[chg] log to file

specify a log file as 1st argument and the input will also be written to
that file. timestamp will be without ansi color codes.

src/main.rs

@@ -1,8 +1,24 @@
 use chrono::prelude::*;
-use std::io::{stdin, stdout, ErrorKind, Read, StdoutLock, Write};
+use std::{
+    env::args,
+    fs::File,
+    io::{stdin, stdout, Error as IoError, Read, StdoutLock, Write},
+};
+
+type LogtimesResult = Result<(), IoError>;
 
 #[inline(always)]
-fn print_time(output: &mut StdoutLock) -> Result<(), std::io::Error> {
+fn print_time<T>(output: &mut T) -> LogtimesResult
+where
+    T: Write,
+{
+    let date_now = Local::now().format("%H:%M:%S%.9f");
+
+    write!(output, "[{}] ", &date_now)
+}
+
+#[inline(always)]
+fn print_time_color(output: &mut StdoutLock) -> Result<(), std::io::Error> {
     let date_now = Local::now().format("%H:%M:%S%.9f");
 
     let color_green = "\x1b\x5b\x30\x3b\x33\x32\x6d";
@@ -12,13 +28,15 @@ fn print_time(output: &mut StdoutLock) -> Result<(), std::io::Error> {
 }
 
 #[inline(always)]
-fn print_delete_line(output: &mut StdoutLock) -> Result<(), std::io::Error> {
+fn print_delete_line(output: &mut StdoutLock) -> LogtimesResult {
     // tput dl1 und tput hpa 0
     let bytes = "\x1b\x5b\x4d\x1b\x5b\x31\x47";
     write!(output, "{}", bytes)
 }
 
-fn run() -> Result<(), std::io::Error> {
+fn run() -> LogtimesResult {
+    let mut log_file = args().nth(1).map(|f| File::create(f).unwrap());
+
     let out = stdout();
     let mut output = out.lock();
 
@@ -30,24 +48,28 @@ fn run() -> Result<(), std::io::Error> {
     let mut linebuf = Vec::with_capacity(64 * 1024);
 
     loop {
-        if let Err(e) = input.read_exact(&mut buf) {
+        // read 1 char
-            if e.kind() == ErrorKind::UnexpectedEof {
+        input.read_exact(&mut buf)?;
-                return Err(e);
-            } else {
-                output.flush()?;
-                return Ok(());
-            }
-        }
 
+        // push that char to the "current line" buffer
         linebuf.push(buf[0]);
 
+        // we encounter a newline -> delete the line and write it new as:
+        //     [timestamp] actual content\n
+        //  also write the line to the log file if there is one
         if buf[0] == 0xa {
             print_delete_line(&mut output)?;
-            print_time(&mut output)?;
+            print_time_color(&mut output)?;
             output.write_all(&linebuf)?;
-
             output.flush()?;
 
+            if let Some(ref mut f) = log_file {
+                print_time(f)?;
+                f.write_all(&linebuf)?;
+                f.flush()?;
+            };
+
+            // clear line buffer so it is fresh for the next line
             linebuf.clear();
             continue;
         }