Changes to examples/fwwc/main.go. All files

examples/fwwc/main.go

new file mode 100644@@ -0,0 +1,134 @@+// fwwc is a an example program that recursively walks directories and+// prints the number of lines in each file it encounters.+package main++import (+	"bytes"+	"flag"+	"fmt"+	"io"+	"io/fs"+	"os"+	"path/filepath"++	"github.com/charlievieth/fastwalk"+)++var newLine = []byte{'\n'}++// countLinesInFile returns the number of newlines ('\n') in file name.+func countLinesInFile(name string) (int64, error) {+	f, err := os.Open(name)+	if err != nil {+		return 0, err+	}+	defer f.Close()++	buf := make([]byte, 16*1024)+	var lines int64+	for {+		n, e := f.Read(buf)+		if n > 0 {+			lines += int64(bytes.Count(buf[:n], newLine))+		}+		if e != nil {+			if e != io.EOF {+				err = e+			}+			break+		}+	}+	return lines, err+}++func LineCount(root string, followLinks bool) error {+	countLinesWalkFn := func(path string, d fs.DirEntry, err error) error {+		// We wrap this with fastwalk.IgnorePermissionErrors so we know the+		// error is not a permission error (common when walking outside a users+		// home directory) and is likely something worse so we should return it+		// and abort the walk.+		//+		// A common error here is "too many open files", which can occur if the+		// walkFn opens, but does not close, files.+		if err != nil {+			return err+		}++		// If the entry is a symbolic link get the type of file that+		// it references.+		typ := d.Type()+		if typ&fs.ModeSymlink != 0 {+			if fi, err := fastwalk.StatDirEntry(path, d); err == nil {+				typ = fi.Mode().Type()+			}+		}++		// Skip dot (".") files (but allow "." / PWD as the path)+		if path != "." && typ.IsDir() {+			name := d.Name()+			if name == "" || name[0] == '.' || name[0] == '_' {+				return fastwalk.SkipDir+			}+			return nil+		}+		if typ.IsRegular() {+			lines, err := countLinesInFile(path)+			if err == nil {+				fmt.Printf("%8d %s\n", lines, path)+			} else {+				// Print but do not return the error.+				fmt.Fprintf(os.Stderr, "%s: %s\n", path, err)+			}+		}+		return nil+	}++	// Ignore permission errors traversing directories.+	//+	// Note: this only ignores permission errors when traversing directories.+	// Permission errors may still be encountered when accessing files.+	walkFn := fastwalk.IgnorePermissionErrors(countLinesWalkFn)++	conf := fastwalk.Config{+		// Safely follow symbolic links. This can also be achieved by+		// wrapping walkFn with fastwalk.FollowSymlinks().+		Follow: followLinks,++		// If NumWorkers is ≤ 0 the default is used, which is sufficient+		// for most use cases.+	}+	// Note: Walk can also be called with a nil Config, in which case+	// fastwalk.DefaultConfig is used.+	if err := fastwalk.Walk(&conf, root, walkFn); err != nil {+		return fmt.Errorf("walking directory %s: %w", root, err)+	}+	return nil+}++const UsageMsg = `Usage: %[1]s [-L] [PATH...]:++%[1]s prints the number of lines in each file it finds,+ignoring directories that start with '.' or '_'.++`++func main() {+	flag.Usage = func() {+		fmt.Fprintf(os.Stdout, UsageMsg, filepath.Base(os.Args[0]))+		flag.PrintDefaults()+	}+	followLinks := flag.Bool("L", false, "Follow symbolic links")+	flag.Parse()++	args := flag.Args()+	if len(args) == 0 {+		args = append(args, ".")+	}+	for _, root := range args {+		// fmt.Println("ROOT:", root)+		if err := LineCount(root, *followLinks); err != nil {+			fmt.Fprintln(os.Stderr, "error:", err)+			os.Exit(1)+		}+	}+}