Write output to stdout

Cargo.toml

@@ -17,6 +17,7 @@ duration-string = { version = "0.5.3", features = ["serde"] }
 derive_builder = "0.20.2"
 dirs = "6.0.0"
 futures = "0.3.32"
+rustix = { version = "1.1.4", features = ["stdio"] }
 serde = "1.0.228"
 termcfg = { version = "0.2.0", features = ["crossterm_0_29_0"] }
 tokio = { version = "1.49.0", features = ["full"] }

README.md

@@ -111,8 +111,14 @@ cargo install jnv
 
 ```bash
 cat data.json | jnv
+
 # or
 jnv data.json
+
+# or write current result to stdout on exit (UNIX only)
+cat data.json | jnv --write-to-stdout | some-command
+# and also output to file
+cat data.json | jnv -- --write-to-stdout > result.json
 ```
 
 ## Keymap
@@ -180,6 +186,7 @@ Arguments:
 Options:
   -c, --config <CONFIG_FILE>             Path to the configuration file.
       --default-filter <DEFAULT_FILTER>  Default jq filter to apply to the input data
+      --write-to-stdout                  Write the current JSON result to stdout when exiting
   -h, --help                             Print help (see more with '--help')
   -V, --version                          Print version
 ```
@@ -389,9 +396,9 @@ on_completion.down = ["Down", "Tab"]
 # Keybindings for JSON viewer operations
 [keybinds.on_json_viewer]
 # Move up in JSON viewer
-up = ["Up", "Ctrl+K"]
+up = ["Up", "Ctrl+K", "ScrollUp"]
 # Move down in JSON viewer
-down = ["Down", "Ctrl+J"]
+down = ["Down", "Ctrl+J", "ScrollDown"]
 # Move to the top of JSON viewer
 move_to_head = ["Ctrl+L"]
 # Move to the bottom of JSON viewer

src/main.rs

@@ -17,6 +17,8 @@ use editor::Editor;
 mod config;
 mod json;
 use json::JsonStreamProvider;
+mod stdout_redirect;
+use stdout_redirect::StdoutRedirect;
 mod processor;
 use processor::{
     init::ViewInitializer, monitor::ContextMonitor, spinner::SpinnerSpawner, Context, Processor,
@@ -70,6 +72,12 @@ pub struct Args {
         "
     )]
     default_filter: Option<String>,
+
+    #[arg(
+        long = "write-to-stdout",
+        help = "Write the current JSON result to stdout when exiting"
+    )]
+    write_to_stdout: bool,
 }
 
 /// Parses the input based on the provided arguments.
@@ -194,17 +202,31 @@ async fn main() -> anyhow::Result<()> {
         config.keybinds.on_editor.clone(),
     );
 
+    let mut stdout_redirect = StdoutRedirect::try_new_for_tui(args.write_to_stdout)?;
+
     // TODO: put all logics here.
-    prompt::run(
+    let maybe_output = prompt::run(
         item,
         config.reactivity_control,
         provider,
         editor,
         loading_suggestions_task,
         config.no_hint,
         config.keybinds,
+        args.write_to_stdout,
     )
-    .await?;
+    .await;
+
+    stdout_redirect.restore()?;
+    let maybe_output = maybe_output?;
+
+    if let Some(output) = maybe_output {
+        let mut stdout = io::stdout();
+        stdout.write_all(output.as_bytes())?;
+        if !output.ends_with('\n') {
+            stdout.write_all(b"\n")?;
+        }
+    }
 
     Ok(())
 }

src/prompt.rs

@@ -70,7 +70,7 @@
                     }),
                     ..Default::default()
                 },
                 ..Default::default()
             },
             Err(e) => text::State {
                 text: Text::from(format!("Failed to copy to clipboard: {e}")),
@@ -81,7 +81,7 @@
                     }),
                     ..Default::default()
                 },
                 ..Default::default()
             },
         },
         // arboard fails (in the specific environment like linux?) on Clipboard::new()
@@ -96,7 +96,7 @@
                 }),
                 ..Default::default()
             },
             ..Default::default()
         },
     }
 }
@@ -123,7 +123,8 @@
     loading_suggestions_task: JoinHandle<anyhow::Result<()>>,
     no_hint: bool,
     keybinds: Keybinds,
-) -> anyhow::Result<()> {
+    write_to_stdout: bool,
+) -> anyhow::Result<Option<String>> {
     enable_raw_mode()?;
     execute!(io::stdout(), cursor::Hide)?;
 
@@ -243,7 +244,7 @@
                                                     }),
                                                     ..Default::default()
                                                 },
                                                 ..Default::default()
                                             }.create_pane(size.0, size.1),
                                         ),
                                     ]).render().await?;
@@ -274,7 +275,7 @@
                                                             }),
                                                             ..Default::default()
                                                         },
                                                         ..Default::default()
                                                     }.create_pane(size.0, size.1)),
                                             ]).render().await?;
                                         }
@@ -385,11 +386,11 @@
         })
     };
 
+    let shared_visualizer = Arc::new(Mutex::new(initializing.await?));
     let processor_task: JoinHandle<anyhow::Result<()>> = {
         let shared_renderer = shared_renderer.clone();
         let shared_editor = shared_editor.clone();
-        let visualizer = initializing.await?;
-        let shared_visualizer = Arc::new(Mutex::new(visualizer));
+        let shared_visualizer = shared_visualizer.clone();
         tokio::spawn(async move {
             loop {
                 tokio::select! {
@@ -460,6 +461,13 @@
 
     main_task.await??;
 
+    let output = if write_to_stdout {
+        let visualizer = shared_visualizer.lock().await;
+        Some(visualizer.content_to_copy().await)
+    } else {
+        None
+    };
+
     loading_suggestions_task.abort();
     spinning.abort();
     query_debouncer.abort();
@@ -470,5 +478,5 @@
     execute!(io::stdout(), cursor::Show, DisableMouseCapture)?;
     disable_raw_mode()?;
 
-    Ok(())
+    Ok(output)
 }

src/stdout_redirect.rs

@@ -0,0 +1,89 @@
+use std::{
+    fs::File,
+    io::{self, IsTerminal},
+};
+
+use anyhow::anyhow;
+
+#[cfg(unix)]
+use rustix::{
+    io::dup,
+    stdio::{dup2_stdout, stdout},
+};
+#[cfg(unix)]
+use std::os::fd::OwnedFd;
+
+/// Redirects `stdout` to the controlling TTY while the TUI is running.
+///
+/// This is needed when `--write-to-stdout` is used with piped stdout, e.g.
+/// `cat data.json | jnv --write-to-stdout | pbcopy`.
+/// During interactive rendering, cursor controls and screen output must go to
+/// a terminal, not to the downstream pipe.
+///
+/// Unix flow:
+/// 1. Save current `fd=1` with `dup` (`saved_stdout`).
+/// 2. Replace `fd=1` with `/dev/tty` via `dup2_stdout` for TUI rendering.
+/// 3. Restore the original `fd=1` on exit.
+///
+/// After restore, writing to `io::stdout()` again goes to the original pipe
+/// (for example `pbcopy`) so the final JSON can be emitted there.
+///
+/// Note:
+/// `stdout` is file descriptor 1 (FD 1), not the screen itself.
+/// Its destination is chosen by the shell when the process starts:
+/// terminal (`cmd`), file (`cmd > out.txt`), or pipe (`cmd | next`).
+/// Therefore, we cannot just write to `stdout` for TUI rendering when it's piped.
+/// Instead, we must write directly to the terminal device (`/dev/tty` on Unix).
+pub struct StdoutRedirect {
+    #[cfg(unix)]
+    saved_stdout: Option<OwnedFd>,
+}
+
+impl StdoutRedirect {
+    pub fn try_new_for_tui(write_to_stdout: bool) -> anyhow::Result<Self> {
+        if !write_to_stdout || io::stdout().is_terminal() {
+            return Ok(Self {
+                #[cfg(unix)]
+                saved_stdout: None,
+            });
+        }
+
+        #[cfg(unix)]
+        {
+            let tty = File::options()
+                .read(true)
+                .write(true)
+                .open("/dev/tty")
+                .map_err(|e| anyhow!("Failed to open /dev/tty for TUI rendering: {e}"))?;
+
+            let saved_fd = dup(stdout()).map_err(|e| anyhow!("Failed to duplicate stdout: {e}"))?;
+            dup2_stdout(&tty).map_err(|e| anyhow!("Failed to redirect stdout to /dev/tty: {e}"))?;
+
+            Ok(Self {
+                saved_stdout: Some(saved_fd),
+            })
+        }
+
+        #[cfg(not(unix))]
+        {
+            Err(anyhow!(
+                "`--write-to-stdout` with piped stdout is not supported on this platform"
+            ))
+        }
+    }
+
+    pub fn restore(&mut self) -> anyhow::Result<()> {
+        #[cfg(unix)]
+        if let Some(saved_stdout) = self.saved_stdout.take() {
+            dup2_stdout(&saved_stdout).map_err(|e| anyhow!("Failed to restore stdout: {e}"))?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Drop for StdoutRedirect {
+    fn drop(&mut self) {
+        let _ = self.restore();
+    }
+}