feat(app): check for alternate locations for kernel documentation

systeroid-core/src/parsers.rs

@@ -6,6 +6,12 @@ use systeroid_parser::parser::Parser;
 use systeroid_parser::regex::RegexBuilder;
 
 lazy_static! {
+    /// Possible locations for the Linux kernel documentation.
+    pub static ref KERNEL_DOCS_PATH: Vec<&'static Path> = vec![
+        Path::new("/usr/share/doc/linux/"),
+        Path::new("/usr/share/doc/linux-docs/")
+    ];
+
     /// Pre-defined parsers for parsing the kernel documentation.
     pub static ref PARSERS: Vec<Parser<'static>> = vec![
         Parser {

systeroid/src/app.rs

@@ -1,9 +1,10 @@
 use std::env;
 use std::io::{self, Stdout};
-use std::path::Path;
+use std::path::PathBuf;
 use std::process::{Command, Stdio};
 use systeroid_core::config::AppConfig;
 use systeroid_core::error::Result;
+use systeroid_core::parsers::KERNEL_DOCS_PATH;
 use systeroid_core::sysctl::Sysctl;
 
 /// Application controller.
@@ -37,19 +38,22 @@ impl<'a> App<'a> {
     }
 
     /// Updates the documentation for kernel parameters.
-    fn fetch_documentation(&mut self, kernel_docs: &Path) -> Result<()> {
-        if !kernel_docs.exists() {
-            eprintln!(
-                "warning: `linux kernel documentation is not found in path: {:?}`",
-                kernel_docs.to_string_lossy()
-            );
+    pub fn update_documentation(&mut self, kernel_docs: Option<&PathBuf>) -> Result<()> {
+        let mut kernel_docs_path = KERNEL_DOCS_PATH.clone();
+        if let Some(path) = kernel_docs {
+            kernel_docs_path.insert(0, path);
         }
-        self.sysctl.update_docs(kernel_docs)
+        for path in KERNEL_DOCS_PATH.iter() {
+            if path.exists() {
+                return self.sysctl.update_docs(path);
+            }
+        }
+        eprintln!("warning: `Linux kernel documentation cannot be found. Please specify a path via '-d' argument`",);
+        Ok(())
     }
 
     /// Displays the documentation of a parameter.
-    pub fn display_documentation(&mut self, param_name: &str, kernel_docs: &Path) -> Result<()> {
-        self.fetch_documentation(kernel_docs)?;
+    pub fn display_documentation(&mut self, param_name: &str) -> Result<()> {
         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

@@ -17,7 +17,7 @@ For more details see {bin}(8)."#;
 #[derive(Debug, Default)]
 pub struct Args {
     /// Path of the Linux kernel documentation.
-    pub kernel_docs: PathBuf,
+    pub kernel_docs: Option<PathBuf>,
     /// Display type of the variables.
     pub display_type: DisplayType,
     /// Whether if the unknown variable errors should be ignored.
@@ -48,7 +48,7 @@ impl Args {
         opts.optopt(
             "d",
             "docs",
-            "set the path of the kernel documentation\n(default: /usr/share/doc/linux/)",
+            "set the path of the kernel documentation",
             "<path>",
         );
         opts.optflag("h", "help", "display this help and exit");
@@ -87,11 +87,7 @@ impl Args {
                 DisplayType::Default
             };
             Some(Args {
-                kernel_docs: PathBuf::from(
-                    matches
-                        .opt_str("d")
-                        .unwrap_or_else(|| String::from("/usr/share/doc/linux/")),
-                ),
+                kernel_docs: matches.opt_str("d").map(PathBuf::from),
                 display_type,
                 ignore_errors: matches.opt_present("e"),
                 param_to_explain: matches.opt_str("explain"),

systeroid/src/lib.rs

@@ -24,7 +24,8 @@ pub fn run(args: Args) -> Result<()> {
     let mut app = App::new(&mut sysctl, &config.app);
 
     if let Some(param) = args.param_to_explain {
-        app.display_documentation(&param, &args.kernel_docs)?;
+        app.update_documentation(args.kernel_docs.as_ref())?;
+        app.display_documentation(&param)?;
     } else if args.param_names.is_empty() {
         app.display_parameters()?;
     } else {