use std::io::{self, Write}; #[cfg(feature = "paging")] use std::process::Child; use crate::error::*; #[cfg(feature = "paging")] use crate::less::retrieve_less_version; #[cfg(feature = "paging")] use crate::paging::PagingMode; #[derive(Debug)] pub enum OutputType {  #[cfg(feature = "paging")]  Pager(Child),  Stdout(io::Stdout), } impl OutputType {  #[cfg(feature = "paging")]  pub fn from_mode(mode: PagingMode, pager: Option<&str>) -> Result<Self> {  use self::PagingMode::*;  Ok(match mode {  Always => OutputType::try_pager(false, pager)?,  QuitIfOneScreen => OutputType::try_pager(true, pager)?,  _ => OutputType::stdout(),  })  }  /// Try to launch the pager. Fall back to stdout in case of errors.  #[cfg(feature = "paging")]  fn try_pager(quit_if_one_screen: bool, pager_from_config: Option<&str>) -> Result<Self> {  use std::env;  use std::ffi::OsString;  use std::path::PathBuf;  use std::process::{Command, Stdio};  let mut replace_arguments_to_less = false;  let pager_from_env = match (env::var("BAT_PAGER"), env::var("PAGER")) {  (Ok(bat_pager), _) => Some(bat_pager),  (_, Ok(pager)) => {  // less needs to be called with the '-R' option in order to properly interpret the  // ANSI color sequences printed by bat. If someone has set PAGER="less -F", we  // therefore need to overwrite the arguments and add '-R'.  //  // We only do this for PAGER (as it is not specific to 'bat'), not for BAT_PAGER  // or bats '--pager' command line option.  replace_arguments_to_less = true;  Some(pager)  }  _ => None,  };  let pager_from_config = pager_from_config.map(|p| p.to_string());  if pager_from_config.is_some() {  replace_arguments_to_less = false;  }  let pager = pager_from_config  .or(pager_from_env)  .unwrap_or_else(|| String::from("less"));  let pagerflags =  shell_words::split(&pager).chain_err(|| "Could not parse pager command.")?;  match pagerflags.split_first() {  Some((pager_name, args)) => {  let mut pager_path = PathBuf::from(pager_name);  if pager_path.file_stem() == Some(&OsString::from("bat")) {  pager_path = PathBuf::from("less");  }  let is_less = pager_path.file_stem() == Some(&OsString::from("less"));  let mut process = if is_less {  let mut p = Command::new(&pager_path);  if args.is_empty() || replace_arguments_to_less {  p.arg("--RAW-CONTROL-CHARS");  if quit_if_one_screen {  p.arg("--quit-if-one-screen");  }  // Passing '--no-init' fixes a bug with '--quit-if-one-screen' in older  // versions of 'less'. Unfortunately, it also breaks mouse-wheel support.  //  // See: http://www.greenwoodsoftware.com/less/news.530.html  //  // For newer versions (530 or 558 on Windows), we omit '--no-init' as it  // is not needed anymore.  match retrieve_less_version() {  None => {  p.arg("--no-init");  }  Some(version)  if (version < 530 || (cfg!(windows) && version < 558)) =>  {  p.arg("--no-init");  }  _ => {}  }  } else {  p.args(args);  }  p.env("LESSCHARSET", "UTF-8");  p  } else {  let mut p = Command::new(&pager_path);  p.args(args);  p  };  Ok(process  .stdin(Stdio::piped())  .spawn()  .map(OutputType::Pager)  .unwrap_or_else(|_| OutputType::stdout()))  }  None => Ok(OutputType::stdout()),  }  }  pub(crate) fn stdout() -> Self {  OutputType::Stdout(io::stdout())  }  #[cfg(feature = "paging")]  pub(crate) fn is_pager(&self) -> bool {  if let OutputType::Pager(_) = self {  true  } else {  false  }  }  #[cfg(not(feature = "paging"))]  pub(crate) fn is_pager(&self) -> bool {  false  }  pub fn handle(&mut self) -> Result<&mut dyn Write> {  Ok(match *self {  #[cfg(feature = "paging")]  OutputType::Pager(ref mut command) => command  .stdin  .as_mut()  .chain_err(|| "Could not open stdin for pager")?,  OutputType::Stdout(ref mut handle) => handle,  })  } } #[cfg(feature = "paging")] impl Drop for OutputType {  fn drop(&mut self) {  if let OutputType::Pager(ref mut command) = *self {  let _ = command.wait();  }  } }