Pager2 - long output best friend

NOTE

Pager2 is a fork of the pager crate @ 2b7dc4d0/2022-09-22 on 2025-08-19 due to this issue; see also the Forcing the pager example.

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

# #[allow(needless_doctest_main)]
use pager2::Pager;

fn main() {
    Pager::new().setup();
    // The rest of your program goes here
}

Under the hood this forks the current process, connects child's 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.

Custom environment variable

You can control pager to a limited degree. For example you can change the environment variable used for finding pager executable.

# #[allow(needless_doctest_main)]
use pager2::Pager;

fn main() {
    Pager::with_env("MY_PAGER").setup();
    // The rest of your program goes here
}

Alternative fallback

Also you can set alternative default (fallback) pager to be used instead of more. PAGER environment variable (if set) will still have precedence.

# #[allow(needless_doctest_main)]
use pager2::Pager;

fn main() {
    Pager::with_default_pager("pager").setup();
    // The rest of your program goes here
}

If no suitable pager is found, [Pager::setup()] does nothing and your executable keeps running as usual. [Pager] cleans after itself and doesn't leak resources in case of setup failure.

Custom pager command

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.

# #[allow(needless_doctest_main)]
use pager2::Pager;

fn main() {
    Pager::with_pager("less -r").setup();
    // The rest of your program goes here
}

Disabling the pager

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.

Forcing the pager

Sometimes you may want to force the pager to be set even if the output of your executable is not a tty, for example when your executable has a --color always option.

# #[allow(needless_doctest_main)]
use {
    clap::{Parser, ValueEnum},
    pager2::Pager,
    std::io::IsTerminal,
    which::which,
};

#[derive(Parser)]
struct Options {
    /// Color
    #[arg(long, default_value = "auto")]
    color: Color,
}

#[derive(Clone, PartialEq, ValueEnum)]
enum Color {
    Auto,
    Always,
    Never,
}

fn main() {
    let options = Options::parse();
    if which("bat").is_ok() {
        let mut bat = String::from("bat -p");
        let always = options.color == Color::Always;
        if (options.color == Color::Auto && std::io::stdout().is_terminal()) || always {
            // Syntax highlight JSON output if stdout is a TTY or color set to always
            bat.push_str(" -l json");
        }
        if always {
            // Force color
            bat.push_str(" --color always");

            Pager::with_pager(&bat).no_skip().setup();
        } else {
            Pager::with_pager(&bat).setup();
        }
    }

    // The rest of your program goes here
}