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//! Does all the magic to have you potentially long output piped through the //! external pager. Similar to what git does for its output. //! //! # Quick Start //! //! ```rust //! extern crate pager; //! use pager::Pager; //! fn main() { //! Pager::new().setup(); //! // The rest of your program goes here //! } //! ``` //! //! Under the hood this forks the current process, connects child' stdout //! to parent's stdin, and then replaces the parent with the pager of choice //! (environment variable PAGER). The child just continues as normal. If PAGER //! environment variable is not present `Pager` probes current PATH for `more`. //! If found it is used as a default pager. //! //! You can control pager to a limited degree. For example you can change the //! environment variable used for finding pager executable. //! //! ```rust //! extern crate pager; //! use pager::Pager; //! fn main() { //! Pager::with_env("MY_PAGER").setup(); //! // The rest of your program goes here //! } //! ``` //! //! Alternatively you can specify directly the desired pager command, exactly //! as it would appear in PAGER environment variable. This is useful if you //! need some specific pager and/or flags (like "less -r") and would like to //! avoid forcing your consumers into modifying their existing PAGER //! configuration just for your application. //! //! ```rust //! extern crate pager; //! use pager::Pager; //! fn main() { //! Pager::with_pager("less -r").setup(); //! // The rest of your program goes here //! } //! ``` //! //! If no suitable pager found `setup()` does nothing and your executable keeps //! running as usual. `Pager` cleans after itself and doesn't leak resources in //! case of setup failure. //! //! If you need to disable pager altogether set environment variable `NOPAGER` and `Pager::setup()` //! will skip initialization. The host application will continue as normal. `Pager::is_on()` will //! reflect the fact that no Pager is active. extern crate errno; extern crate libc; mod utils; use std::ffi::OsString; const DEFAULT_PAGER_ENV: &str = "PAGER"; #[derive(Debug, Default)] pub struct Pager { pager: Option<OsString>, env: Option<String>, on: bool, } impl Pager { /// Creates new instance of pager with default settings pub fn new() -> Self { Pager::with_env(DEFAULT_PAGER_ENV) } /// Creates new instance of pager using `env` environment variable instead of PAGER pub fn with_env(env: &str) -> Self { let pager = utils::find_pager(env); Pager { pager: pager, env: String::from(env).into(), on: true, } } #[deprecated(since = "0.12.0", note = "use with_env() instead")] pub fn env(env: &str) -> Self { Pager::with_env(env) } /// Creates a new pager instance directly specifying the desired pager pub fn with_pager(pager: &str) -> Self { Pager { pager: OsString::from(pager).into(), env: None, on: true, } } /// Gives quick assessment of successful Pager setup pub fn is_on(&self) -> bool { self.on } /// Initiates Pager framework and sets up all the necessary environment for sending standard /// output to the activated pager. pub fn setup(&mut self) { if let Some(ref pager) = self.pager { let (pager_stdin, main_stdout) = utils::pipe(); let pid = utils::fork(); match pid { -1 => { // Fork failed utils::close(pager_stdin); utils::close(main_stdout); self.on = false } 0 => { // I am child utils::dup2(main_stdout, libc::STDOUT_FILENO); utils::close(pager_stdin); } _ => { // I am parent utils::dup2(pager_stdin, libc::STDIN_FILENO); utils::close(main_stdout); utils::execvp(pager); } } } else { self.on = false; } } }