Fix script invocation to work with post-2023 versions of util-linux.

agent/session/shell/shell_unix.go

@@ -344,16 +344,23 @@ func (p *ShellPlugin) generateLogData(log log.T, config agentContracts.Configura
 	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Minute)
 	defer cancel()
 
-	cmdWithFlag := exec.CommandContext(ctx, startRecordSessionCmd, p.logger.logFilePath, scriptFlag, loggerCmd)
+	// Invoke script with options before the logfile argument. util-linux >= 2.39 rejects
+	// positional arguments after the logfile (ec96a89, "script: abort if unused arguments
+	// are given", Nov 2022). The old forms "script <file> -c <cmd>" and
+	// "script <file> cmd args" both fail on util-linux >= 2.39 / >= 2.42 respectively.
+	// Using "-c" with the logfile last is valid on all util-linux versions and on BSD script.
+	// See: https://github.com/aws/amazon-ssm-agent/issues/667
+	cmdWithFlag := exec.CommandContext(ctx, startRecordSessionCmd, scriptFlag, loggerCmd, p.logger.logFilePath)
 	cmdWithFlag.Stderr = &flagStderr
 	flagErr := cmdWithFlag.Run()
 	if flagErr != nil {
 		log.Debugf("Failed to generate transcript with -c flag: %v: %s", flagErr, flagStderr.String())
 
 		var noFlagStderr bytes.Buffer
 
-		// some versions of "script" does not take a -c flag when passing in commands.
-		cmdWithoutFlag := exec.CommandContext(ctx, startRecordSessionCmd, p.logger.logFilePath, catCmd, p.logger.ipcFilePath)
+		// Fallback for script implementations that predate -c support.
+		// Arguments are ordered to satisfy util-linux >= 2.39 strict parsing.
+		cmdWithoutFlag := exec.CommandContext(ctx, startRecordSessionCmd, catCmd, p.logger.ipcFilePath, p.logger.logFilePath)
 		cmdWithoutFlag.Stderr = &noFlagStderr
 		noFlagErr := cmdWithoutFlag.Run()
 		if noFlagErr != nil {

agent/session/shell/shell_unix_test.go

@@ -514,6 +514,41 @@ func (suite *ShellTestSuite) TestProcessStreamMessage() {
 	assert.Equal(suite.T(), "testPayload", string(stdinFileContent))
 }
 
+// TestGenerateLogData verifies that generateLogData invokes script(1) with the correct
+// argument order for util-linux >= 2.39. Prior to the fix, the logfile was passed as
+// the first positional argument ("script <file> -c <cmd>"), which util-linux >= 2.39
+// rejects with "unexpected number of arguments". The correct form is
+// "script -q -c <cmd> <file>".
+//
+// This test requires the `script` binary to be present on the system (util-linux or BSD).
+func (suite *ShellTestSuite) TestGenerateLogData() {
+	ipcFile, err := os.CreateTemp("", "ipc-*.log")
+	assert.Nil(suite.T(), err)
+	defer os.Remove(ipcFile.Name())
+
+	logFile, err := os.CreateTemp("", "transcript-*.log")
+	assert.Nil(suite.T(), err)
+	logFile.Close()
+	defer os.Remove(logFile.Name())
+
+	testContent := "hello from generateLogData test"
+	_, err = ipcFile.WriteString(testContent)
+	assert.Nil(suite.T(), err)
+	ipcFile.Close()
+
+	suite.plugin.logger = logger{
+		ipcFilePath: ipcFile.Name(),
+		logFilePath: logFile.Name(),
+	}
+
+	err = suite.plugin.generateLogData(suite.mockLog, contracts.Configuration{})
+	assert.Nil(suite.T(), err, "generateLogData should succeed; check that script(1) is installed and util-linux argument order is correct")
+
+	transcript, err := os.ReadFile(logFile.Name())
+	assert.Nil(suite.T(), err)
+	assert.Contains(suite.T(), string(transcript), testContent, "transcript file should contain the ipc file content")
+}
+
 // getAgentMessage constructs and returns AgentMessage with given sequenceNumber, messageType & payload
 func getAgentMessage(payloadType uint32, payload []byte) *mgsContracts.AgentMessage {
 	messageUUID, _ := uuid.Parse(messageId)