Add --snapshot-to CLI option for state dumps on 'd' key

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased]
 
+### Added
+* Add `--snapshot-to` CLI option for saving the current state snapshot to a file when pressing `d`
+
 ### Fixed
 
 * Fix Ctrl+C handling to use SIGINT signal instead of keypress #491 - @chiranjeevi-max

src/cli.rs

@@ -32,6 +32,10 @@ pub struct Opt {
     /// Enable debug logging to a file
     pub log_to: Option<PathBuf>,
 
+    #[arg(long, value_hint = ValueHint::FilePath)]
+    /// Write a current-state snapshot to this file when the user presses 'd'
+    pub snapshot_to: Option<PathBuf>,
+
     #[command(flatten)]
     pub verbosity: Verbosity<InfoLevel>,
 

src/main.rs

@@ -54,7 +54,12 @@ fn main() -> eyre::Result<()> {
         )?;
     }
 
-    let os_input = os::get_input(opts.interface.as_deref(), !opts.no_resolve, opts.dns_server)?;
+    let os_input = os::get_input(
+        opts.interface.as_deref(),
+        !opts.no_resolve,
+        opts.dns_server,
+        opts.snapshot_to.as_deref(),
+    )?;
     if opts.raw {
         let terminal_backend = RawTerminalBackend {};
         start(terminal_backend, os_input, opts);
@@ -89,6 +94,7 @@ pub struct OsInputOutput {
     pub terminal_events: Box<dyn Iterator<Item = Event> + Send>,
     pub dns_client: Option<dns::Client>,
     pub write_to_stdout: Box<dyn FnMut(&str) + Send>,
+    pub write_to_file: Option<Box<dyn FnMut(&str) + Send>>,
 }
 
 pub fn start<B>(terminal_backend: B, os_input: OsInputOutput, opts: Opt)
@@ -124,6 +130,8 @@ where
     let network_utilization = Arc::new(Mutex::new(Utilization::new()));
     let ui = Arc::new(Mutex::new(Ui::new(terminal_backend, &opts)));
 
+    let mut write_to_file = os_input.write_to_file;
+
     let display_handler = thread::Builder::new()
         .name("display_handler".to_string())
         .spawn({
@@ -267,6 +275,16 @@ where
                             table_cycle_offset.store(new, Ordering::SeqCst);
                             ui.draw(paused, elapsed_time, new);
                         }
+                        Event::Key(KeyEvent {
+                            modifiers: KeyModifiers::NONE,
+                            code: KeyCode::Char('d'),
+                            kind: KeyEventKind::Press,
+                            ..
+                        }) => {
+                            if let Some(writer) = write_to_file.as_mut() {
+                                ui.output_text(writer);
+                            }
+                        }
                         _ => (),
                     };
                 }

src/os/shared.rs

@@ -1,6 +1,8 @@
 use std::{
+    fs::OpenOptions,
     io::{self, ErrorKind, Write},
     net::Ipv4Addr,
+    path::Path,
     time::{self, Duration},
 };
 
@@ -105,10 +107,26 @@ fn create_write_to_stdout() -> Box<dyn FnMut(&str) + Send> {
     })
 }
 
+pub fn create_write_to_file(path: &Path) -> eyre::Result<Box<dyn FnMut(&str) + Send>> {
+    let mut file = OpenOptions::new()
+        .create(true)
+        .append(true)
+        .open(path)
+        .map_err(|err| eyre!("Failed to open file in {path:?} due to {err}"))?;
+    let path = path.to_path_buf();
+
+    Ok(Box::new(move |output| {
+        if let Err(e) = writeln!(&mut file, "{output}") {
+            warn!("Failed to write dump to file {path:?}: {e}");
+        }
+    }))
+}
+
 pub fn get_input(
     interface_name: Option<&str>,
     resolve: bool,
     dns_server: Option<Ipv4Addr>,
+    snapshot_path: Option<&Path>,
 ) -> eyre::Result<OsInputOutput> {
     // get the user's requested interface, if any
     // IDEA: allow requesting multiple interfaces
@@ -219,13 +237,17 @@ pub fn get_input(
     };
 
     let write_to_stdout = create_write_to_stdout();
+    let write_to_file = snapshot_path
+        .map(|path| create_write_to_file(path))
+        .transpose()?;
 
     Ok(OsInputOutput {
         interfaces_with_frames,
         get_open_sockets,
         terminal_events: Box::new(TerminalEvents),
         dns_client,
         write_to_stdout,
+        write_to_file,
     })
 }
 

src/tests/cases/test_utils.rs

@@ -271,6 +271,7 @@ pub fn os_input_output_factory(
         terminal_events: keyboard_events,
         dns_client,
         write_to_stdout,
+        write_to_file: None,
     }
 }