feat(args): add --pattern argument for matching parameters

systeroid-core/src/config.rs

@@ -56,6 +56,7 @@ impl Default for AppConfig {
         }
     }
 }
+
 /// Sysctl configuration.
 #[derive(Debug, Default)]
 pub struct SysctlConfig {

systeroid-core/src/lib.rs

@@ -5,6 +5,9 @@
 #[macro_use]
 extern crate lazy_static;
 
+/// Export regex crate.
+pub use systeroid_parser::regex;
+
 /// Kernel parameter handler.
 pub mod sysctl;
 

systeroid/src/app.rs

@@ -6,6 +6,7 @@ use systeroid_core::cache::{Cache, CacheData};
 use systeroid_core::config::AppConfig;
 use systeroid_core::error::Result;
 use systeroid_core::parsers::KERNEL_DOCS_PATH;
+use systeroid_core::regex::Regex;
 use systeroid_core::sysctl::Sysctl;
 
 /// Label for caching the kernel parameters.
@@ -35,11 +36,18 @@ impl<'a> App<'a> {
         })
     }
 
-    /// Displays all of the available kernel modules.
-    pub fn display_parameters(&mut self) -> Result<()> {
+    /// Displays all of the available kernel parameters.
+    pub fn display_parameters(&mut self, pattern: Option<Regex>) -> Result<()> {
         self.sysctl
             .parameters
             .iter()
+            .filter(|parameter| {
+                if let Some(pattern) = &pattern {
+                    pattern.is_match(&parameter.name)
+                } else {
+                    true
+                }
+            })
             .try_for_each(|parameter| parameter.display_value(self.config, &mut self.stdout))
     }
 

systeroid/src/args.rs

@@ -2,6 +2,7 @@ use getopts::Options;
 use std::env;
 use std::path::PathBuf;
 use systeroid_core::display::DisplayType;
+use systeroid_core::regex::Regex;
 
 /// Help message for the arguments.
 const HELP_MESSAGE: &str = r#"
@@ -24,6 +25,8 @@ pub struct Args {
     pub ignore_errors: bool,
     /// Do not pipe output into a pager.
     pub no_pager: bool,
+    /// Pattern for matching the parameters.
+    pub pattern: Option<Regex>,
     /// Parameter to explain.
     pub param_to_explain: Option<String>,
     /// Parameter names.
@@ -41,6 +44,12 @@ impl Args {
         opts.optflag("e", "ignore", "ignore unknown variables errors");
         opts.optflag("N", "names", "print variable names without values");
         opts.optflag("n", "values", "print only values of the given variable(s)");
+        opts.optopt(
+            "r",
+            "pattern",
+            "select setting that match expression",
+            "<expression>",
+        );
         opts.optopt(
             "E",
             "explain",
@@ -94,7 +103,10 @@ impl Args {
                 display_type,
                 ignore_errors: matches.opt_present("e"),
                 no_pager: matches.opt_present("P"),
-                param_to_explain: matches.opt_str("explain"),
+                pattern: matches
+                    .opt_str("r")
+                    .map(|v| Regex::new(&v).expect("invalid regex")),
+                param_to_explain: matches.opt_str("E"),
                 param_names: matches.free,
             })
         }

systeroid/src/lib.rs

@@ -28,7 +28,7 @@ pub fn run(args: Args) -> Result<()> {
         app.update_documentation(args.kernel_docs.as_ref())?;
         app.display_documentation(&param)?;
     } else if args.param_names.is_empty() {
-        app.display_parameters()?;
+        app.display_parameters(args.pattern)?;
     } else {
         for param_name in args.param_names {
             app.process_parameter(param_name)?;