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 Go to latest Published: Jan 4, 2020 License: BSD-2-Clause Imports: 6 Imported by: 2

README

glog Build Status

Go's modified log package with an option to set a loglevel, which will filter the output of logs based on that. (This is a lame attempt to modify GO's original log package (version 1.6.2)), and the logic borrowed from Sirupsen package.

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.

Breaking change because of using pointer to loglevel

Use

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

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,

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,

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.

logger.SetLogLevel(log.WarnLevel) will log Errors and Warnings. Rest are not logged.

logger.SetLogLevel(log.InfoLevel) will log Errors, Warnings and Info. Rest are not logged.

logger.SetLogLevel(log.DebugLevel) will log Errors, Warnings, Info and Debug.

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
package main

import (
    "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.
    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.

Documentation

Overview

Package glog implements a simple logging package. It defines a type, Logger, with methods for formatting output. It also has a predefined 'standard' Logger accessible through helper functions Print[f|ln], Fatal[f|ln], and Panic[f|ln], which are easier to use than creating a Logger manually. That logger writes to standard error and prints the date and time of each logged message. Helper functions (Error|Warn|Info|Debug)ln(), (Error|Warn|Info|Debug)f() and (Error|Warn|Info|Debug)() writes to log only if it meets the required loglevel (ErrorLevel, WarnLevel, InfoLevel, and DebugLevel). The Fatal functions call os.Exit(1) after writing the log message. The Panic functions call panic after writing the log message.

Index

Examples

Constants

View Source 
const (
	// Bits or'ed together to control what's printed.
	// There is no control over the order they appear (the order listed
	// here) or the format they present (as described in the comments).
	// The prefix is followed by a colon only when Llongfile or Lshortfile
	// is specified.
	// For example, flags Ldate | Ltime (or LstdFlags) produce,
	//	2009/01/23 01:23:23 message
	// while flags Ldate | Ltime | Lmicroseconds | Llongfile produce,
	//	2009/01/23 01:23:23.123123 /a/b/c/d.go:23: message
	Ldate         = 1 << iota     // the date in the local time zone: 2009/01/23
	Ltime                         // the time in the local time zone: 01:23:23
	Lmicroseconds                 // microsecond resolution: 01:23:23.123123.  assumes Ltime.
	Llongfile                     // full file name and line number: /a/b/c/d.go:23
	Lshortfile                    // final file name element and line number: d.go:23. overrides Llongfile
	LUTC                          // if Ldate or Ltime is set, use UTC rather than the local time zone
	LstdFlags     = Ldate | Ltime // initial values for the standard logger
)

These flags define which text to prefix to each log entry generated by the Logger.

View Source 
const (
	ErrorLevel uint = iota // 0
	WarnLevel              // 1
	InfoLevel              // 2
	DebugLevel             // 3
)

Constants for defining loglevels

Variables

This section is empty.

Functions

func Debug 

func Debug(v ...interface{})

Debug calls l.Output to print to the standard logger only if standardLogLevel >= constant DebugLevel. Arguments are handled in the manner of fmt.Print.

func Debugf 

func Debugf(format string, v ...interface{})

Debugf calls l.Output to print to the standard logger only if standardLogLevel >= constant DebugLevel. Arguments are handled in the manner of fmt.Printf.

func Debugln 

func Debugln(v ...interface{})

Debugln calls l.Output to print to the standard logger only if standardLogLevel >= constant DebugLevel. Arguments are handled in the manner of fmt.Println.

func Error 

func Error(v ...interface{})

Error calls Output to print to the standard logger only if standardLogLevel >= constant ErrorLevel. Arguments are handled in the manner of fmt.Print.

func Errorf 

func Errorf(format string, v ...interface{})

Errorf calls Output to print to the standard logger only if standardLogLevel >= constant ErrorLevel. Arguments are handled in the manner of fmt.Printf.

func Errorln 

func Errorln(v ...interface{})

Errorln calls Output to print to the standard logger only if standardLogLevel >= constant ErrorLevel. Arguments are handled in the manner of fmt.Println.

func Fatal 

func Fatal(v ...interface{})

Fatal is equivalent to Print() followed by a call to os.Exit(1).

func Fatalf 

func Fatalf(format string, v ...interface{})

Fatalf is equivalent to Printf() followed by a call to os.Exit(1).

func Fatalln 

func Fatalln(v ...interface{})

Fatalln is equivalent to Println() followed by a call to os.Exit(1).

func Flags 

func Flags() int

Flags returns the output flags for the standard logger.

func Info 

func Info(v ...interface{})

Info calls l.Output to print to the standard logger only if standardLogLevel >= constant InfoLevel. Arguments are handled in the manner of fmt.Print.

func Infof 

func Infof(format string, v ...interface{})

Infof calls l.Output to print to the standard logger only if standardLogLevel >= constant InfoLevel. Arguments are handled in the manner of fmt.Printf.

func Infoln 

func Infoln(v ...interface{})

Infoln calls l.Output to print to the standard logger only if standardLogLevel >= constant InfoLevel. Arguments are handled in the manner of fmt.Println.

func Output 

func Output(calldepth int, s string) error

Output writes the output for a logging event. The string s contains the text to print after the prefix specified by the flags of the Logger. A newline is appended if the last character of s is not already a newline. Calldepth is the count of the number of frames to skip when computing the file name and line number if Llongfile or Lshortfile is set; a value of 1 will print the details for the caller of Output.

func Panic 

func Panic(v ...interface{})

Panic is equivalent to Print() followed by a call to panic().

func Panicf 

func Panicf(format string, v ...interface{})

Panicf is equivalent to Printf() followed by a call to panic().

func Panicln 

func Panicln(v ...interface{})

Panicln is equivalent to Println() followed by a call to panic().

func Prefix 

func Prefix() string

Prefix returns the output prefix for the standard logger.

func Print 

func Print(v ...interface{})

Print calls Output to print to the standard logger. Arguments are handled in the manner of fmt.Print.

func Printf 

func Printf(format string, v ...interface{})

Printf calls Output to print to the standard logger. Arguments are handled in the manner of fmt.Printf.

func Println 

func Println(v ...interface{})

Println calls Output to print to the standard logger. Arguments are handled in the manner of fmt.Println.

func SetFlags 

func SetFlags(flag int)

SetFlags sets the output flags for the standard logger.

func SetOutput 

func SetOutput(w io.Writer)

SetOutput sets the output destination for the standard logger.

func SetPrefix 

func SetPrefix(prefix string)

SetPrefix sets the output prefix for the standard logger.

func SetStandardLogLevel 

func SetStandardLogLevel(loglevel *uint)

SetStandardLogLevel changes the default standardLogLevel variable from ErrorLevel to any of (Warn|Info|Debug)Level. This will NOT change the loglevel inside type Logger struct.

func Warn 

func Warn(v ...interface{})

Warn calls Output to print to the standard logger only if standardLogLevel >= constant WarnLevel. Arguments are handled in the manner of fmt.Print.

func Warnf 

func Warnf(format string, v ...interface{})

Warnf calls Output to print to the standard logger only if standardLogLevel >= constant WarnLevel. Arguments are handled in the manner of fmt.Printf.

func Warnln 

func Warnln(v ...interface{})

Warnln calls Output to print to the standard logger only if standardLogLevel >= constant WarnLevel. Arguments are handled in the manner of fmt.Println.

Types

type Logger 

type Logger struct {
	// contains filtered or unexported fields
}

A Logger represents an active logging object that generates lines of output to an io.Writer. Each logging operation makes a single call to the Writer's Write method. A Logger can be used simultaneously from multiple goroutines; it guarantees to serialize access to the Writer.

Example 
var buf bytes.Buffer
Println()
logger := New(&buf, "logger: ", Lshortfile)
//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 is set to ErrorLevel.
Info := InfoLevel
logger.SetLogLevel(&Info)
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
Debug := DebugLevel
SetStandardLogLevel(&Debug)
SetFlags(Lshortfile)
Debugf("This is from %s", strfn)
Printf("%d error from %s", 1, "Error function")
Warnf("%d error from %s", 1, "Error function")
fmt.Println(&buf)

Output:
logger: log_test.go:20: ERROR: Hello, this is 1 Error from Errorf()!
logger: log_test.go:21: ERROR: Hello, this is 1 Error from Error()!
logger: log_test.go:25: ERROR: Hello, This is Error from Errorln!
logger: log_test.go:26: WARN: Hello, This is Warn from Warnln!
logger: log_test.go:27: INFO: Hello, This is Info from Infoln!

func New 

func New(out io.Writer, prefix string, flag int) *Logger

New creates a new Logger. The out variable sets the destination to which log data will be written. The prefix appears at the beginning of each generated log line. The flag argument defines the logging properties. Log level is set as ErrorLevel by default.

func (*Logger) Debug 

func (l *Logger) Debug(v ...interface{})

Debug calls l.Output to print to the logger only if loglevel >= constant DebugLevel. Arguments are handled in the manner of fmt.Print.

func (*Logger) Debugf 

func (l *Logger) Debugf(format string, v ...interface{})

Debugf calls l.Output to print to the logger only if loglevel >= constant DebugLevel. Arguments are handled in the manner of fmt.Printf.

func (*Logger) Debugln 

func (l *Logger) Debugln(v ...interface{})

Debugln calls l.Output to print to the logger only if loglevel >= constant DebugLevel. Arguments are handled in the manner of fmt.Println.

func (*Logger) Error 

func (l *Logger) Error(v ...interface{})

Error calls l.Output to print to the logger only if loglevel >= constant ErrorLevel. Arguments are handled in the manner of fmt.Print.

func (*Logger) Errorf 

func (l *Logger) Errorf(format string, v ...interface{})

Errorf calls l.Output to print to the logger only if loglevel >= constant ErrorLevel. Arguments are handled in the manner of fmt.Printf.

func (*Logger) Errorln 

func (l *Logger) Errorln(v ...interface{})

Errorln calls l.Output to print to the logger only if loglevel >= constant ErrorLevel. Arguments are handled in the manner of fmt.Println.

func (*Logger) Fatal 

func (l *Logger) Fatal(v ...interface{})

Fatal is equivalent to l.Print() followed by a call to os.Exit(1).

func (*Logger) Fatalf 

func (l *Logger) Fatalf(format string, v ...interface{})

Fatalf is equivalent to l.Printf() followed by a call to os.Exit(1).

func (*Logger) Fatalln 

func (l *Logger) Fatalln(v ...interface{})

Fatalln is equivalent to l.Println() followed by a call to os.Exit(1).

func (*Logger) Flags 

func (l *Logger) Flags() int

Flags returns the output flags for the logger.

func (*Logger) Info 

func (l *Logger) Info(v ...interface{})

Info calls l.Output to print to the logger only if loglevel >= constant InfoLevel. Arguments are handled in the manner of fmt.Print.

func (*Logger) Infof 

func (l *Logger) Infof(format string, v ...interface{})

Infof calls l.Output to print to the logger only if loglevel >= constant InfoLevel. Arguments are handled in the manner of fmt.Printf.

func (*Logger) Infoln 

func (l *Logger) Infoln(v ...interface{})

Infoln calls l.Output to print to the logger only if loglevel >= constant InfoLevel. Arguments are handled in the manner of fmt.Println.

func (*Logger) Output 

func (l *Logger) Output(calldepth int, s string) error

Output writes the output for a logging event. The string s contains the text to print after the prefix specified by the flags of the Logger. A newline is appended if the last character of s is not already a newline. Calldepth is used to recover the PC and is provided for generality, although at the moment on all pre-defined paths it will be 2.

func (*Logger) Panic 

func (l *Logger) Panic(v ...interface{})

Panic is equivalent to l.Print() followed by a call to panic().

func (*Logger) Panicf 

func (l *Logger) Panicf(format string, v ...interface{})

Panicf is equivalent to l.Printf() followed by a call to panic().

func (*Logger) Panicln 

func (l *Logger) Panicln(v ...interface{})

Panicln is equivalent to l.Println() followed by a call to panic().

func (*Logger) Prefix 

func (l *Logger) Prefix() string

Prefix returns the output prefix for the logger.

func (*Logger) Print 

func (l *Logger) Print(v ...interface{})

Print calls l.Output to print to the logger. Arguments are handled in the manner of fmt.Print.

func (*Logger) Printf 

func (l *Logger) Printf(format string, v ...interface{})

Printf calls l.Output to print to the logger. Arguments are handled in the manner of fmt.Printf.

func (*Logger) Println 

func (l *Logger) Println(v ...interface{})

Println calls l.Output to print to the logger. Arguments are handled in the manner of fmt.Println.

func (*Logger) SetFlags 

func (l *Logger) SetFlags(flag int)

SetFlags sets the output flags for the logger.

func (*Logger) SetLogLevel 

func (l *Logger) SetLogLevel(loglevel *uint)

SetLogLevel overrides the default loglevel of 0 (ErrorLevel) set by the New() function. This log level is used at runtime to determine if a log has to be printed.

func (*Logger) SetOutput 

func (l *Logger) SetOutput(w io.Writer)

SetOutput sets the output destination for the logger.

func (*Logger) SetPrefix 

func (l *Logger) SetPrefix(prefix string)

SetPrefix sets the output prefix for the logger.

func (*Logger) Warn 

func (l *Logger) Warn(v ...interface{})

Warn calls l.Output to print to the logger only if loglevel >= constant WarnLevel. Arguments are handled in the manner of fmt.Print.

func (*Logger) Warnf 

func (l *Logger) Warnf(format string, v ...interface{})

Warnf calls l.Output to print to the logger only if loglevel >= constant WarnLevel. Arguments are handled in the manner of fmt.Printf.

func (*Logger) Warnln 

func (l *Logger) Warnln(v ...interface{})

Warnln calls l.Output to print to the logger only if loglevel >= constant WarnLevel. Arguments are handled in the manner of fmt.Println.

Source Files

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