gcsbuf/cmd/gcscat/main.go

package main

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"os"
	"sync"
	"time"

	"cloud.google.com/go/storage"
	buf "github.com/imjasonh/gcsbuf"
)

func main() {
	if len(os.Args) != 3 {
		fmt.Fprintf(os.Stderr, "usage: gcscat <bucket> <object>\n")
		os.Exit(1)
	}
	bucket, object := os.Args[1], os.Args[2]

	ctx := context.Background()
	client, err := storage.NewClient(ctx)
	if err != nil {
		slog.Error("creating storage client", "err", err)
		os.Exit(1)
	}
	defer client.Close()

	onOp := buf.OnOp(func(op string, d time.Duration, err error) {
		if err != nil {
			slog.Error("gcs", "op", op, "dur", d, "err", err)
		} else {
			slog.Info("gcs", "op", op, "dur", d)
		}
	})

	w := buf.NewWriter(ctx, buf.WriterOptions{
		Client: client,
		Bucket: bucket,
		Object: object,
		OnOp:   onOp,
	})

	r := buf.NewReader(ctx, buf.ReaderOptions{
		Client: client,
		Bucket: bucket,
		Object: object,
		OnOp:   onOp,
	})

	// Read concurrently, printing to stdout.
	var wg sync.WaitGroup
	wg.Go(func() {
		if _, err := io.Copy(os.Stdout, r); err != nil {
			slog.Error("read", "err", err)
		}
	})

	// Write stdin to GCS.
	if _, err := io.Copy(w, os.Stdin); err != nil {
		slog.Error("write", "err", err)
		os.Exit(1)
	}
	if err := w.Close(); err != nil {
		slog.Error("close writer", "err", err)
		os.Exit(1)
	}

	wg.Wait()
}