Modified `docker export` to allow an --output flag

Copied code from CmdSave into CmdExport. This should work, not an expert in the API calls being made. But it does make more sense to have a consistent export/save flag.

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

checkpoint before edits on the export functions

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

Added an --output flag to docker export and created tests.

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

White space cleanup.

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

Docker-DCO-1.1-Signed-off-by: Joseph Kern <jkern@semafour.net> (github: jfrazelle)

checkpoint before edits on the export functions

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

White space cleanup.

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

Added text to reflect a new output option for the export command.

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

Whitespace clean up

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

Added man page documentation for the new --output flag in export

Signed-off-by: Joseph Kern <joseph.a.kern@gmail.com>

api/client/commands.go

@@ -1872,14 +1872,40 @@ func (cli *DockerCli) CmdEvents(args ...string) error {
 }
 
 func (cli *DockerCli) CmdExport(args ...string) error {
-	cmd := cli.Subcmd("export", "CONTAINER", "Export the contents of a filesystem as a tar archive to STDOUT", true)
+	cmd := cli.Subcmd("export", "CONTAINER", "Export a filesystem as a tar archive (streamed to STDOUT by default)", true)
+	outfile := cmd.String([]string{"o", "-output"}, "", "Write to a file, instead of STDOUT")
 	cmd.Require(flag.Exact, 1)
 
 	utils.ParseFlags(cmd, args, true)
 
-	if err := cli.stream("GET", "/containers/"+cmd.Arg(0)+"/export", nil, cli.out, nil); err != nil {
-		return err
+	var (
+		output io.Writer = cli.out
+		err    error
+	)
+	if *outfile != "" {
+		output, err = os.Create(*outfile)
+		if err != nil {
+			return err
+		}
+	} else if cli.isTerminalOut {
+		return errors.New("Cowardly refusing to save to a terminal. Use the -o flag or redirect.")
+	}
+
+	if len(cmd.Args()) == 1 {
+		image := cmd.Arg(0)
+		if err := cli.stream("GET", "/containers/"+image+"/export", nil, output, nil); err != nil {
+			return err
+		}
+	} else {
+		v := url.Values{}
+		for _, arg := range cmd.Args() {
+			v.Add("names", arg)
+		}
+		if err := cli.stream("GET", "/containers/get?"+v.Encode(), nil, output, nil); err != nil {
+			return err
+		}
 	}
+
 	return nil
 }
 

docs/man/docker-export.1.md

@@ -14,17 +14,24 @@ Export the contents of a container's filesystem using the full or shortened
 container ID or container name. The output is exported to STDOUT and can be
 redirected to a tar file.
 
+Stream to a file instead of STDOUT by using **-o**.
+
 # OPTIONS
 **--help**
   Print usage statement
+**-o**, **--output**=""
+   Write to a file, instead of STDOUT
 
 # EXAMPLES
 Export the contents of the container called angry_bell to a tar file
-called test.tar:
+called angry_bell.tar:
 
-    # docker export angry_bell > test.tar
-    # ls *.tar
-    test.tar
+    # docker export angry_bell > angry_bell.tar
+    # docker export --output=angry_bell-latest.tar angry_bell
+    # ls -sh angry_bell.tar
+    321M angry_bell.tar
+    # ls -sh angry_bell-latest.tar
+    321M angry_bell-latest.tar
 
 # See also
 **docker-import(1)** to create an empty filesystem image
@@ -34,3 +41,4 @@ and import the contents of the tarball into it, then optionally tag it.
 April 2014, Originally compiled by William Henry (whenry at redhat dot com)
 based on docker.com source material and internal work.
 June 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
+Janurary 2015, updated by Joseph Kern (josephakern at gmail dot com)

docs/sources/reference/commandline/cli.md

@@ -1066,14 +1066,22 @@ This will create a new Bash session in the container `ubuntu_bash`.
 
 ## export
 
-    Usage: docker export CONTAINER
+    Usage: docker export [OPTIONS] CONTAINER
 
-    Export the contents of a filesystem as a tar archive to STDOUT
+    Export the contents of a filesystem to a tar archive (streamed to STDOUT by default)
 
-For example:
+      -o, --output=""    Write to a file, instead of STDOUT
+
+      Produces a tarred repository to the standard output stream.
+
+   For example:
 
     $ sudo docker export red_panda > latest.tar
 
+   Or
+
+    $ sudo docker export --output="latest.tar" red_panda
+
 > **Note:**
 > `docker export` does not export the contents of volumes associated with the
 > container. If a volume is mounted on top of an existing directory in the

integration-cli/docker_cli_export_import_test.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"fmt"
+	"os"
 	"os/exec"
 	"strings"
 	"testing"
@@ -47,3 +49,49 @@ func TestExportContainerAndImportImage(t *testing.T) {
 	logDone("export - export a container")
 	logDone("import - import an image")
 }
+
+// Used to test output flag in the export command
+func TestExportContainerWithOutputAndImportImage(t *testing.T) {
+	runCmd := exec.Command(dockerBinary, "run", "-d", "busybox", "true")
+	out, _, err := runCommandWithOutput(runCmd)
+	if err != nil {
+		t.Fatal("failed to create a container", out, err)
+	}
+
+	cleanedContainerID := stripTrailingCharacters(out)
+
+	inspectCmd := exec.Command(dockerBinary, "inspect", cleanedContainerID)
+	out, _, err = runCommandWithOutput(inspectCmd)
+	if err != nil {
+		t.Fatalf("output should've been a container id: %s %s ", cleanedContainerID, err)
+	}
+
+	exportCmdTemplate := `%v export --output=/tmp/testexp.tar %v`
+	exportCmdFinal := fmt.Sprintf(exportCmdTemplate, dockerBinary, cleanedContainerID)
+	exportCmd := exec.Command(exportCmdFinal)
+	if out, _, err = runCommandWithOutput(exportCmd); err != nil {
+		t.Fatalf("failed to export container: %s, %v", out, err)
+	}
+
+	importCmdFinal := `cat /tmp/testexp.tar | docker import - repo/testexp:v1`
+	importCmd := exec.Command(importCmdFinal)
+	out, _, err = runCommandWithOutput(importCmd)
+	if err != nil {
+		t.Fatalf("failed to import image: %s, %v", out, err)
+	}
+
+	cleanedImageID := stripTrailingCharacters(out)
+
+	inspectCmd = exec.Command(dockerBinary, "inspect", cleanedImageID)
+	if out, _, err = runCommandWithOutput(inspectCmd); err != nil {
+		t.Fatalf("output should've been an image id: %s, %v", out, err)
+	}
+
+	deleteContainer(cleanedContainerID)
+	deleteImages("repo/testexp:v1")
+
+	os.Remove("/tmp/testexp.tar")
+
+	logDone("export - export a container with output flag")
+	logDone("import - import an image with output flag")
+}