go-delve/delve · error

could not create stderr file: %v

Error message

could not create stderr file: %v

What it means

Delve's DAP server failed to create a temporary file to which the debuggee's stderr (or stdout) would be redirected when launching the process. This is a local filesystem error wrapped with context; the underlying OS error (permissions, missing directory, too many open files) is embedded in the message.

Source

Thrown at service/dap/server.go:1459

				return f
			}

			return dflt
		}
		defer func() {
			for _, f := range toclose {
				f.Close()
			}
		}()

		cmd.Stdout = create(stdoutTo, os.Stdout)
		if err != nil {
			return nil, nil, nil, fmt.Errorf("could not create stdout file: %v", err)
		}

		cmd.Stderr = create(stderrTo, os.Stderr)
		if err != nil {
			return nil, nil, nil, fmt.Errorf("could not create stderr file: %v", err)
		}
	}

	if err = cmd.Start(); err != nil {
		return nil, nil, nil, err
	}

	s.noDebugProcess = &process{Cmd: cmd, exited: make(chan struct{})}
	return cmd, stdoutReader, stderrReader, nil
}

// stopNoDebugProcess is called from Stop (main goroutine) and
// onDisconnectRequest (run goroutine) and requires holding mu lock.
func (s *Session) stopNoDebugProcess() {
	if s.noDebugProcess == nil {
		s.disconnected = true
		// We already handled termination or there was never a process
		return

View on GitHub (pinned to a23773e6c3)

Solutions

1. Check the directory used for the redirect/temp file exists and is writable by the user running DAP
2. Free disk space or raise ulimit -n if 'too many open files' is reported
3. Run the editor/DAP client in an environment with a writable TMPDIR
4. Read the wrapped OS error in the message to identify the exact filesystem cause

Example fix

// before: launching with stderr redirected to a non-writable path
{"request":"launch","console":"integratedTerminal","outputPath":"/proc/mydir/log"}
// after: use a writable location
{"request":"launch","console":"integratedTerminal","outputPath":"/tmp/dlv-log"}

if st, err := os.Stat(outputDir); err != nil || !st.IsDir() { return fmt.Errorf("output dir not writable: %v", outputDir) }
if f, err := os.CreateTemp(outputDir, "dlv-stderr-*"); err != nil { return err } else { f.Close() }

if err := startDAPLaunch(cfg); err != nil { if strings.Contains(err.Error(), "could not create stderr file") { /* fix outputPath/TMPDIR */ } return err }

When it happens

Trigger: An onLaunchRequest (or onAttachRequest with launch semantics) where the launch configuration requests output redirection (e.g. console internals / outputPath handling) and os.CreateFile-style creation of the stderr target file fails with an OS error.

Common situations: Read-only or non-existent output directory, disk full, restrictive file permissions/umask, or hitting the open-file limit when many sessions create temp files.

Related errors

• not an executable file
• another launch request is in progress
• could not open stdin file: %v
• could not create stdout file: %v
• could not launch process: %s

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/6a9768503f93aacf. Report an issue: GitHub.