Add option to specify custom format

Author: aswinkarthik

README.md

@@ -4,18 +4,6 @@ tztail (TimeZoneTAIL) allows you to view logs in the timezone you want.
 
 > This project is work in progress
 
-## Usecase
-
-This tool can be used to convert timestamps in a log to any desired timezone while tailing logs. Eg. In case your logs are in UTC and you want to view it in a different timezone say. Asia/Kolkata (IST), pipe the logs through `tztail`.
-
-```bash
-## Example usage
-$ cat somelog # A log in UTC
-2014-11-28T12:00:09+00:00 I | some log
-$ tail somelog | tztail --timezone Asia/Kolkata
-2014-11-28T17:30:09+05:30 I | some log # timestamps alone converted to IST
-```
-
 ## Usage
 
 ```bash
@@ -27,13 +15,46 @@ USAGE:
 
 OPTIONS:
     -t, --timezone <TIMEZONE>    Sets the timezone in which output should be printed
+    -f, --format <FORMAT>        Custom format for parsing dates
     -h, --help                   Prints help information
     -V, --version                Prints version information
 ```
 
-It reads from _STDIN_ as of now.
+## Usecase
+
+This tool can be used to convert timestamps in a log to any desired timezone while tailing logs. Eg. In case your logs are in UTC and you want to view it in a different timezone say. Asia/Kolkata (IST), pipe the logs through `tztail`.
+
+```bash
+## Example usage
+$ cat somelog # A log in UTC
+2018-11-03 19:47:20.279044 I mvcc: finished scheduled compaction at 104794 (took 748.443µs)
+2018-11-03 19:52:20.282913 I mvcc: store.index: compact 105127
+
+$ cat somelog | tztail --timezone Asia/Kolkata # Timestamps converted to IST
+2018-11-04 01:17:20.279044 I mvcc: finished scheduled compaction at 104794 (took 748.443µs)
+2018-11-04 01:22:20.282913 I mvcc: store.index: compact 105127
+```
+
+It allows to specify a custom format as well.
+
+```bash
+## Example usage
+$ cat somelog # A log in non-standard format
+2018-11-03 20:07:20 mvcc: store.index: compact 106120
+2018-11-03 20:07:20 mvcc: finished scheduled compaction at 106120 (took 933.25µs)
+
+$ cat somelog | tztail -t Asia/Kolkata -f "%Y-%m-%d %H:%M:%S"
+2018-11-04 01:37:20 mvcc: store.index: compact 106120
+2018-11-04 01:37:20 mvcc: finished scheduled compaction at 106120 (took 933.25µs)
+```
+
+## Features
+
+- It reads from _STDIN_ as of now.
+- Supports few standard formats with which auto detection is done when parsing logs.
+- Supports specifying custom format for parsing in case it is a non-standard format. See [here](https://docs.rs/chrono/0.4.6/chrono/format/strftime/index.html#specifiers) for formats.
 
-## Supported formats
+## Autodetectable formats
 
 | Name                  | Example                         |
 | --------------------- | ------------------------------- |
@@ -44,8 +65,8 @@ It reads from _STDIN_ as of now.
 
 ## Roadmap
 
-* [ ] Support all standard datetime formats.
-* [ ] Allow custom datetime format.
+* [x] Support all standard datetime formats.
+* [x] Allow custom datetime format.
 * [ ] Allow specifying source timezone (currently supports only UTC).
 * [ ] Auto-detect source timezone if possible.
 * [ ] Add option to read from file.

src/main.rs

@@ -13,15 +13,13 @@ use parser::Parser;
 use std::io;
 use std::io::BufRead;
 
-fn run(timezone: &str) {
+fn run<P: Parser>(p: P) {
     let stdin = io::stdin();
 
-    let p = parser::new_utcparser(timezone);
-
     for line in stdin.lock().lines() {
         match line {
             Ok(content) => println!("{}", p.parse(&content)),
-            Err(err) => println!("{}", err),
+            Err(err) => eprintln!("{}", err),
         }
     }
 }
@@ -42,10 +40,22 @@ fn main() {
                 .required(true)
                 .takes_value(true)
                 .help("Sets the timezone in which output should be printed"),
+        ).arg(
+            Arg::with_name("format")
+                .long("format")
+                .short("f")
+                .value_name("FORMAT")
+                .required(false)
+                .takes_value(true)
+                .help("Custom format for parsing dates"),
         );
 
     let matches = app.get_matches();
     let timezone = matches.value_of("timezone").expect("Please pass timezone");
+    let custom_format = matches.value_of("format");
 
-    run(timezone);
+    match custom_format {
+        Some(format) => run(parser::new_fixedformatutcparser(timezone, format)),
+        None => run(parser::new_utcparser(timezone)),
+    };
 }