feat(sysctl): support displaying only the given parameters

systeroid-core/src/sysctl.rs

@@ -176,8 +176,17 @@ impl Sysctl {
     }
 
     /// Prints the available kernel parameters to the given output.
-    pub fn print_all<W: Write>(&self, output: &mut W, colored: bool) -> Result<()> {
-        for parameter in &self.parameters {
+    pub fn display<W: Write>(
+        &self,
+        output: &mut W,
+        names: Vec<String>,
+        colored: bool,
+    ) -> Result<()> {
+        for parameter in self
+            .parameters
+            .iter()
+            .filter(|param| names.is_empty() || names.iter().any(|name| param.name == *name))
+        {
             if colored {
                 writeln!(
                     output,

systeroid/src/args.rs

@@ -21,6 +21,8 @@ pub struct Args {
     pub display_all: bool,
     /// Disable colored output.
     pub no_color: bool,
+    /// Parameter names.
+    pub param_names: Vec<String>,
 }
 
 impl Args {
@@ -45,8 +47,10 @@ impl Args {
             .map_err(|e| eprintln!("error: {}", e))
             .ok()?;
 
-        let display_all =
-            matches.opt_present("a") || matches.opt_present("A") || matches.opt_present("X");
+        let display_all = matches.opt_present("a")
+            || matches.opt_present("A")
+            || matches.opt_present("X")
+            || !matches.free.is_empty();
 
         if matches.opt_present("h") || !display_all {
             let usage = opts.usage_with_format(|opts| {
@@ -64,6 +68,7 @@ impl Args {
                 kernel_docs: matches.opt_str("d").map(PathBuf::from),
                 display_all,
                 no_color: matches.opt_present("no-color"),
+                param_names: matches.free,
             })
         }
     }

systeroid/src/lib.rs

@@ -22,7 +22,7 @@ pub fn run(args: Args) -> Result<()> {
     }
 
     if args.display_all {
-        sysctl.print_all(&mut stdout, !args.no_color)?;
+        sysctl.display(&mut stdout, args.param_names, !args.no_color)?;
     }
 
     Ok(())