Merge pull request #2 from nohupped/nohupped/use_pointers

use pointers to store loglevel

.travis.yml

@@ -0,0 +1 @@
+language: go

README.md

@@ -1,14 +1,88 @@
-# glog
+# glog [![Build Status](https://travis-ci.org/nohupped/glog.svg?branch=master)](https://travis-ci.org/nohupped/glog)
+
 Go's modified log package with an option to set a loglevel, which will filter the output of logs based on that.
-(This is the modified code from GO's original `log` package at https://github.com/golang/go/tree/master/src/log (version 1.6.2)), and the logic borrowed from https://github.com/Sirupsen/logrus package.
+(This is a lame attempt to modify GO's original [`log` package](https://github.com/golang/go/tree/master/src/log) (version 1.6.2)), and the logic borrowed from [Sirupsen](https://github.com/Sirupsen/logrus) package.
+
+## Why
 
-##### Why!
 I was trying to find a way to log `filename` and `line number` using logrus for obvious debugging purpose, but I failed to get a workaround. I am not using advanced features of `logrus` like `SetFormatter` or `hooks`. `Go`'s native `log` package already provides a feature to log filename and line numbers but it lacks setting a loglevel for filtering logs. I just borrowed and incorporated the idea of using a `loglevel`.
 Newly added methods for `*Logger` like `(Error|Warn|Info|Debug)ln(), (Error|Warn|Info|Debug)f() and (Error|Warn|Info|Debug)()` will only output logs based on the configured loglevel with the helper function `SetLogLevel()`. Accepted log levels are `ErrorLevel, WarnLevel, InfoLevel and DebugLevel` which are of values `int 0, 1, 2, 3` respectively.
 
 Default value of `loglevel` at the time of initing the `*Logger` is set to the lowest level, which is `ErrorLevel`.
 
-##### Reference when setting loglevel:
+## Breaking change because of using pointer to loglevel
+
+Use
+
+```bash
+require github.com/nohupped/glog v0.0.0-20200102070319-ef78151f855d
+```
+
+in the go.mod file to continue using the older version that uses `int` as `loglevel` instead of `*uint`.
+
+* why? To have the convenience of using this logger in `init()` functions and have a global variable that can be modified without calling the `SetStandardLogLevel` or similar functions in every importing sub-packages.
+
+Eg: Package `foo/blah`
+
+```golang
+package blah
+import (
+     // "flag"
+    log "github.com/nohupped/glog"
+)
+
+// Loglevel is the logging handler
+var Loglevel *uint
+
+func init() {
+    // loglevel := flag.Uint("loglevel", uint(glog.InfoLevel), "Loglevel.")
+    // flag.Parse()
+    // Don't do the above 2 lines in init functions. This will mess with go's testing because of https://github.com/golang/go/issues/33774.
+    // flag.Parse() and init() functions doesn't go well.
+    if Loglevel == nil {
+        l := log.ErrorLevel
+        Loglevel = &l
+    }
+    log.SetFlags(log.Lshortfile | log.Ldate | log.Ltime)
+    log.SetStandardLogLevel(Loglevel)
+    log.Infof("Setting loglevel to %d", log.InfoLevel)
+}
+
+```
+
+and in package foo,
+
+```golang
+package main
+
+import(
+    "foo/blah"
+)
+func main(){
+    loglevel := flag.Uint("loglevel", log.InfoLevel, "Loglevel.")
+    flag.Parse()
+    *blah.Loglevel = *loglevel // Dereference and modify the pointer value to update the loglevel globally on all the packages that imports foo/blah.
+}
+```
+
+Now, for another sub-package `foo/extreme_computation`,
+
+```golang
+package extreme_computation
+import(
+    _ "foo/blah"
+    log "github.com/nohupped/glog"
+)
+
+func PvsNP() {
+
+}
+
+```
+
+it will see the updated loglevel from the `main` although the initial loglevel was set in `blah`, and this is because of the `var Loglevel *uint`
+
+### Reference when setting loglevel
 
 `logger.SetLogLevel(log.ErrorLevel)` will log only Errors using the method `log.Error*()`. Any calls to `log.Warn*()`, `log.Info*()` and `log.Debug*()` will not be logged unless the `loglevel` is changed.
 
@@ -20,47 +94,49 @@ Default value of `loglevel` at the time of initing the `*Logger` is set to the l
 
 Note: To disable logging line numbers and file names, set the logger's flag similar to `logger := log.New(&buf, "logger: ", log.Ldate)` instead of `log.Lshortfile` or similar flags.
 
-##### Example:
+#### Example
 
-```
+```golang
 package main
 
 import (
-	"bytes"
-	"fmt"
-	log "github.com/nohupped/glog"
+    "bytes"
+    "fmt"
+    log "github.com/nohupped/glog"
 )
 
 func main() {
-	var buf bytes.Buffer
-	logger := log.New(&buf, "logger: ", log.Lshortfile)
-	// Below two lines to set logging to file
-	//file, _ := os.OpenFile("/tmp/testlog.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
-	//logger.SetOutput(file)
-	strfn := "Errorf()!"
-	logger.Errorf("Hello, this is %d Error from %s", 1, strfn)
-	logger.Error("Hello, this is 1 Error from Error()!")
-	logger.Warnln("Hello, This is from Warnln!") // This will not print because the default loglevel when initiating logger is set to ErrorLevel.
-	logger.SetLogLevel(log.InfoLevel)
-	logger.Errorln("Hello, This is Error from Errorln!")
-	logger.Warnln("Hello, This is Warn from Warnln!")
-	logger.Infoln("Hello, This is Info from Infoln!")
-	logger.Debugln("Hello, This is Debug from Debugln!") // This will not print because loglevel is set to InfoLevel
-
-	log.SetStandardLogLevel(log.DebugLevel) // set std loglevel. This will NOT set the *Logger struct's loglevel.
-	log.SetFlags(log.Lshortfile) // set flags to log. This will add short filename and line number.
-	log.Debugf("This is from %s", strfn)
-	log.Printf("%d error from %s", 1, "Error function")
-	log.Warnf("%d error from %s", 1, "Error function")
-	fmt.Println(&buf)
-
-	fmt.Print(&buf)
-
-	// Output:
-	// logger: main.go:19: ERROR: Hello, this is 1 Error from Errorf()!
-	// logger: main.go:20: ERROR: Hello, this is 1 Error from Error()!
-	// logger: main.go:23: ERROR: Hello, This is Error from Errorln!
-	// logger: main.go:24: WARN: Hello, This is Warn from Warnln!
-	// logger: main.go:25: INFO: Hello, This is Info from Infoln!
+    var buf bytes.Buffer
+    logger := log.New(&buf, "logger: ", log.Lshortfile)
+    // Below two lines to set logging to file
+    //file, _ := os.OpenFile("/tmp/testlog.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
+    //logger.SetOutput(file)
+    strfn := "Errorf()!"
+    logger.Errorf("Hello, this is %d Error from %s", 1, strfn)
+    logger.Error("Hello, this is 1 Error from Error()!")
+    logger.Warnln("Hello, This is from Warnln!") // This will not print because the default loglevel when initiating logger is set to ErrorLevel.
+    il := log.InfoLevel
+    logger.SetLogLevel(&iL)
+    logger.Errorln("Hello, This is Error from Errorln!")
+    logger.Warnln("Hello, This is Warn from Warnln!")
+    logger.Infoln("Hello, This is Info from Infoln!")
+    logger.Debugln("Hello, This is Debug from Debugln!") // This will not print because loglevel is set to InfoLevel
+    dl := log.DebugLevel
+    log.SetStandardLogLevel(&dl) // set std loglevel. This will NOT set the *Logger struct's loglevel.
+    log.SetFlags(log.Lshortfile) // set flags to log. This will add short filename and line number.
+    log.Debugf("This is from %s", strfn)
+    log.Printf("%d error from %s", 1, "Error function")
+    log.Warnf("%d error from %s", 1, "Error function")
+    fmt.Println(&buf)
+
+    fmt.Print(&buf)
+
+    // Output:
+    // logger: main.go:19: ERROR: Hello, this is 1 Error from Errorf()!
+    // logger: main.go:20: ERROR: Hello, this is 1 Error from Error()!
+    // logger: main.go:23: ERROR: Hello, This is Error from Errorln!
+    // logger: main.go:24: WARN: Hello, This is Warn from Warnln!
+    // logger: main.go:25: INFO: Hello, This is Info from Infoln!
 
 ```
+`* Line numbers may vary.`