Implement ctrlaltdel (#31)

* Implement ctrlaltdel

* Add tests for `ctrlaltdel`

* Bless the unit tests on unsupported platforms

src/uu/ctrlaltdel/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "uu_ctrlaltdel"
+version = "0.0.1"
+edition = "2021"
+
+[lib]
+path = "src/ctrlaltdel.rs"
+
+[[bin]]
+name = "ctrlaltdel"
+path = "src/main.rs"
+
+[dependencies]
+uucore = { workspace = true }
+clap = { workspace = true }

src/uu/ctrlaltdel/ctrlaltdel.md

@@ -0,0 +1,7 @@
+# ctrlaltdel
+
+```
+ctrlaltdel hard|soft
+```
+
+set the function of the ctrl-alt-del combination

src/uu/ctrlaltdel/src/ctrlaltdel.rs

@@ -0,0 +1,139 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use clap::{crate_version, Arg, ArgAction, Command};
+use uucore::{error::UResult, format_usage, help_about, help_usage};
+
+const ABOUT: &str = help_about!("ctrlaltdel.md");
+const USAGE: &str = help_usage!("ctrlaltdel.md");
+
+#[cfg(target_os = "linux")]
+const CTRL_ALT_DEL_PATH: &str = "/proc/sys/kernel/ctrl-alt-del";
+
+#[cfg(target_os = "linux")]
+#[uucore::main]
+pub fn uumain(args: impl uucore::Args) -> UResult<()> {
+    let matches: clap::ArgMatches = uu_app().try_get_matches_from(args)?;
+    let pattern = matches.get_one::<String>("pattern");
+    match pattern {
+        Some(x) if x == "hard" => {
+            set_ctrlaltdel(CtrlAltDel::Hard)?;
+        }
+        Some(x) if x == "soft" => {
+            set_ctrlaltdel(CtrlAltDel::Soft)?;
+        }
+        Some(x) => {
+            Err(Error::UnknownArgument(x.clone()))?;
+        }
+        None => {
+            println!("{}", get_ctrlaltdel()?);
+        }
+    }
+
+    Ok(())
+}
+
+#[cfg(not(target_os = "linux"))]
+#[uucore::main]
+pub fn uumain(args: impl uucore::Args) -> UResult<()> {
+    let _matches: clap::ArgMatches = uu_app().try_get_matches_from(args)?;
+
+    Err(uucore::error::USimpleError::new(
+        1,
+        "`ctrlaltdel` is unavailable on current platform.",
+    ))
+}
+
+#[cfg(target_os = "linux")]
+fn get_ctrlaltdel() -> UResult<CtrlAltDel> {
+    let value: i32 = std::fs::read_to_string(CTRL_ALT_DEL_PATH)?
+        .trim()
+        .parse()
+        .map_err(|_| Error::UnknownData)?;
+
+    Ok(CtrlAltDel::from_sysctl(value))
+}
+
+#[cfg(target_os = "linux")]
+fn set_ctrlaltdel(ctrlaltdel: CtrlAltDel) -> UResult<()> {
+    std::fs::write(CTRL_ALT_DEL_PATH, format!("{}\n", ctrlaltdel.to_sysctl()))
+        .map_err(|_| Error::NotRoot)?;
+
+    Ok(())
+}
+
+#[cfg(target_os = "linux")]
+#[derive(Clone, Copy)]
+enum CtrlAltDel {
+    Soft,
+    Hard,
+}
+#[cfg(target_os = "linux")]
+impl CtrlAltDel {
+    /// # Panics
+    /// Panics if value of the parameter `value` is neither `0` nor `1`.
+    fn from_sysctl(value: i32) -> Self {
+        match value {
+            0 => Self::Soft,
+            1 => Self::Hard,
+            _ => unreachable!(),
+        }
+    }
+
+    fn to_sysctl(self) -> i32 {
+        match self {
+            Self::Soft => 0,
+            Self::Hard => 1,
+        }
+    }
+}
+#[cfg(target_os = "linux")]
+impl std::fmt::Display for CtrlAltDel {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Soft => write!(f, "soft"),
+            Self::Hard => write!(f, "hard"),
+        }
+    }
+}
+
+#[cfg(target_os = "linux")]
+#[derive(Debug)]
+enum Error {
+    NotRoot,
+    UnknownArgument(String),
+    UnknownData,
+}
+#[cfg(target_os = "linux")]
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::NotRoot => write!(f, "You must be root to set the Ctrl-Alt-Del behavior"),
+            Self::UnknownArgument(x) => write!(f, "unknown argument: {x}"),
+            Self::UnknownData => write!(f, "unknown data"),
+        }
+    }
+}
+#[cfg(target_os = "linux")]
+impl std::error::Error for Error {}
+#[cfg(target_os = "linux")]
+impl uucore::error::UError for Error {
+    fn code(&self) -> i32 {
+        1
+    }
+
+    fn usage(&self) -> bool {
+        false
+    }
+}
+
+pub fn uu_app() -> Command {
+    Command::new(uucore::util_name())
+        .version(crate_version!())
+        .about(ABOUT)
+        .override_usage(format_usage(USAGE))
+        .infer_long_args(true)
+        .arg(Arg::new("pattern").action(ArgAction::Set))
+}

src/uu/ctrlaltdel/src/main.rs

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+uucore::bin!(uu_ctrlaltdel);