Add `printenv` applet

src/cmd/mod.rs

@@ -31,6 +31,7 @@ mod mountpoint;
 mod mv;
 mod nologin;
 mod nproc;
+mod printenv;
 mod pwd;
 mod rev;
 mod rm;
@@ -85,6 +86,7 @@ pub fn get(name: &str) -> Option<Box<dyn Cmd>> {
         "mountpoint" => Some(Box::new(mountpoint::Mountpoint::default())),
         "nologin" => Some(Box::new(nologin::Nologin::default())),
         "nproc" => Some(Box::new(nproc::Nproc::default())),
+        "printenv" => Some(Box::new(printenv::Printenv::default())),
         "pwd" => Some(Box::new(pwd::Pwd::default())),
         "rev" => Some(Box::new(rev::Rev::default())),
         "rm" => Some(Box::new(rm::Rm::default())),
@@ -101,7 +103,7 @@ pub fn get(name: &str) -> Option<Box<dyn Cmd>> {
     }
 }
 
-pub static COMMANDS: [&str; 35] = [
+pub static COMMANDS: [&str; 36] = [
     "base32",
     "base64",
     "basename",
@@ -125,6 +127,7 @@ pub static COMMANDS: [&str; 35] = [
     "mountpoint",
     "nologin",
     "nproc",
+    "printenv",
     "pwd",
     "rev",
     "rm",

src/cmd/printenv/mod.rs

@@ -0,0 +1,56 @@
+use std::{env, io};
+
+use super::Cmd;
+use clap::{Arg, ArgAction, Command};
+
+#[derive(Debug, Default)]
+pub struct Printenv;
+
+impl Cmd for Printenv {
+    fn cli(&self) -> clap::Command {
+        Command::new("printenv")
+            .about("print all or part of environment")
+            .author("Nathan Fisher")
+            .version(env!("CARGO_PKG_VERSION"))
+            .args([
+                Arg::new("null")
+                    .short('0')
+                    .long("null")
+                    .help("end each output line with NUL, not newline")
+                    .action(ArgAction::SetTrue),
+                Arg::new("var")
+                    .value_name("VARIABLE")
+                    .num_args(1..)
+                    .required(false),
+            ])
+    }
+
+    fn run(&self, matches: Option<&clap::ArgMatches>) -> Result<(), Box<dyn std::error::Error>> {
+        let Some(matches) = matches else {
+            return Err(io::Error::new(io::ErrorKind::Other, "no input").into());
+        };
+        if let Some(vars) = matches.get_many::<String>("var") {
+            for var in vars {
+                let val = env::var(var)?;
+                if matches.get_flag("null") {
+                    print!("{var}={val}\0");
+                } else {
+                    println!("{var}={val}");
+                }
+            }
+        } else {
+            env::vars().for_each(|(var, val)| {
+                if matches.get_flag("null") {
+                    print!("{var}={val}\0");
+                } else {
+                    println!("{var}={val}");
+                }
+            });
+        }
+        Ok(())
+    }
+
+    fn path(&self) -> Option<crate::Path> {
+        Some(crate::Path::UsrBin)
+    }
+}