refactor(args): add a default path for linux kernel documentation

systeroid/src/app.rs

@@ -1,5 +1,6 @@
 use std::env;
 use std::io::{self, Stdout};
+use std::path::Path;
 use std::process::{Command, Stdio};
 use systeroid_core::config::Config;
 use systeroid_core::error::Result;
@@ -35,8 +36,20 @@ impl<'a> App<'a> {
             .try_for_each(|parameter| parameter.display_value(&self.config.color, &mut self.stdout))
     }
 
+    /// Updates the documentation for kernel parameters.
+    fn fetch_documentation(&mut self, kernel_docs: &Path) -> Result<()> {
+        if !kernel_docs.exists() {
+            eprintln!(
+                "WARN: Linux kernel documentation is not found in path: {:?}",
+                kernel_docs.to_string_lossy()
+            );
+        }
+        self.sysctl.update_docs(kernel_docs)
+    }
+
     /// Displays the documentation of a parameter.
-    pub fn display_documentation(&mut self, param_name: &str) -> Result<()> {
+    pub fn display_documentation(&mut self, param_name: &str, kernel_docs: &Path) -> Result<()> {
+        self.fetch_documentation(kernel_docs)?;
         if let Some(parameter) = self.sysctl.get_parameter(param_name) {
             let mut fallback_to_default = false;
             let pager = env::var("PAGER").unwrap_or_else(|_| String::from("less"));

systeroid/src/args.rs

@@ -16,7 +16,7 @@ For more details see {bin}(8)."#;
 #[derive(Debug, Default)]
 pub struct Args {
     /// Path of the Linux kernel documentation.
-    pub kernel_docs: Option<PathBuf>,
+    pub kernel_docs: PathBuf,
     /// Parameter to explain.
     pub param_to_explain: Option<String>,
     /// Parameter names.
@@ -41,7 +41,7 @@ impl Args {
         opts.optopt(
             "d",
             "docs",
-            "set the path of the kernel documentation",
+            "set the path of the kernel documentation\n(default: /usr/share/doc/linux/)",
             "<path>",
         );
 
@@ -69,7 +69,11 @@ impl Args {
             None
         } else {
             Some(Args {
-                kernel_docs: matches.opt_str("d").map(PathBuf::from),
+                kernel_docs: PathBuf::from(
+                    matches
+                        .opt_str("d")
+                        .unwrap_or_else(|| String::from("/usr/share/doc/linux/")),
+                ),
                 param_to_explain: matches.opt_str("explain"),
                 param_names: matches.free,
             })

systeroid/src/lib.rs

@@ -19,15 +19,10 @@ pub fn run(args: Args) -> Result<()> {
     let mut config = Config::default();
     config.color.no_color = env::var("NO_COLOR").is_ok();
     let mut sysctl = Sysctl::init()?;
-
-    if let Some(kernel_docs) = args.kernel_docs {
-        sysctl.update_docs(&kernel_docs)?;
-    }
-
     let mut app = App::new(&mut sysctl, &config);
 
     if let Some(param) = args.param_to_explain {
-        app.display_documentation(&param)?;
+        app.display_documentation(&param, &args.kernel_docs)?;
     } else if args.param_names.is_empty() {
         app.display_parameters()?;
     } else {