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149 lines
4.3 KiB
Markdown
149 lines
4.3 KiB
Markdown
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jWalterWeatherman
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=================
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Seamless printing to the terminal (stdout) and logging to a io.Writer
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(file) that’s as easy to use as fmt.Println.
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Graphic by [JonnyEtc](http://jonnyetc.deviantart.com/art/And-That-s-Why-You-Always-Leave-a-Note-315311422)
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JWW is primarily a wrapper around the excellent standard log library. It
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provides a few advantages over using the standard log library alone.
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1. Ready to go out of the box.
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2. One library for both printing to the terminal and logging (to files).
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3. Really easy to log to either a temp file or a file you specify.
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I really wanted a very straightforward library that could seamlessly do
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the following things.
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1. Replace all the println, printf, etc statements thoughout my code with
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something more useful
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2. Allow the user to easily control what levels are printed to stdout
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3. Allow the user to easily control what levels are logged
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4. Provide an easy mechanism (like fmt.Println) to print info to the user
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which can be easily logged as well
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5. Due to 2 & 3 provide easy verbose mode for output and logs
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6. Not have any unnecessary initialization cruft. Just use it.
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# Usage
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## Step 1. Use it
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Put calls throughout your source based on type of feedback.
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No initialization or setup needs to happen. Just start calling things.
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Available Loggers are:
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* TRACE
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* DEBUG
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* INFO
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* WARN
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* ERROR
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* CRITICAL
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* FATAL
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These each are loggers based on the log standard library and follow the
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standard usage. Eg.
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```go
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import (
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jww "github.com/spf13/jwalterweatherman"
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)
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...
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if err != nil {
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// This is a pretty serious error and the user should know about
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// it. It will be printed to the terminal as well as logged under the
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// default thresholds.
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jww.ERROR.Println(err)
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}
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if err2 != nil {
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// This error isn’t going to materially change the behavior of the
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// application, but it’s something that may not be what the user
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// expects. Under the default thresholds, Warn will be logged, but
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// not printed to the terminal.
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jww.WARN.Println(err2)
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}
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// Information that’s relevant to what’s happening, but not very
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// important for the user. Under the default thresholds this will be
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// discarded.
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jww.INFO.Printf("information %q", response)
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```
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NOTE: You can also use the library in a non-global setting by creating an instance of a Notebook:
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```go
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notepad = jww.NewNotepad(jww.LevelInfo, jww.LevelTrace, os.Stdout, ioutil.Discard, "", log.Ldate|log.Ltime)
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notepad.WARN.Println("Some warning"")
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```
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_Why 7 levels?_
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Maybe you think that 7 levels are too much for any application... and you
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are probably correct. Just because there are seven levels doesn’t mean
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that you should be using all 7 levels. Pick the right set for your needs.
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Remember they only have to mean something to your project.
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## Step 2. Optionally configure JWW
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Under the default thresholds :
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* Debug, Trace & Info goto /dev/null
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* Warn and above is logged (when a log file/io.Writer is provided)
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* Error and above is printed to the terminal (stdout)
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### Changing the thresholds
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The threshold can be changed at any time, but will only affect calls that
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execute after the change was made.
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This is very useful if your application has a verbose mode. Of course you
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can decide what verbose means to you or even have multiple levels of
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verbosity.
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```go
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import (
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jww "github.com/spf13/jwalterweatherman"
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)
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if Verbose {
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jww.SetLogThreshold(jww.LevelTrace)
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jww.SetStdoutThreshold(jww.LevelInfo)
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}
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```
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Note that JWW's own internal output uses log levels as well, so set the log
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level before making any other calls if you want to see what it's up to.
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### Setting a log file
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JWW can log to any `io.Writer`:
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```go
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jww.SetLogOutput(customWriter)
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```
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# More information
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This is an early release. I’ve been using it for a while and this is the
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third interface I’ve tried. I like this one pretty well, but no guarantees
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that it won’t change a bit.
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I wrote this for use in [hugo](https://gohugo.io). If you are looking
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for a static website engine that’s super fast please checkout Hugo.
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