A simple, opinionated logger for command line tools
`ocli` aims at a very simple thing: logging for CLI tools done right. It uses the
`log` crate and the `ansi_term` crate for colors. It provides very few configuration —
at this time, just the expected log level.
## Features
`ocli`:
* logs everything to `stderr`. CLI tools are expected to be usable in a pipe. In that context,
the messages addressed to the user must be written on `stderr` to have a chance to be read
by the user, independently of the log level.
The program outputs that are meant to be used with a pipe shouldn't go through the logging
system, but instead be printed to `stdout`, for example with `println!`.
* shows the `Info` message as plain uncolored text. `Info` is expected to be the normal log
level to display messages that are not highlighting a problem and that are not too verbose
for a standard usage of the tool. Because it is intended for messages that are related
to a normal situation, the messages of that level are not prefixed with the log level.
* prefix the messages with their colored log level for any level other than `Info`. The color
depends on the log level, allowing to quickly locate a message at a specific log level
* displays the module path and line when configured at the `Trace` log level, for all the
messages, even if they are not at the `Trace` log level. The `Trace` log level is used
to help the developer understand where a message comes from, in addition to display a larger
amount of messages.
* disable all colorization in case the `stderr` is not a tty, so the output is not polluted
with unreadable characters when `stderr` is redirected to a file.
## Example with `Info` log level
```rust
#[macro_use] extern crate log;
fn main() {
ocli::init(log::Level::Info).unwrap();
error!("This is printed to stderr, with the 'error: ' prefix colored in red");
warn!("This is printed to stderr, with the 'warn: ' prefix colored in yellow");
info!("This is printed to stderr, without prefix or color");
debug!("This is not printed");
trace!("This is not printed");
}
```
## Example with `Trace` log level
```rust
#[macro_use] extern crate log;
fn main() {
ocli::init(log::Level::Trace).unwrap();
error!("This is printed to stderr, with the 'path(line): error: ' prefix colored in red");
warn!("This is printed to stderr, with the 'path(line): warn: ' prefix colored in yellow");
info!("This is printed to stderr, with the 'path(line): info: ' prefix");
debug!("This is printed to stderr, with the 'path(line): debug: ' prefix colored in blue");
trace!("This is printed to stderr, with the 'path(line): trace: ' prefix colored in magenta");
}
```
and a more realistic example with [hld](https://github.com/glehmann/hld):
