Add error handling for pacman update

src/main.rs

@@ -11,6 +11,8 @@
     This file contains the primary logic of the application
 */
 
+use std::io;
+
 mod pacman_install_check;
 mod shell_commands;
 
@@ -22,9 +24,21 @@ fn main() {
         return;
     }
 
-    println!("Here we do things");
+    println!("Running pacman update");
+    if let Err(e) = shell_commands::execute_in_sh("pacman -Syu") {
+        match e.kind() {
+            io::ErrorKind::PermissionDenied => {
+                eprintln!("Permission to use pacman has been denied. Please try again with sudo.");
+                return;
+            }
+            _ => {
+                eprintln!("{}", e);
+                return;
+            }
+        }
+    }
 
-    shell_commands::execute_in_sh("sudo pacman -Syu").unwrap();
+    println!("Move onto something else");
 }
 
 fn copyright_notice() -> &'static str {

src/shell_commands.rs

@@ -13,18 +13,36 @@
 
 use std::ffi::OsStr;
 use std::io;
-use std::process::Command;
+use std::io::{ErrorKind, Read};
+use std::process::{Command, Stdio};
 
 pub fn execute_and_display<S: AsRef<OsStr>, I>(cmd: S, args: I) -> io::Result<()>
 where
     I: IntoIterator,
     I::Item: AsRef<OsStr>,
 {
-    let mut child = Command::new(cmd).args(args).spawn()?;
+    let mut child = Command::new(cmd)
+        .args(args)
+        .stderr(Stdio::piped())
+        .spawn()?;
 
     child.wait()?;
 
-    Ok(())
+    if let Some(mut child_stderr) = child.stderr {
+        let mut output = String::new();
+        child_stderr.read_to_string(&mut output)?;
+
+        // TODO: Relocate to future pacman api
+        if output == "error: you cannot perform this operation unless you are root.\n" {
+            Err(io::Error::from(ErrorKind::PermissionDenied))
+        } else if output.is_empty() {
+            Ok(())
+        } else {
+            Err(io::Error::new(ErrorKind::Other, output))
+        }
+    } else {
+        Ok(())
+    }
 }
 
 pub fn execute_in_sh(cmd: &'static str) -> io::Result<()> {