README
¶
Go Logger Package
A lightweight and customizable logging package for Go. This package provides support for different log levels, output streams, formatted logs, and error handling, making it easy to integrate logging into your application.
Features
- Support for log levels:
DEBUG,INFO,WARNING,ERROR,FATAL,OFF - Customizable log message and error prefixes
- Separate output writers for standard logs and errors
- Easy-to-use functions for logging formatted messages
- Error checking with built-in logging for
ERRORandFATALlevels - Fatal logs that exit the program
Installation
go get github.com/cyrus2281/go-logger
Usage
Using the Default Logger
The default logger writes to os.Stdout and os.Stderr and has the log level set to INFO.
All of which can be customized using the SetOutputWriters, SetLogLevel, and SetPrefixFormatters methods.
package main
import (
"os"
"github.com/cyrus2281/go-logger/logger"
)
func main() {
// Logging examples
logger.Infoln("This is an info message")
logger.Warningln("This is a warning message")
logger.Errorln("This is an error message")
}
Basic Logger Setup
You can create a new logger using the NewLogger function by specifying the log level and output writers:
package main
import (
"os"
"github.com/cyrus2281/go-logger/logger"
)
func main() {
// Create a logger with INFO level
log := logger.NewLogger(logger.INFO, os.Stdout, os.Stderr)
// Logging examples
log.Infoln("This is an info message")
log.Warningln("This is a warning message")
log.Errorln("This is an error message")
}
Customizing Log Prefixes
You can set prefixes for standard log messages and error messages:
func formatter(level int) string {
currentDate := time.Now().Format("2006-01-02")
return fmt.Sprintf("[%s] [%d] ", currentDate, level)
}
log.SetPrefixFormatter(formatter)
log.SetErrorPrefixFormatter(formatter)
log.Infoln("Application started")
log.Errorln("Failed to connect to database")
Log Levels
The package supports the following log levels, allowing you to filter messages based on importance:
DEBUGINFOWARNINGERRORFATALOFF
log.SetLogLevel(logger.WARNING)
log.Debugln("This will not be logged")
log.Infoln("This will not be logged")
log.Warningln("This will be logged")
log.Errorln("This will be logged")
Formatted Logs
You can log formatted messages using the DebugF, InfoF, WarningF, ErrorF, and FatalF methods.
log.InfoF("User %s logged in at %s", "john_doe", "10:00 AM")
log.ErrorF("Failed to load file: %s", "config.yaml")
Error Checking
The logger provides utility methods for checking errors and logging them automatically:
err := errors.New("connection failed")
log.CheckError(err) // Logs if `err` is not nil
fatalErr := errors.New("fatal error")
log.CheckFatal(fatalErr) // Logs and exits the program if `fatalErr` is not nil
Log Level Behavior
The log level controls which messages will be printed based on their importance:
| Log Level | Logs Debug | Logs Info | Logs Warning | Logs Error | Logs Fatal |
|---|---|---|---|---|---|
DEBUG |
✔ | ✔ | ✔ | ✔ | ✔ |
INFO |
✖ | ✔ | ✔ | ✔ | ✔ |
WARNING |
✖ | ✖ | ✔ | ✔ | ✔ |
ERROR |
✖ | ✖ | ✖ | ✔ | ✔ |
FATAL |
✖ | ✖ | ✖ | ✖ | ✔ |
OFF |
✖ | ✖ | ✖ | ✖ | ✖ |
Advanced Usage
Custom Output Writers
You can direct standard and error logs to different output writers (e.g., files, network streams, etc.).
var outBuf, errBuf bytes.Buffer
log.SetOutputWriters(&outBuf, &errBuf)
log.Infoln("This will be written to outBuf")
log.Errorln("This will be written to errBuf")
Contributing
Contributions are welcome! Feel free to submit issues or pull requests to help improve this package.
Running Tests
To run the tests for this package, use:
go test ./...
License
This project is licensed under the Apache v2.0 License - see the LICENSE file for details.
Documentation
¶
Index ¶
- Constants
- func CheckError(err error)
- func CheckErrorF(err error, format string, message ...any)
- func CheckErrorln(err error)
- func CheckFatal(err error)
- func CheckFatalF(err error, format string, message ...any)
- func CheckFatalln(err error)
- func Debug(message ...any)
- func DebugF(format string, message ...any)
- func Debugln(message ...any)
- func Error(message ...any)
- func ErrorF(format string, message ...any)
- func Errorln(message ...any)
- func Fatal(message ...any)
- func FatalF(format string, message ...any)
- func Fatalln(message ...any)
- func GetLogLevel() int
- func Info(message ...any)
- func InfoF(format string, message ...any)
- func Infoln(message ...any)
- func NewDefaultLogger() logger
- func NewLogger(level int, outputWriter io.Writer, errOutputWriter io.Writer) logger
- func SetErrorOutputWriter(writer io.Writer)
- func SetErrorPrefixFormatter(errorPrefixFormatter func(level int) string)
- func SetLogLevel(level int)
- func SetOutputWriter(writer io.Writer)
- func SetOutputWriters(writer io.Writer, errWriter io.Writer)
- func SetPrefixFormatter(prefixFormatter func(level int) string)
- func SetPrefixFormatters(prefixFormatter func(level int) string, ...)
- func Warning(message ...any)
- func WarningF(format string, message ...any)
- func Warningln(message ...any)
Constants ¶
const ( DEBUG = iota INFO WARNING ERROR FATAL OFF )
Variables ¶
This section is empty.
Functions ¶
func CheckError ¶
func CheckError(err error)
CheckError checks error and logs with ERROR level to error output if not nil
func CheckErrorF ¶
CheckErrorF checks error and logs formatted message with ERROR level to error output if not nil
func CheckErrorln ¶
func CheckErrorln(err error)
CheckErrorln checks error and logs with ERROR level to error output if not nil and a newline
func CheckFatal ¶
func CheckFatal(err error)
CheckFatal checks error and logs with FATAL level to error output and exits with 1 if not nil
func CheckFatalF ¶
CheckFatalF checks error and logs formatted message with FATAL level to error output and exits with 1 if not nil
func CheckFatalln ¶
func CheckFatalln(err error)
CheckFatalln checks error and logs with FATAL level to error output and exits with 1 if not nil and a newline
func Errorln ¶
func Errorln(message ...any)
Errorln logs with ERROR level to error output and a newline
func Fatal ¶
func Fatal(message ...any)
Fatal logs with FATAL level to error output and exits with 1
func Fatalln ¶
func Fatalln(message ...any)
Fatalln logs with FATAL level to error output and exits with 1 and a newline
func NewDefaultLogger ¶
func NewDefaultLogger() logger
NewDefaultLogger creates a new logger instance with default log level, standard output and error output
func NewLogger ¶
NewLogger creates a new logger instance with the specified log level, output writer and error output writer
func SetErrorOutputWriter ¶
SetErrorOutputWriter sets the output writer for error output
func SetErrorPrefixFormatter ¶ added in v1.1.0
SetErrorPrefixFormatter sets the prefix for the error log message
func SetOutputWriter ¶
SetOutputWriter sets the output writer for standard output
func SetOutputWriters ¶
SetOutputWriters sets the output writers for standard output and error output
func SetPrefixFormatter ¶ added in v1.1.0
SetPrefixFormatter sets the prefix formatter for the log message
func SetPrefixFormatters ¶ added in v1.1.0
func SetPrefixFormatters(prefixFormatter func(level int) string, errorPrefixFormatter func(level int) string)
SetPrefixFormatters sets the prefix formatters for the log message and the error log message
Types ¶
This section is empty.
Source Files