dbt-labs/dbt-core · error

failed to write show result to stdout

Error message

failed to write show result to stdout

What it means

This panic comes from an `.expect()` on `Stdout::write_all` inside the TUI tracing layer's `handle_show_result`. It fires when dbt fails to write a `show` result (in quiet mode: raw content, no title header) to stdout. The most common underlying cause is a broken pipe — the downstream consumer (e.g. `head`, a pager, or a closed terminal) has stopped reading or the pipe is closed, so the write fails and the panic message surfaces instead of the data.

Source

Thrown at crates/dbt-common/src/tracing/layers/tui_layer.rs:1442

            let mut stdout = io::stdout().lock();

            stdout
                .write_all(format!("{}\n", show_data.content).as_bytes())
                .expect("failed to write show data to stdout");
        });
    }

    fn handle_show_result(&self, show_result: &ShowResult) {
        self.write_suspended(|| {
            let mut stdout = io::stdout().lock();

            if self.show_options.is_empty() {
                // Quiet mode: suppress decorative title, emit raw content only.
                // Mirrors dbt-core's ShowNode quiet=True behaviour where the
                // "Previewing node 'X':" header is dropped but the data is kept.
                stdout
                    .write_all(format!("{}\n", show_result.content).as_bytes())
                    .expect("failed to write show result to stdout");
            } else {
                let colored_title = BLUE.apply_to(&show_result.title);
                stdout
                    .write_all(format!("\n{}\n{}\n", colored_title, show_result.content).as_bytes())
                    .expect("failed to write show result to stdout");
            }
        });
    }

    fn handle_compiled_code_inline(&self, compiled_code: &CompiledCodeInline) {
        // Only show if any Progress*, Completed or All option is enabled
        let should_show = self.show_options.contains(&ShowOptions::Progress)
            || self.show_options.contains(&ShowOptions::ProgressRender)
            || self.show_options.contains(&ShowOptions::Completed)
            || self.show_options.contains(&ShowOptions::All);

        if !should_show {
            return;

View on GitHub (pinned to 0267ce9170)

Solutions

1. Avoid piping dbt output to commands that exit early (e.g. `head`); redirect to a file instead: `dbt show ... > out.txt`.
2. Set RUST_BACKTRACE=1 and check the panic source; if it is broken-pipe, confirm the downstream reader consumes all output.
3. Restore a valid stdout — run dbt in a live terminal or with stdout attached to a file, not a closed descriptor.
4. If the process must survive closed pipes, invoke dbt with output to stderr only (quiet/suppress options) so the show-result write path is not hit.
5. Upgrade dbt — newer versions may replace `.expect` with graceful SIGPIPE handling.

Example fix

// before
stdout
    .write_all(format!("{}\n", show_result.content).as_bytes())
    .expect("failed to write show result to stdout");
// after
let _ = stdout
    .write_all(format!("{}\n", show_result.content).as_bytes());
stdout.flush().ok();

// bash: ensure stdout is writable and no early-exiting pipe consumer
[ -w /dev/stdout ] && echo "stdout writable"

// from the library side: replace expect with error-tolerant write
if let Err(e) = stdout.write_all(bytes) {
    eprintln!("show result not written: {e}");
}

When it happens

Trigger: A dbt `show` invocation whose output is piped into a command that exits early (e.g. `dbt show ... | head -5`), or whose stdout is a closed/invalid file descriptor, causing `write_all` on the locked stdout to return Err and the `.expect` to panic.

Common situations: Developers piping `dbt show` output into `head`, `less -F`, or a script that exits before reading all output; running dbt in CI with stdout redirected to a closed stream; terminal emulators closing the PTY mid-run.

Related errors

• failed to write compiled code to stdout
• failed to write to stdout
• failed to write header to stdout
• failed to write show data to stdout
• Schema not found for canonical FQN: {}

AI-assisted analysis of dbt-labs/dbt-core@0267ce9170 (2026-09-07). Data as JSON: /api/errors/c8dd55a43f480404. Report an issue: GitHub.