ogle 2.2.1

Execute a command periodically, showing the output only when it changes
Documentation 
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// Copyright (C) 2020 Leandro Lisboa Penz <lpenz@lpenz.org>
// This file is subject to the terms and conditions defined in
// file 'LICENSE', which is part of this source code package.

use color_eyre::{Result, eyre::eyre};
use man::prelude::*;
use std::env;
use std::error::Error;
use std::fs::{self, File};
use std::io::Write;
use std::path;

fn generate_man_page<P: AsRef<path::Path>>(outdir: P) -> Result<()> {
    let outdir = outdir.as_ref();
    let man_path = outdir.join("ogle.1");
    let manpage = Manual::new("ogle")
        .about("Run a command-line periodically showing the output only when it changes")
        .author(Author::new("Leandro Lisboa Penz").email("lpenz@lpenz.org"))
        .flag(
            Flag::new()
                .short("-c")
                .long("--shell")
                .help("Invoke the shell on the single command argument"),
        )
        .flag(
            Flag::new()
                .short("-z")
                .long("--until-success")
                .help("Loop until the command exists with success"),
        )
        .option(
            Opt::new("period")
                .short("-p")
                .long("--period")
                .default_value("1")
                .help("Period to sleep between executions"),
        )
        .flag(
            Flag::new()
                .short("-h")
                .long("--help")
                .help("Prints help information"),
        )
        .flag(
            Flag::new()
                .short("-V")
                .long("--version")
                .help("Prints version information"),
        )
        .arg(Arg::new("COMMAND"))
        .arg(Arg::new("[ ARGS ]"))
        .description("ogle runs the provided command and stores its output, and starts printing it only when it differs from the last execution.\n\nA status line shows a progress bar based on the duration of the last execution, and other information.\n\nPress ENTER is pressed and the current execution finishes.")
        .example(
            Example::new()
                .text("Monitor the current directory for changes")
                .command("ogle ls"),
        )
        .example(
            Example::new()
                .text("Show the current time every 3 seconds")
                .command("ogle -p 3 date"),
        )
        .example(
            Example::new()
                .text("Try to connect to an ssh server until it succeeds")
                .command("ogle -z ssh server true"),
        )
        .example(
            Example::new()
                .text("Poor man's top using ps")
                .command("ogle -- /bin/bash -c 'ps -eo %cpu,args --sort -%cpu | head'"),
        )
        .render();
    File::create(man_path)?.write_all(manpage.as_bytes())?;
    Ok(())
}

fn main() -> Result<(), Box<dyn Error>> {
    color_eyre::install()?;
    let mut outdir =
        path::PathBuf::from(env::var_os("OUT_DIR").ok_or_else(|| eyre!("error getting OUT_DIR"))?);
    fs::create_dir_all(&outdir)?;
    generate_man_page(&outdir)?;
    // build/ogle-*/out
    outdir.pop();
    // build/ogle-*
    outdir.pop();
    // build
    outdir.pop();
    // .
    // (either target/release or target/build)
    generate_man_page(&outdir)?;
    Ok(())
}