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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::env("MY_PAGER").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::ok()` 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: String,
ok: bool,
}
impl Pager {
/// Creates new instance of pager with default settings
pub fn new() -> Self {
Pager::env(DEFAULT_PAGER_ENV)
}
/// Creates new instance of pager using `env` environment variable instead of PAGER
pub fn env(env: &str) -> Self {
let pager = utils::find_pager(env);
Pager {
pager: pager,
env: env.into(),
ok: true,
}
}
/// Gives quick assessment of successful Pager setup
pub fn ok(&self) -> bool {
self.ok
}
/// 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.ok = 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);
}
}
}
}
}
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