Add printenv

Cargo.toml

@@ -7,6 +7,10 @@ edition = "2021"
 name = "echo"
 path = "src/echo.rs"
 
+[[bin]]
+name = "printenv"
+path = "src/printenv.rs"
+
 [dependencies]
 aho-corasick = "1.1.3"
 clap = { version = "4.5.20", features = ["derive"] }

README.md

@@ -4,5 +4,5 @@ Implementation of some of the Unix command line utils
 
 Currently implemented:
 ```
-echo
+echo, printenv
 ```

src/printenv.rs

@@ -0,0 +1,43 @@
+#![feature(iter_intersperse)]
+
+use std::io::Write;
+
+use clap::Parser;
+
+/// Utility command to output information
+#[derive(Parser, Debug)]
+#[command(version, about, long_about = None)]
+struct Args {
+	/// End each output line with NUL instead of newline
+	#[arg(short='0', long)]
+	null: bool,
+}
+
+fn main() {
+	let args = Args::parse();
+
+	let mut list: Vec<String> = vec![];
+	for (k, v) in std::env::vars() {
+		list.push(format!("{k}={v}"));
+	}
+
+	let mut data: String;
+
+	if args.null {
+		data = list.join("\0");
+		data.push('\0');
+	} else {
+		data = list.join("\n");
+		data.push('\n');
+	}
+
+	let mut out = std::io::stdout();
+
+	match out.write_all(data.as_bytes()) {
+		Err(e) => {
+			eprintln!("Failed to write to stdout: {e}");
+			std::process::exit(1);
+		},
+		Ok(()) => ()
+	};
+}

tests/printenv.rs

@@ -0,0 +1,28 @@
+use assert_cmd::prelude::*;
+use predicates::prelude::*;
+use std::process::Command;
+
+#[test]
+fn env_capture() -> Result<(), Box<dyn std::error::Error>> {
+	std::env::set_var("TEST_ABC", "brrrr");
+    let mut cmd = Command::cargo_bin("printenv")?;
+
+    cmd.assert()
+        .success()
+        .stdout(predicate::str::contains("TEST_ABC=brrrr\n"));
+
+    Ok(())
+}
+
+#[test]
+fn null_replace() -> Result<(), Box<dyn std::error::Error>> {
+	std::env::set_var("TEST_ABC", "brrrr");
+    let mut cmd = Command::cargo_bin("printenv")?;
+
+	cmd.arg("-0");
+    cmd.assert()
+        .success()
+        .stdout(predicate::str::contains("TEST_ABC=brrrr\0"));
+
+    Ok(())
+}