Implement new option to avoid Bash argument amount limit

Also, include 'go.mod' file for a proper and modern local development

cmd/giashard/main.go

@@ -1,16 +1,18 @@
 package main
 
 import (
+	"bufio"
 	"errors"
-	"strings"
 	"flag"
 	"fmt"
+	"github.com/paracrawl/giashard"
 	"log"
 	"os"
-	"github.com/paracrawl/giashard"
+	"strings"
 )
 
 var outdir string
+var dirslist string
 var shards uint
 var batchsize int64
 var fileslist string
@@ -20,22 +22,55 @@ var schema = []string{"url", "mime", "plain_text"}
 
 func init() {
 	flag.StringVar(&outdir, "o", ".", "Output location")
+	flag.StringVar(&dirslist, "l", "", "Input file listing all input directories")
 	flag.StringVar(&fileslist, "f", "plain_text,url,mime", "Files to shard, separated by commas")
 	flag.UintVar(&shards, "n", 8, "Number of shards (2^n)")
 	flag.Int64Var(&batchsize, "b", 100, "Batch size in MB")
 	flag.StringVar(&domainList, "d", "", "Additional public suffix entries")
 	flag.Usage = func() {
-		fmt.Fprintf(flag.CommandLine.Output(), "Usage: %s [flags] input directories\n", os.Args[0])
+		_, err := fmt.Fprintf(flag.CommandLine.Output(), "Usage: %s [flags] input directories\n", os.Args[0])
+		if err != nil {
+			return
+		}
 		flag.PrintDefaults()
-		fmt.Fprintf(flag.CommandLine.Output(),
-`Shards together the directories give on input. They are assumed to be in the
+		_, err = fmt.Fprintf(flag.CommandLine.Output(),
+			`Shards together the directories given on input. They are assumed to be in the
 standard Paracrawl column storage format. The output is a tree of directories
 of the form: outdir/shard/batch where shard is computed as a hash of the
 significant part of the hostname in a url and batch is approximately fixed size.
 `)
+		if err != nil {
+			return
+		}
 	}
 }
 
+func processfile(source string, schema []string, w *giashard.Shard, hostname string) {
+	log.Printf("Processing input: %v", source)
+	r, err := giashard.NewColumnReader(source, schema...)
+	if err != nil {
+		log.Printf("Error opening input reader: %v", err)
+		return
+	}
+
+	// provenance data - where is this from
+	provdata := []byte(fmt.Sprintf("%s:%s", hostname, source))
+	for row := range r.Rows() {
+		row["source"] = provdata
+		if err := w.WriteRow(row); err != nil {
+			if errors.Is(err, giashard.ShardError) { // not fatal
+				log.Print(err)
+				continue
+			}
+			log.Fatalf("Error writing row: %v", err)
+		}
+	}
+
+	err = r.Close()
+	if err != nil {
+		return
+	}
+}
 func main() {
 	log.SetFlags(log.Ldate | log.Ltime | log.Lshortfile)
 	flag.Parse()
@@ -50,40 +85,47 @@ func main() {
 		}
 	}
 
-	w, err := giashard.NewShard(outdir, shards, batchsize * 1024 * 1024, "url", append(schema, "source")...)
+	w, err := giashard.NewShard(outdir, shards, batchsize*1024*1024, "url", append(schema, "source")...)
 	if err != nil {
 		log.Fatalf("Error opening output shards: %v", err)
 	}
-	defer w.Close()
+	defer func(w *giashard.Shard) {
+		var err = w.Close()
+		if err != nil {
+
+		}
+	}(w)
 
 	hostname, err := os.Hostname()
 	if err != nil {
 		log.Fatalf("Error getting local hostname: %v", err)
 	}
 
-	for i:=0; i<flag.NArg(); i++ {
+	for i := 0; i < flag.NArg(); i++ {
 		source := flag.Arg(i)
+		processfile(source, schema, w, hostname)
+	}
 
-		log.Printf("Processing input: %v", source)
-		r, err := giashard.NewColumnReader(source, schema...)
+	if dirslist != "" {
+		file, err := os.Open(dirslist)
 		if err != nil {
-			log.Printf("Error opening input reader: %v", err)
-			continue
+			log.Fatal(err)
 		}
+		defer func(file *os.File) {
+			var err = file.Close()
+			if err != nil {
 
-		// provenance data - where is this from
-		provdata := []byte(fmt.Sprintf("%s:%s", hostname, source))
-		for row := range r.Rows() {
-			row["source"] = provdata
-			if err := w.WriteRow(row); err != nil {
-				if errors.Is(err, giashard.ShardError) { // not fatal
-					log.Print(err)
-					continue
-				}
-				log.Fatalf("Error writing row: %v", err)
 			}
+		}(file)
+
+		scanner := bufio.NewScanner(file)
+		for scanner.Scan() {
+			source := scanner.Text()
+			processfile(source, schema, w, hostname)
 		}
 
-		r.Close()
+		if err := scanner.Err(); err != nil {
+			log.Fatal(err)
+		}
 	}
 }

go.mod

@@ -0,0 +1,13 @@
+module github.com/paracrawl/giashard
+
+go 1.18
+
+require (
+	github.com/weppos/publicsuffix-go v0.15.0
+	gopkg.in/yaml.v2 v2.4.0
+)
+
+require (
+	golang.org/x/net v0.0.0-20200202094626-16171245cfb2 // indirect
+	golang.org/x/text v0.3.0 // indirect
+)