Merge pull request #1159 from unclejack/add_container_id_file_to_run

*Client: Add support for container ID files (a la pidfile)

commands.go

@@ -1311,6 +1311,18 @@ func (cli *DockerCli) CmdRun(args ...string) error {
 		return nil
 	}
 
+	var containerIDFile *os.File
+	if len(hostConfig.ContainerIDFile) > 0 {
+		if _, err := ioutil.ReadFile(hostConfig.ContainerIDFile); err == nil {
+			return fmt.Errorf("cid file found, make sure the other container isn't running or delete %s", hostConfig.ContainerIDFile)
+		}
+		containerIDFile, err = os.Create(hostConfig.ContainerIDFile)
+		if err != nil {
+			return fmt.Errorf("failed to create the container ID file: %s", err)
+		}
+		defer containerIDFile.Close()
+	}
+
 	//create the container
 	body, statusCode, err := cli.call("POST", "/containers/create", config)
 	//if image not found try to pull it
@@ -1341,6 +1353,11 @@ func (cli *DockerCli) CmdRun(args ...string) error {
 	for _, warning := range runResult.Warnings {
 		fmt.Fprintf(cli.err, "WARNING: %s\n", warning)
 	}
+	if len(hostConfig.ContainerIDFile) > 0 {
+		if _, err = containerIDFile.WriteString(runResult.ID); err != nil {
+			return fmt.Errorf("failed to write the container ID to the file: %s", err)
+		}
+	}
 
 	//start the container
 	if _, _, err = cli.call("POST", "/containers/"+runResult.ID+"/start", hostConfig); err != nil {

container.go

@@ -81,6 +81,7 @@ type Config struct {
 
 type HostConfig struct {
 	Binds           []string
+	ContainerIDFile string
 }
 
 type BindMap struct {
@@ -103,6 +104,7 @@ func ParseRun(args []string, capabilities *Capabilities) (*Config, *HostConfig,
 	flStdin := cmd.Bool("i", false, "Keep stdin open even if not attached")
 	flTty := cmd.Bool("t", false, "Allocate a pseudo-tty")
 	flMemory := cmd.Int64("m", 0, "Memory limit (in bytes)")
+	flContainerIDFile := cmd.String("cidfile", "", "Write the container ID to the file")
 
 	if capabilities != nil && *flMemory > 0 && !capabilities.MemoryLimit {
 		//fmt.Fprintf(stdout, "WARNING: Your kernel does not support memory limit capabilities. Limitation discarded.\n")
@@ -191,6 +193,7 @@ func ParseRun(args []string, capabilities *Capabilities) (*Config, *HostConfig,
 	}
 	hostConfig := &HostConfig{
 		Binds:           binds,
+		ContainerIDFile: *flContainerIDFile,
 	}
 
 	if capabilities != nil && *flMemory > 0 && !capabilities.SwapLimit {

docs/sources/commandline/command/run.rst

@@ -14,6 +14,7 @@
 
       -a=map[]: Attach to stdin, stdout or stderr.
       -c=0: CPU shares (relative weight)
+      -cidfile="": Write the container ID to the file
       -d=false: Detached mode: leave the container running in the background
       -e=[]: Set environment variables
       -h="": Container host name
@@ -26,3 +27,13 @@
       -v=[]: Create a bind mount with: [host-dir]:[container-dir]:[rw|ro]. If "host-dir" is missing, then docker creates a new volume.
       -volumes-from="": Mount all volumes from the given container.
       -entrypoint="": Overwrite the default entrypoint set by the image.
+
+
+Examples
+--------
+
+.. code-block:: bash
+
+    docker run -cidfile /tmp/docker_test.cid ubuntu echo "test"
+
+| This will create a container and print "test" to the console. The cidfile flag makes docker attempt to create a new file and write the container ID to it. If the file exists already, docker will return an error. Docker will close this file when docker run exits.