shitbox/src/cmd/which/mod.rs

use super::Cmd;
use clap::{Arg, Command};
use std::{env, fs::File, io, os::unix::prelude::MetadataExt, path::PathBuf, process};

#[derive(Debug, Default)]
pub struct Which;

impl Cmd for Which {
    fn cli(&self) -> clap::Command {
        Command::new("which")
            .about("Write the full path of COMMAND(s) to standard output")
            .author("Nathan Fisher")
            .version(env!("CARGO_PKG_VERSION"))
            .arg(Arg::new("COMMAND").num_args(1..))
    }

    fn run(&self, matches: Option<&clap::ArgMatches>) -> Result<(), Box<dyn std::error::Error>> {
        let Some(matches) = matches else {
            return Err(Box::new(io::Error::new(io::ErrorKind::Other, "no input")));
        };
        let rawpath = if let Ok(p) = env::var("PATH") {
            p
        } else {
            "/usr/bin:/bin".to_string()
        };
        let path: Vec<_> = rawpath.split(':').collect();
        let mut failures = 0;
        if let Some(commands) = matches.get_many::<String>("COMMAND") {
            for command in commands {
                if let Some(p) = which(command, &path) {
                    println!("{p}");
                } else {
                    println!("which: no {} in ({})", command, &rawpath);
                    failures += 1;
                }
            }
        } else {
            let _res = self.cli().print_help();
            process::exit(255);
        }
        if failures > 0 {
            process::exit(failures);
        } else {
            Ok(())
        }
    }

    fn path(&self) -> Option<crate::Path> {
        Some(crate::Path::UsrBin)
    }
}

fn which(command: &str, path: &[&str]) -> Option<String> {
    for p in path {
        let file = [p, command].iter().collect::<PathBuf>();
        if file.exists() {
            if let Ok(exe) = File::open(&file) {
                if let Ok(meta) = exe.metadata() {
                    let mode = meta.mode();
                    let myuid = unsafe { libc::geteuid() };
                    let mygroups = crate::pw::get_gids();
                    // we own the file and it has u+x
                    if myuid == meta.uid() && mode & 0o100 != 0 {
                        return Some(format!("{}", file.display()));
                    // file has ug+x
                    } else if mode & 0o110 != 0 {
                        if let Ok(groups) = mygroups {
                            // one of our groups owns the file
                            if groups.contains(&meta.gid()) {
                                return Some(format!("{}", file.display()));
                            }
                        }
                    // the file has uga+x
                    } else if mode & 0o111 != 0 {
                        return Some(format!("{}", file.display()));
                    }
                }
            }
        }
    }
    None
}