pwcat: add password database dump utility

Cargo.toml

@@ -8,6 +8,13 @@ license.workspace = true
 name = "awk"
 path = "src/main.rs"
 
+[[bin]]
+name = "pwcat"
+path = "src/bin/pwcat.rs"
+
+[target.'cfg(unix)'.dependencies]
+libc = "0.2"
+
 [workspace.package]
 version = "0.1.0"
 license = "MIT OR Apache-2.0"

src/bin/pwcat.rs

@@ -0,0 +1,101 @@
+// This file is part of the uutils awk package.
+//
+// For the full copyright and license information, please view the LICENSE
+// files that was distributed with this source code.
+
+//! Dump the password database in `/etc/passwd` format for gawk library routines.
+//!
+//! Behavior matches the `pwcat` helper described in the GNU Awk User's Guide:
+//! <https://www.gnu.org/software/gawk/manual/html_node/Passwd-Functions.html>
+//!
+//! Uses `getpwent()`/`endpwent()` so NSS sources beyond local files (LDAP, SSSD,
+//! systemd-userdb, etc.) are included, as required by routines such as
+//! `passwd.awk`.
+//!
+//! Platforms without a password database get an empty dump and a successful exit.
+
+#[cfg(unix)]
+use std::io::{self, Write};
+use std::process::ExitCode;
+
+#[cfg(unix)]
+fn main() -> ExitCode {
+    match run() {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(err) if err.kind() == io::ErrorKind::BrokenPipe => ExitCode::SUCCESS,
+        Err(err) => {
+            let _ = writeln!(io::stderr(), "pwcat: {err}");
+            ExitCode::FAILURE
+        }
+    }
+}
+
+#[cfg(not(unix))]
+fn main() -> ExitCode {
+    ExitCode::SUCCESS
+}
+
+#[cfg(unix)]
+fn run() -> io::Result<()> {
+    struct EndPwent;
+
+    impl Drop for EndPwent {
+        fn drop(&mut self) {
+            // SAFETY: pairs with `setpwent` below; `pwcat` is single-threaded.
+            unsafe {
+                libc::endpwent();
+            }
+        }
+    }
+
+    let mut out = io::stdout().lock();
+
+    // SAFETY: `getpwent`/`setpwent`/`endpwent` share process-global state and are
+    // not thread-safe. `pwcat` is a single-threaded helper, so exclusive use is OK.
+    unsafe {
+        libc::setpwent();
+    }
+    let _end = EndPwent;
+
+    loop {
+        // SAFETY: see note above; pointer is only used while non-null and before
+        // the next `getpwent`/`endpwent` call.
+        let passwd = unsafe { libc::getpwent() };
+        if passwd.is_null() {
+            break;
+        }
+        // SAFETY: `getpwent` returned a non-null pointer to a valid `passwd`.
+        let passwd = unsafe { &*passwd };
+
+        write_field(&mut out, passwd.pw_name)?;
+        out.write_all(b":")?;
+        write_field_or_star(&mut out, passwd.pw_passwd)?;
+        write!(out, ":{}:{}:", passwd.pw_uid, passwd.pw_gid)?;
+        write_field(&mut out, passwd.pw_gecos)?;
+        out.write_all(b":")?;
+        write_field(&mut out, passwd.pw_dir)?;
+        out.write_all(b":")?;
+        write_field(&mut out, passwd.pw_shell)?;
+        out.write_all(b"\n")?;
+    }
+
+    Ok(())
+}
+
+#[cfg(unix)]
+fn write_field(out: &mut impl Write, ptr: *const libc::c_char) -> io::Result<()> {
+    if ptr.is_null() {
+        return Ok(());
+    }
+    // SAFETY: caller guarantees a NUL-terminated C string when non-null.
+    let bytes = unsafe { std::ffi::CStr::from_ptr(ptr) }.to_bytes();
+    out.write_all(bytes)
+}
+
+#[cfg(unix)]
+fn write_field_or_star(out: &mut impl Write, ptr: *const libc::c_char) -> io::Result<()> {
+    if ptr.is_null() {
+        return out.write_all(b"*");
+    }
+    write_field(out, ptr)
+}

tests/by-util/test_pwcat.rs

@@ -0,0 +1,95 @@
+// This file is part of the uutils awk package.
+//
+// For the full copyright and license information, please view the LICENSE
+// files that was distributed with this source code.
+
+use std::process::{Command, Stdio};
+
+use crate::{TESTS_BINARY, ucmd};
+
+#[cfg_attr(
+    not(target_os = "linux"),
+    ignore = "pwcat tests require Linux NSS via getent"
+)]
+#[test]
+fn pwcat_outputs_passwd_database_format() {
+    let result = ucmd().succeeds();
+    let stdout = result.stdout_str();
+
+    assert!(
+        !stdout.is_empty(),
+        "pwcat produced no output; password database may be unavailable in this environment"
+    );
+
+    for line in stdout.lines().filter(|line| !line.is_empty()) {
+        let fields: Vec<&str> = line.split(':').collect();
+        assert_eq!(
+            fields.len(),
+            7,
+            "expected 7 colon-separated fields in line: {line}"
+        );
+        assert!(
+            fields[2].chars().all(|ch| ch.is_ascii_digit()),
+            "expected numeric uid in line: {line}"
+        );
+        assert!(
+            fields[3].chars().all(|ch| ch.is_ascii_digit()),
+            "expected numeric gid in line: {line}"
+        );
+    }
+}
+
+// Regression test for gawk compatibility: pwcat must match the password database
+// format consumed by gawk library routines (see passwd.awk).
+#[cfg_attr(
+    not(target_os = "linux"),
+    ignore = "pwcat tests require Linux NSS via getent"
+)]
+#[test]
+fn pwcat_matches_getent_passwd() {
+    let getent = Command::new("getent")
+        .arg("passwd")
+        .output()
+        .expect("failed to spawn getent; install it or skip this host explicitly");
+    assert!(
+        getent.status.success(),
+        "getent passwd is required for this test (exit {:?}): {}",
+        getent.status.code(),
+        String::from_utf8_lossy(&getent.stderr)
+    );
+
+    let pwcat = ucmd().succeeds();
+    assert_eq!(
+        getent.stdout.as_slice(),
+        pwcat.stdout(),
+        "pwcat output should match getent passwd"
+    );
+}
+
+#[cfg_attr(
+    not(target_os = "linux"),
+    ignore = "pwcat tests require Linux NSS via getent"
+)]
+#[test]
+fn pwcat_ignores_broken_pipe() {
+    let mut child = Command::new(TESTS_BINARY)
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .expect("failed to spawn pwcat");
+
+    // Close the read end immediately so the next write hits EPIPE/BrokenPipe.
+    drop(child.stdout.take());
+
+    let status = child.wait().expect("failed to wait for pwcat");
+    assert!(
+        status.success(),
+        "pwcat should treat broken pipe as success, got {status}"
+    );
+}
+
+#[cfg(not(unix))]
+#[test]
+fn pwcat_without_passwd_database_prints_nothing_and_succeeds() {
+    ucmd().succeeds().no_output();
+}

tests/pwcat.rs

@@ -0,0 +1,27 @@
+// This file is part of the uutils awk package.
+//
+// For the full copyright and license information, please view the LICENSE
+// files that was distributed with this source code.
+
+use std::env;
+
+use uutests::util::TestScenario;
+
+pub const TESTS_BINARY: &str = env!("CARGO_BIN_EXE_pwcat");
+
+#[ctor::ctor(unsafe)]
+fn init() {
+    unsafe {
+        env::set_var("UUTESTS_BINARY_PATH", TESTS_BINARY);
+        env::remove_var("UUTESTS_UTIL_NAME");
+        env::set_var("UUTESTS_UTIL_NAME", "");
+        env::set_var("UUTILS_MULTICALL", "0");
+    }
+}
+
+fn ucmd() -> uutests::util::UCommand {
+    TestScenario::new("pwcat").cmd(TESTS_BINARY)
+}
+
+#[path = "by-util/test_pwcat.rs"]
+mod test_pwcat;