Fix/Refactor based on clippy warnings

Also log errors/warnings to stderr instead of stdout, since swaybar
expects formatted stdout output.

src/args.rs

@@ -1,4 +1,6 @@
 use std::collections::HashMap;
+use std::io;
+use std::io::Write;
 
 pub fn get_args() -> HashMap<String, String> {
     let mut map = HashMap::new();
@@ -19,8 +21,13 @@ pub fn get_args() -> HashMap<String, String> {
 }
 
 pub fn print_usage() {
-    println!("Usage:");
-    println!("  --help\t\t\tPrints help");
-    println!("  --netdev=<device_name>\tCheck network traffic on specified device");
-    println!("  --interval-sec=<seconds>\tOutput at intervals of <seconds> (default 5)");
+    let mut stderr_handle = io::stderr().lock();
+    stderr_handle.write_all(b"Usage:\n").ok();
+    stderr_handle.write_all(b"  --help\t\t\tPrints help\n").ok();
+    stderr_handle
+        .write_all(b"  --netdev=<device_name>\tCheck network traffic on specified device\n")
+        .ok();
+    stderr_handle
+        .write_all(b"  --interval-sec=<seconds>\tOutput at intervals of <seconds> (default 5)\n")
+        .ok();
 }

src/main.rs

@@ -2,6 +2,7 @@ mod args;
 mod proc;
 mod swaybar_object;
 
+use std::io::{self, Write};
 use std::time::Duration;
 use swaybar_object::*;
 
@@ -25,13 +26,22 @@ fn main() {
             if seconds_value > 0 {
                 interval = Duration::from_secs(seconds_value as u64);
             } else {
-                println!(
-                    "WARNING: Invalid --interval-sec=\"{}\", defaulting to 5!",
+                let mut stderr_handle = io::stderr().lock();
+                stderr_handle
+                    .write_all(
+                        format!(
+                            "WARNING: Invalid --interval-sec=\"{}\", defaulting to 5!\n",
                             seconds_value
-                );
+                        )
+                        .as_bytes(),
+                    )
+                    .ok();
             }
         } else {
-            println!("WARNING: Failed to parse --interval-sec=?, defaulting to 5!");
+            let mut stderr_handle = io::stderr().lock();
+            stderr_handle
+                .write_all(b"WARNING: Failed to parse --interval-sec=?, defaulting to 5!\n")
+                .ok();
         }
     }
 
@@ -48,10 +58,16 @@ fn main() {
         // network traffic
         if let Some(net) = &mut net_obj {
             if let Err(e) = net.update() {
-                println!("{}", e);
+                let mut stderr_handle = io::stderr().lock();
+                stderr_handle.write_all(e.to_string().as_bytes()).ok();
                 net_obj = None;
             } else {
-                let netinfo_string = net.get_netstring();
+                let netinfo_result = net.get_netstring();
+                if let Err(e) = netinfo_result {
+                    let mut stderr_handle = io::stderr().lock();
+                    stderr_handle.write_all(e.to_string().as_bytes()).ok();
+                } else {
+                    let netinfo_string = netinfo_result.unwrap();
                     let netinfo_parts: Vec<&str> = netinfo_string.split_whitespace().collect();
 
                     {
@@ -73,13 +89,15 @@ fn main() {
                     }
                 }
             }
+        }
 
         // meminfo
         {
             let meminfo_result = proc::get_meminfo();
             let meminfo_string: String;
             if let Err(e) = meminfo_result {
-                println!("{}", e);
+                let mut stderr_handle = io::stderr().lock();
+                stderr_handle.write_all(format!("{}\n", e).as_bytes()).ok();
                 meminfo_string = String::from("MEMINFO ERROR");
             } else {
                 meminfo_string = meminfo_result.unwrap();
@@ -93,7 +111,8 @@ fn main() {
             let loadavg_result = proc::get_loadavg();
             let loadavg_string: String;
             if let Err(e) = loadavg_result {
-                println!("{}", e);
+                let mut stderr_handle = io::stderr().lock();
+                stderr_handle.write_all(format!("{}\n", e).as_bytes()).ok();
                 loadavg_string = String::from("LOADAVG ERROR");
             } else {
                 loadavg_string = loadavg_result.unwrap();

src/proc.rs

@@ -1,38 +1,47 @@
+use std::fmt::Write;
 use std::fs::File;
 use std::io;
 use std::io::prelude::*;
 
 #[derive(Debug)]
 pub enum Error {
-    IOError(std::io::Error),
-    ParseIntError(std::num::ParseIntError),
-    GenericError(String),
+    IO(std::io::Error),
+    ParseInt(std::num::ParseIntError),
+    Format(std::fmt::Error),
+    Generic(String),
 }
 
 impl From<std::io::Error> for Error {
     fn from(io_error: std::io::Error) -> Self {
-        Self::IOError(io_error)
+        Self::IO(io_error)
     }
 }
 
 impl From<std::num::ParseIntError> for Error {
     fn from(parse_error: std::num::ParseIntError) -> Self {
-        Self::ParseIntError(parse_error)
+        Self::ParseInt(parse_error)
+    }
+}
+
+impl From<std::fmt::Error> for Error {
+    fn from(fmt_error: std::fmt::Error) -> Self {
+        Self::Format(fmt_error)
     }
 }
 
 impl From<String> for Error {
     fn from(string: String) -> Self {
-        Self::GenericError(string)
+        Self::Generic(string)
     }
 }
 
 impl std::fmt::Display for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Error::IOError(e) => e.fmt(f),
-            Error::ParseIntError(e) => e.fmt(f),
-            Error::GenericError(s) => f.write_str(s),
+            Error::IO(e) => e.fmt(f),
+            Error::ParseInt(e) => e.fmt(f),
+            Error::Format(e) => e.fmt(f),
+            Error::Generic(s) => f.write_str(s),
         }
     }
 }
@@ -40,8 +49,8 @@ impl std::fmt::Display for Error {
 impl std::error::Error for Error {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
         match self {
-            Error::IOError(e) => e.source(),
-            Error::ParseIntError(e) => e.source(),
+            Error::IO(e) => e.source(),
+            Error::ParseInt(e) => e.source(),
             _ => None,
         }
     }
@@ -100,7 +109,7 @@ impl NetInfo {
         Ok(())
     }
 
-    pub fn get_netstring(&mut self) -> String {
+    pub fn get_netstring(&mut self) -> Result<String, Error> {
         let down_diff: f64 = (self.down - self.prev_down) as f64;
         self.prev_down = self.down;
         let up_diff: f64 = (self.up - self.prev_up) as f64;
@@ -108,22 +117,22 @@ impl NetInfo {
 
         let mut output = String::new();
         if down_diff > 1024.0 * 1024.0 {
-            output.push_str(&format!("{:.2} MiB ", down_diff / (1024.0 * 1024.0)));
+            write!(&mut output, "{:.2} MiB ", down_diff / (1024.0 * 1024.0))?;
         } else if down_diff > 1024.0 {
-            output.push_str(&format!("{:.2} KiB ", down_diff / 1024.0));
+            write!(&mut output, "{:.2} KiB ", down_diff / 1024.0)?;
         } else {
-            output.push_str(&format!("{:.0} B ", down_diff));
+            write!(&mut output, "{:.0} B ", down_diff)?;
         }
 
         if up_diff > 1024.0 * 1024.0 {
-            output.push_str(&format!("{:.2} MiB", up_diff / (1024.0 * 1024.0)));
+            write!(&mut output, "{:.2} MiB", up_diff / (1024.0 * 1024.0))?;
         } else if up_diff > 1024.0 {
-            output.push_str(&format!("{:.2} KiB", up_diff / 1024.0));
+            write!(&mut output, "{:.2} KiB", up_diff / 1024.0)?;
         } else {
-            output.push_str(&format!("{:.0} B", up_diff));
+            write!(&mut output, "{:.0} B", up_diff)?;
         }
 
-        output
+        Ok(output)
     }
 }
 
@@ -180,7 +189,7 @@ pub fn get_meminfo() -> Result<String, Error> {
             output.push_str("KiB / ");
         }
 
-        output.push_str(&format!("{} ", total));
+        write!(&mut output, "{} ", total)?;
         if is_total_mega {
             output.push_str("MiB");
         } else {