added stdin support for topos (#1621)

* added stdin support for topos

* lazy to use act, testing in gh actions

* create clab temp dir before reading from stdin

clab/clab.go

@@ -126,13 +126,24 @@ func WithKeepMgmtNet() ClabOption {
 
 func WithTopoPath(path, varsFile string) ClabOption {
 	return func(c *CLab) error {
-		if path == "" {
+		var file string
+		var err error
+
+		switch path {
+		case "-", "stdin":
+			file, err = c.readFromStdin()
+			if err != nil {
+				return err
+			}
+
+		case "":
 			return fmt.Errorf("provide a path to the clab topology file")
-		}
 
-		file, err := findTopoFileByPath(path)
-		if err != nil {
-			return err
+		default:
+			file, err = findTopoFileByPath(path)
+			if err != nil {
+				return err
+			}
 		}
 
 		if err := c.GetTopology(file, varsFile); err != nil {
@@ -184,6 +195,25 @@ func findTopoFileByPath(path string) (string, error) {
 	return file, nil
 }
 
+// readFromStdin reads the topology file from stdin
+// creates a temp file with topology contents
+// and returns a path to the temp file.
+func (c *CLab) readFromStdin() (string, error) {
+	c.TopoPaths.CreateTmpDir()
+
+	tmpFile, err := os.CreateTemp(c.TopoPaths.ClabTmpDir(), "topo-*.clab.yml")
+	if err != nil {
+		return "", err
+	}
+
+	_, err = tmpFile.ReadFrom(os.Stdin)
+	if err != nil {
+		return "", err
+	}
+
+	return tmpFile.Name(), nil
+}
+
 // WithNodeFilter option sets a filter for nodes to be deployed.
 // A filter is a list of node names to be deployed,
 // names are provided exactly as they are listed in the topology file.

clab/config.go

@@ -268,8 +268,7 @@ func (c *CLab) processStartupConfig(nodeCfg *types.NodeConfig) error {
 
 	if isEmbeddedConfig || isDownloadableConfig {
 		// both embedded and downloadable configs are require clab tmp dir to be created
-		tmpLoc := c.TopoPaths.ClabTmpDir()
-		utils.CreateDirectory(tmpLoc, 0755)
+		c.TopoPaths.CreateTmpDir()
 
 		switch {
 		case isEmbeddedConfig:

docs/cmd/deploy.md

@@ -22,6 +22,8 @@ When the topology file flag is omitted, containerlab will try to find the matchi
 
 If more than one file is found for directory-based path or when the flag is omitted entirely, containerlab will fail with an error.
 
+It is possible to read the topology file from stdin by passing `-` as a value to the `--topo` flag. See [examples](#deploy-a-lab-from-a-remote-url-with-curl) for more details.
+
 #### name
 
 With the global `--name | -n` flag a user sets a lab name. This value will override the lab name value passed in the topology definition file.
@@ -140,3 +142,10 @@ containerlab deploy
 ```bash
 clab dep -t mylab.clab.yml
 ```
+
+#### Deploy a lab from a remote URL with curl
+
+```bash
+curl -s https://gist.githubusercontent.com/hellt/9baa28d7e3cb8290ade1e1be38a8d12b/raw/03067e242d44c9bbe38afa81131e46bab1fa0c42/test.clab.yml | \
+    sudo containerlab deploy -t -
+```

tests/01-smoke/13-stdin-lab.robot

@@ -0,0 +1,31 @@
+*** Settings ***
+Library             OperatingSystem
+Library             String
+Library             Process
+Resource            ../common.robot
+
+Suite Teardown      Run Keyword    Teardown
+
+
+*** Variables ***
+${lab-url}      https://gist.githubusercontent.com/hellt/9baa28d7e3cb8290ade1e1be38a8d12b/raw/03067e242d44c9bbe38afa81131e46bab1fa0c42/test.clab.yml
+
+
+*** Test Cases ***
+Deploy remote lab
+    ${rc}    ${output} =    Run And Return Rc And Output
+    ...    sudo curl -s ${lab-url} | sudo ${CLAB_BIN} --runtime ${runtime} deploy -c -t -
+    Log    ${output}
+    Should Be Equal As Integers    ${rc}    0
+
+Ensure inspect works
+    ${rc}    ${output} =    Run And Return Rc And Output
+    ...    sudo ${CLAB_BIN} --runtime ${runtime} inspect --all
+    Log    ${output}
+    Should Be Equal As Integers    ${rc}    0
+
+
+*** Keywords ***
+Teardown
+    # destroy all labs
+    Run    sudo ${CLAB_BIN} --runtime ${runtime} destroy -c -a

types/topo_paths.go

@@ -165,6 +165,11 @@ func (*TopoPaths) ClabTmpDir() string {
 	return clabTmpDir
 }
 
+// CreateTmpDir creates a clab temp directory.
+func (t *TopoPaths) CreateTmpDir() {
+	utils.CreateDirectory(t.ClabTmpDir(), 0755)
+}
+
 // StartupConfigDownloadFileAbsPath returns the absolute path to the startup-config file
 // when it is downloaded from a remote location to the clab temp directory.
 func (t *TopoPaths) StartupConfigDownloadFileAbsPath(node, postfix string) string {