mc/cmd-cat.go

/*
 * Minio Client, (C) 2015 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package main

import (
	"fmt"
	"io"
	"os"
	"syscall"

	"github.com/minio/cli"
	"github.com/minio/mc/pkg/console"
	"github.com/minio/minio/pkg/iodine"
)

// Help message.
var catCmd = cli.Command{
	Name:   "cat",
	Usage:  "Display contents of a file",
	Action: runCatCmd,
	CustomHelpTemplate: `NAME:
   mc {{.Name}} - {{.Usage}}

USAGE:
   mc {{.Name}}{{if .Flags}} [ARGS...]{{end}} SOURCE [SOURCE...] {{if .Description}}

DESCRIPTION:
   {{.Description}}{{end}}{{if .Flags}}

FLAGS:
   {{range .Flags}}{{.}}
   {{end}}{{ end }}

EXAMPLES:
   1. Concantenate an object from Amazon S3 object storage to mplayer standard input.
      $ mc {{.Name}} https://s3.amazonaws.com/ferenginar/klingon_opera_aktuh_maylotah.ogg | mplayer -

   2. Concantenate a file from local filesystem to standard output.
      $ mc {{.Name}} khitomer-accords.txt

   3. Concantenate multiple files from local filesystem to standard output.
      $ mc {{.Name}} *.txt > newfile.txt

   4. Concatenate a non english file name from Amazon S3 object storage.
      $ mc {{.Name}} s3:andoria/本語 > /tmp/本語

`,
}

func runCatCmd(ctx *cli.Context) {
	if !ctx.Args().Present() || ctx.Args().First() == "help" {
		cli.ShowCommandHelpAndExit(ctx, "cat", 1) // last argument is exit code
	}
	if !isMcConfigExist() {
		console.Fatals(ErrorMessage{
			Message: "Please run \"mc config generate\"",
			Error:   iodine.New(errNotConfigured{}, nil),
		})
	}
	config, err := getMcConfig()
	if err != nil {
		console.Fatals(ErrorMessage{
			Message: fmt.Sprintf("Unable to read config file ‘%s’", mustGetMcConfigPath()),
			Error:   iodine.New(err, nil),
		})
	}
	// Convert arguments to URLs: expand alias, fix format...
	for _, arg := range ctx.Args() {
		sourceURL, err := getExpandedURL(arg, config.Aliases)
		if err != nil {
			switch e := iodine.ToError(err).(type) {
			case errUnsupportedScheme:
				console.Fatals(ErrorMessage{
					Message: fmt.Sprintf("Unknown type of URL ‘%s’", e.url),
					Error:   iodine.New(e, nil),
				})
			default:
				console.Fatals(ErrorMessage{
					Message: fmt.Sprintf("Unable to parse argument ‘%s’", arg),
					Error:   iodine.New(err, nil),
				})
			}
		}
		errorMsg, err := doCatCmd(sourceURL)
		if err != nil {
			console.Fatals(ErrorMessage{
				Message: errorMsg,
				Error:   iodine.New(err, nil),
			})
		}
	}
}

func doCatCmd(sourceURL string) (string, error) {
	sourceClnt, err := source2Client(sourceURL)
	if err != nil {
		return "Unable to create client: " + sourceURL, iodine.New(err, nil)
	}
	reader, size, err := sourceClnt.GetObject(0, 0)
	if err != nil {
		return "Unable to retrieve file: " + sourceURL, iodine.New(err, nil)
	}
	defer reader.Close()
	_, err = io.CopyN(os.Stdout, reader, int64(size))
	if err != nil {
		switch e := iodine.ToError(err).(type) {
		case *os.PathError:
			if e.Err == syscall.EPIPE {
				// stdout closed by the user. Gracefully exit.
				return "", nil
			}
			return "Writing data to stdout failed, unexpected problem.. please report this error", iodine.New(err, nil)
		default:
			return "Reading data from source failed: " + sourceURL, iodine.New(err, nil)
		}
	}
	return "", nil
}