src/tools/file_logger.rs: class to log into files

src/tools.rs

@@ -28,6 +28,10 @@ pub mod borrow;
 pub mod fs;
 pub mod tty;
 
+#[macro_use]
+mod file_logger;
+pub use file_logger::*;
+
 /// Macro to write error-handling blocks (like perl eval {})
 ///
 /// #### Example:

src/tools/file_logger.rs

@@ -0,0 +1,73 @@
+use failure::*;
+use chrono::Local;
+use std::io::Write;
+
+/// Log messages with timestamps into files
+///
+/// Logs messages to file, and optionaly to standart output.
+///
+///
+/// #### Example:
+/// ```
+/// #[macro_use] extern crate proxmox_backup;
+/// # use failure::*;
+/// use proxmox_backup::tools::FileLogger;
+///
+/// let mut log = FileLogger::new("test.log", true).unwrap();
+/// flog!(log, "A simple log: {}", "Hello!");
+/// ```
+
+
+pub struct FileLogger {
+    file: std::fs::File,
+    to_stdout: bool,
+}
+
+/// Log messages to [FileLogger](tools/struct.FileLogger.html)
+#[macro_export]
+macro_rules! flog {
+    ($log:expr, $($arg:tt)*) => ({
+        $log.log(format!($($arg)*));
+    })
+}
+
+impl FileLogger {
+
+    pub fn new(file_name: &str, to_stdout: bool) -> Result<Self, Error> {
+
+        let file = std::fs::OpenOptions::new()
+            .read(true)
+            .write(true)
+            .create_new(true)
+            .open(file_name)?;
+
+        Ok(Self { file , to_stdout })
+    }
+
+    pub fn log<S: AsRef<str>>(&mut self, msg: S) {
+
+        let msg = msg.as_ref();
+
+        let mut stdout = std::io::stdout();
+        if self.to_stdout {
+            stdout.write(msg.as_bytes()).unwrap();
+            stdout.write(b"\n").unwrap();
+        }
+
+
+        let line = format!("{}: {}\n", Local::now().format("%b %e %T"), msg);
+        self.file.write(line.as_bytes()).unwrap();
+    }
+}
+
+impl std::io::Write for FileLogger {
+    fn write(&mut self, buf: &[u8]) -> Result<usize, std::io::Error> {
+        if self.to_stdout { let _ = std::io::stdout().write(buf); }
+        self.file.write(buf)
+    }
+
+    fn flush(&mut self) -> Result<(), std::io::Error> {
+        if self.to_stdout { let _ = std::io::stdout().flush(); }
+        self.file.flush()
+    }
+}