wavetermdev/waveterm · error

reading stdin: %w

Error message

reading stdin: %w

What it means

With --stdin, debugTermRun reads all of standard input via io.ReadAll(WrappedStdin) before parsing it as terminal data. Any read failure (broken pipe, I/O error on the wrapped reader) is wrapped as 'reading stdin'.

Source

Thrown at cmd/wsh/cmd/wshcmd-debugterm.go:62

	rootCmd.AddCommand(debugTermCmd)
	debugTermCmd.Flags().Int64Var(&debugTermSize, "size", 1000, "number of terminal bytes to read")
	debugTermCmd.Flags().StringVar(&debugTermMode, "mode", DebugTermModeHex, "output mode: hex or decode")
	debugTermCmd.Flags().BoolVar(&debugTermStdin, "stdin", false, "read input from stdin instead of rpc call")
	debugTermCmd.Flags().StringVar(&debugTermInput, "input", "", "read input from file instead of rpc call")
}

func debugTermRun(cmd *cobra.Command, args []string) (rtnErr error) {
	defer func() {
		sendActivity("debugterm", rtnErr == nil)
	}()
	mode, err := getDebugTermMode()
	if err != nil {
		return err
	}
	if debugTermStdin {
		stdinData, err := io.ReadAll(WrappedStdin)
		if err != nil {
			return fmt.Errorf("reading stdin: %w", err)
		}
		termData, err := parseDebugTermStdinData(stdinData)
		if err != nil {
			return err
		}
		if mode == DebugTermModeDecode {
			WriteStdout("%s", formatDebugTermDecode(termData))
		} else {
			WriteStdout("%s", formatDebugTermHex(termData))
		}
		return nil
	}
	if debugTermInput != "" {
		fileData, err := os.ReadFile(debugTermInput)
		if err != nil {
			return fmt.Errorf("reading input file: %w", err)
		}
		termData, err := parseDebugTermStdinData(fileData)

View on GitHub (pinned to a4447c1563)

Solutions

1. Check the upstream command in the pipe completed successfully before debugterm
2. Re-run writing the data to a file and use --input instead of --stdin
3. Avoid intermediate filters (grep/sed) that may close the pipe early — use cat
4. Test with a small known-good file: cat data.bin | wsh debugterm --stdin

Example fix

// before
flaky-producer | wsh debugterm --stdin --decode
// after
flaky-producer > /tmp/capture.bin && wsh debugterm --input /tmp/capture.bin --decode

// verify the pipe producer succeeded and data is non-empty first
producer && [ -s capture.bin ] && cat capture.bin | wsh debugterm --stdin

stdinData, err := io.ReadAll(WrappedStdin)
if err != nil {
	return fmt.Errorf("reading stdin: %w — check the upstream pipe producer exited cleanly", err)
}

When it happens

Trigger: Piping into `wsh debugterm --stdin` when the upstream writer fails or closes the pipe abruptly; the wrapped stdin reader (pty-aware) hits an OS-level I/O error.

Common situations: A producer command crashed mid-pipe (e.g. `producer | wsh debugterm --stdin`); piping from a device that errors; attempting to feed binary data through a layer that mangles/closes the stream.

Related errors

• reading from stdin: %w
• failed to read JWT token from stdin: %w
• stdin (-) can only be used once
• reading input file: %w
• reading terminal output: %w

AI-assisted analysis of wavetermdev/waveterm@a4447c1563 (2026-09-01). Data as JSON: /api/errors/3a851ddbf5905be4. Report an issue: GitHub.