and bar, at the terminal's right edge, when the terminal has
 // room for them. It is drawn again every redrawInterval, so its elapsed
-// time keeps moving while the phase waits for its next item. Each draw
+// time keeps moving while the phase waits for its next item. When
-// of the walk shows the path it reached last on the line below. When
 // stderr is not a TTY it emits no ANSI redraws: it prints line as the
 // phase starts, every plainInterval while it runs, and as it ends.
 //
@@ -144,7 +141,6 @@ type progress struct {
 	estimate   bool
 	waitingFor string
 	stalledOn  string
-	path       string // the path the walk reached last; "" for none
 	count      int64
 	start      time.Time // when the phase started, for the elapsed time
 	rateStart  time.Time // when the count started, for the time remaining
@@ -243,82 +239,6 @@ func (p *progress) draw() {
 	// less the terminal's last column, which spinnerMargin keeps clear. A
 	// bar's cells take one column each but more than one byte.
 	p.widest = max(p.widest, utf8.RuneCountInString(text)+spinnerMargin-1)
-
-	if p.path != "" {
-		// The library draws the path on the line below and returns to
-		// the phase's line. The path is escaped as warnings are, and its
-		// other control characters are written out, so that the terminal
-		// shows them instead of acting on them. It stays clear of the
-		// last column, so that no terminal wraps it.
-		shown := escapeControlChars(escapePath(p.path))
-		_ = p.bar.AddDetail(cutToColumns(shown, width-1))
-	}
-}
-
-// escapeControlChars returns s with each control character written as
-// \x and its code in two hex digits, as \x1b for the escape character.
-// The control characters are U+0000 to U+001F, U+007F and U+0080 to
-// U+009F, as unicode.IsControl reports them. A byte from 0x80 to 0x9F
-// that is not part of a valid UTF-8 character is written the same way,
-// as \x9b, since a terminal not in UTF-8 mode acts on it. Every other
-// byte is kept as it is.
-func escapeControlChars(s string) string {
-	var b strings.Builder
-
-	for rest := s; rest != ""; {
-		char, size := utf8.DecodeRuneInString(rest)
-		if char == utf8.RuneError && size == 1 {
-			// Not part of a valid UTF-8 character. A terminal not in
-			// UTF-8 mode reads the byte as the character with its code,
-			// so that 0x9b is a control character there and 0xe9 is not.
-			char = rune(rest[0])
-		}
-
-		if unicode.IsControl(char) {
-			fmt.Fprintf(&b, `\x%02x`, char)
-		} else {
-			b.WriteString(rest[:size])
-		}
-
-		rest = rest[size:]
-	}
-
-	return b.String()
-}
-
-// cutToColumns returns s cut to at most columns terminal columns, at a
-// character boundary. A wide character, as in Chinese, takes two
-// columns.
-func cutToColumns(s string, columns int) string {
-	used, end, state := 0, 0, -1
-
-	for rest := s; rest != ""; {
-		char, next, width, nextState := uniseg.FirstGraphemeClusterInString(
-			rest, state)
-		if used+width > columns {
-			break
-		}
-
-		used += width
-		end += len(char)
-		rest, state = next, nextState
-	}
-
-	return s[:end]
-}
-
-// clear erases the display from the terminal: its line, and the path on
-// the line below when one is shown. p.mu must be held.
-func (p *progress) clear() {
-	if p.bar == nil {
-		return
-	}
-
-	if p.path != "" {
-		_ = p.bar.AddDetail("")
-	}
-
-	_ = p.bar.Clear()
 }
 
 // newBar has the library make what draw draws: its spinner, followed by
@@ -343,8 +263,6 @@ func (p *progress) newBar(width int) {
 		// The text carries the elapsed time and the time remaining.
 		progressbar.OptionSetElapsedTime(false),
 		progressbar.OptionSetPredictTime(false),
-		// The line below the phase's line, for the walk's path.
-		progressbar.OptionSetMaxDetailRow(1),
 	)
 	p.widest = 0
 }
@@ -396,19 +314,6 @@ func (p *progress) increment() {
 	p.lastItem = now
 }
 
-// setPath records the path the walk reached last, which a display on a
-// terminal shows at its next draw.
-func (p *progress) setPath(path string) {
-	if p == nil {
-		return
-	}
-
-	p.mu.Lock()
-	defer p.mu.Unlock()
-
-	p.path = path
-}
-
 // warnf prints a one-line warning to stderr without corrupting the
 // display. The whole message is escaped like a report's path columns,
 // so a path holding a newline cannot split the warning.
@@ -422,9 +327,11 @@ func (p *progress) warnf(format string, args ...any) {
 	p.mu.Lock()
 	defer p.mu.Unlock()
 
-	// The warning takes the display's line; the next draw shows the
+	if p.bar != nil {
-	// display again, on the line below.
+		// The warning takes the display's line; the next draw shows
-	p.clear()
+		// the display again, on the line below.
+		_ = p.bar.Clear()
+	}
 
 	fmt.Fprintln(os.Stderr, msg)
 }
@@ -485,7 +392,9 @@ func (w *progressWriter) Flush() error {
 		w.p.mu.Lock()
 		defer w.p.mu.Unlock()
 
-		w.p.clear()
+		if w.p.bar != nil {
+			_ = w.p.bar.Clear()
+		}
 	}
 
 	_, err := w.out.Write(w.buf)
@@ -505,13 +414,6 @@ func (p *progress) finish() {
 	close(p.stop)
 	<-p.done
 
-	// The walk's path is only for someone watching the walk. Its line is
-	// erased, and the next phase is drawn on it.
-	p.mu.Lock()
-	p.clear()
-	p.path = ""
-	p.mu.Unlock()
-
 	p.draw()
 
 	if p.width != nil {

internal/sfdupes/progress_test.go

@@ -6,7 +6,6 @@ import (
 	"math"
 	"os"
 	"path/filepath"
-	"regexp"
 	"slices"
 	"strings"
 	"sync"
@@ -1139,164 +1138,3 @@ func TestWarningAfterLastItemKeepsBar(t *testing.T) {
 		t.Errorf("terminal shows %q, want a count of 2 of 2", shown)
 	}
 }
-
-func TestCutToColumns(t *testing.T) {
-	t.Parallel()
-
-	cases := []struct {
-		s       string
-		columns int
-		want    string
-	}{
-		{"/srv/a", 10, "/srv/a"},
-		{"/srv/photos", 8, "/srv/pho"},
-		// Each of these two fullwidth letters takes two columns.
-		{"/ＡＢ/a", 4, "/Ａ"},
-		{"/ＡＢ/a", 5, "/ＡＢ"},
-		// An accent that combines with the letter before stays with it.
-		{"/café/a", 5, "/café"},
-		{"/srv", 0, ""},
-	}
-
-	for _, tc := range cases {
-		if got := cutToColumns(tc.s, tc.columns); got != tc.want {
-			t.Errorf("cutToColumns(%q, %d) = %q, want %q",
-				tc.s, tc.columns, got, tc.want)
-		}
-	}
-}
-
-func TestEscapeControlChars(t *testing.T) {
-	t.Parallel()
-
-	cases := map[string]string{
-		"/srv/music":    "/srv/music",
-		"/a\x1b[2Jb":    `/a\x1b[2Jb`,
-		"/a\x00\a\x7fb": `/a\x00\x07\x7fb`,
-		// U+009B takes two bytes in UTF-8.
-		"/a\u009b2Jb": `/a\x9b2Jb`,
-		// Byte 0x9b alone is not valid UTF-8. A terminal not in UTF-8
-		// mode acts on it, as on every byte from 0x80 to 0x9f.
-		"/a\x9b2Jb":       `/a\x9b2Jb`,
-		"/a\x80\x9f\xa0b": `/a\x80\x9f` + "\xa0b",
-		// In ě, which is c4 9b in UTF-8, byte 0x9b is part of a valid
-		// character.
-		"/aě2Jb":          "/aě2Jb",
-		"/café/ＡＢ":        "/café/ＡＢ",
-		"/latin1-caf\xe9": "/latin1-caf\xe9",
-	}
-	for in, want := range cases {
-		if got := escapeControlChars(in); got != want {
-			t.Errorf("escapeControlChars(%q) = %q, want %q", in, got, want)
-		}
-	}
-}
-
-// pathLines returns the text of each line the library wrote below a
-// display's line. It writes one as an erase to the end of the line, a
-// carriage return, the text and a newline.
-func pathLines(out string) []string {
-	matches := regexp.MustCompile("\x1b\\[K\r([^\n]*)\n").
-		FindAllStringSubmatch(out, -1)
-	lines := make([]string, 0, len(matches))
-
-	for _, m := range matches {
-		lines = append(lines, m[1])
-	}
-
-	return lines
-}
-
-// TestTerminalWalkShowsPathBelow checks that the walk's display on a
-// terminal 30 columns wide shows the path it reached last on the line
-// below, cut to 29 columns. That line is erased before a warning is
-// printed, and again when the walk ends, so the next phase is drawn on
-// an empty line.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestTerminalWalkShowsPathBelow(t *testing.T) {
-	stderr := captureStderr(t)
-	p := startProgress(progressParams{
-		label: scanPhase("walk"), unit: scanUnit, total: -1,
-	}, func() int { return 30 }, testRedraw, time.Now)
-
-	const shown = "/srv/photos/2026/holiday/beac"
-
-	p.setPath("/srv/photos/2026/holiday/beach.jpg")
-	p.increment()
-	awaitOutput(t, stderr, shown, 1)
-
-	p.warnf("warning")
-
-	before, _, _ := strings.Cut(stderr(), "warning")
-	if lines := pathLines(before); lines[len(lines)-1] != "" {
-		t.Errorf("line below shows %q as the warning is printed, want it "+
-			"empty", lines[len(lines)-1])
-	}
-
-	// Drawn again below the warning.
-	awaitOutput(t, stderr, shown, strings.Count(before, shown)+1)
-	p.finish()
-
-	lines := pathLines(stderr())
-	if !slices.Contains(lines, shown) {
-		t.Errorf("lines below the display = %q, want %q among them",
-			lines, shown)
-	}
-
-	if last := lines[len(lines)-1]; last != "" {
-		t.Errorf("line below the display shows %q after the walk, want it "+
-			"empty", last)
-	}
-}
-
-// TestTerminalWalkEscapesControlChars checks that a walked path holding
-// escape characters, which would clear the screen and set the window
-// title, puts none on the line below the walk's display. The line shows
-// each control character written out, as \x1b.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestTerminalWalkEscapesControlChars(t *testing.T) {
-	stderr := captureStderr(t)
-	p := startProgress(progressParams{
-		label: scanPhase("walk"), unit: scanUnit, total: -1,
-	}, func() int { return 80 }, testRedraw, time.Now)
-
-	p.setPath("/srv/\x1b[2J\x1b]0;title\a/beach.jpg")
-	p.increment()
-	awaitOutput(t, stderr, "beach.jpg", 1)
-	p.finish()
-
-	lines := pathLines(stderr())
-	for _, line := range lines {
-		if strings.Contains(line, "\x1b") {
-			t.Errorf("line below the display = %q, want no escape "+
-				"character", line)
-		}
-	}
-
-	const shown = `/srv/\x1b[2J\x1b]0;title\x07/beach.jpg`
-	if !slices.Contains(lines, shown) {
-		t.Errorf("lines below the display = %q, want %q among them",
-			lines, shown)
-	}
-}
-
-// TestPlainWalkShowsNoPath checks that the walk's display prints no path
-// when stderr is not a terminal.
-//
-//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
-func TestPlainWalkShowsNoPath(t *testing.T) {
-	stderr := captureStderr(t)
-	p := startProgress(progressParams{
-		label: scanPhase("walk"), unit: scanUnit, total: -1,
-	}, nil, testRedraw, time.Now)
-
-	p.setPath("/srv/a")
-	p.increment()
-	p.finish()
-
-	if strings.Contains(stderr(), "/srv/a") {
-		t.Errorf("stderr = %q, want no path", stderr())
-	}
-}

internal/sfdupes/scan.go

@@ -562,7 +562,6 @@ func (s *scanState) walkPhase(events <-chan walkEvent, roots []string) {
 
 		s.st.walked++
 
-		prog.setPath(ev.rec.path)
 		prog.increment()
 
 		old, ok := s.existing[ev.rec.path]