chore: Add a helper function for executing commands (#660)

src/utils.rs

@@ -1,6 +1,7 @@
 use std::fs::File;
 use std::io::{Read, Result};
 use std::path::Path;
+use std::process::Command;
 
 /// Return the string contents of a file
 pub fn read_file<P: AsRef<Path>>(file_name: P) -> Result<String> {
@@ -10,3 +11,97 @@ pub fn read_file<P: AsRef<Path>>(file_name: P) -> Result<String> {
     file.read_to_string(&mut data)?;
     Ok(data)
 }
+
+#[derive(Debug)]
+pub struct CommandOutput {
+    pub stdout: String,
+    pub stderr: String,
+}
+
+impl PartialEq for CommandOutput {
+    fn eq(&self, other: &Self) -> bool {
+        self.stdout == other.stdout && self.stderr == other.stderr
+    }
+}
+
+/// Execute a command and return the output on stdout and stderr if sucessful
+pub fn exec_cmd(cmd: &str, args: &[&str]) -> Option<CommandOutput> {
+    log::trace!("Executing command '{:?}' with args '{:?}'", cmd, args);
+    match Command::new(cmd).args(args).output() {
+        Ok(output) => {
+            let stdout_string = String::from_utf8(output.stdout).unwrap();
+            let stderr_string = String::from_utf8(output.stderr).unwrap();
+
+            if !output.status.success() {
+                log::trace!("Non-zero exit code '{:?}'", output.status.code());
+                log::trace!("stdout: {}", stdout_string);
+                log::trace!("stderr: {}", stderr_string);
+                return None;
+            }
+
+            Some(CommandOutput {
+                stdout: stdout_string,
+                stderr: stderr_string,
+            })
+        }
+        Err(_) => None,
+    }
+}
+
+#[cfg(test)]
+#[cfg(not(windows))] // While the exec_cmd should work on Windows these tests assume a Unix-like environment.
+mod tests {
+    use super::*;
+
+    #[test]
+    fn exec_no_output() {
+        let result = exec_cmd("true", &[]);
+        let expected = Some(CommandOutput {
+            stdout: String::from(""),
+            stderr: String::from(""),
+        });
+
+        assert_eq!(result, expected)
+    }
+
+    #[test]
+    fn exec_with_output_stdout() {
+        let result = exec_cmd("/bin/echo", &["-n", "hello"]);
+        let expected = Some(CommandOutput {
+            stdout: String::from("hello"),
+            stderr: String::from(""),
+        });
+
+        assert_eq!(result, expected)
+    }
+
+    #[test]
+    fn exec_with_output_stderr() {
+        let result = exec_cmd("/bin/sh", &["-c", "echo hello >&2"]);
+        let expected = Some(CommandOutput {
+            stdout: String::from(""),
+            stderr: String::from("hello\n"),
+        });
+
+        assert_eq!(result, expected)
+    }
+
+    #[test]
+    fn exec_with_output_both() {
+        let result = exec_cmd("/bin/sh", &["-c", "echo hello; echo world >&2"]);
+        let expected = Some(CommandOutput {
+            stdout: String::from("hello\n"),
+            stderr: String::from("world\n"),
+        });
+
+        assert_eq!(result, expected)
+    }
+
+    #[test]
+    fn exec_with_non_zero_exit_code() {
+        let result = exec_cmd("false", &[]);
+        let expected = None;
+
+        assert_eq!(result, expected)
+    }
+}