打印日志
glog
glog原本是google使用C++实现的一个日志模块(glog c++)，go语言出来以后，又实现了一个Go版本的glog。
代码
glog依赖标准包flag，在调用glog的方法之前，需要调用flag.Parse()。
//create: 2017/12/25 14:24:03 change: 2017/12/25 15:08:49 lijiaocn@foxmail.com
package main
import (
"flag"
"github.com/golang/glog"
)
func main() {
flag.Parse()
glog.Infof("%s\n", "This is a info")
glog.Warningf("%s\n", "This is a warning")
glog.Errorf("%s\n", "This is a error")
glog.V(1).Infof("%s\n", "This is a v1 log")
glog.V(2).Infof("%s\n", "This is a v2 log")
//this call will make the progress exit.
//glog.Fatalf("%s\n", "This is a fatal")
//this call will make the progress exit.
//glog.Exitf("%s\n", "This is a exit")
}
运行
glog支持以下参数。
$ ./glog -h
Usage of ./glog:
-alsologtostderr
log to standard error as well as files
-log_backtrace_at value
when logging hits line file:N, emit a stack trace
-log_dir string
If non-empty, write log files in this directory
-logtostderr
log to standard error instead of files
-stderrthreshold value
logs at or above this threshold go to stderr
-v value
log level for V logs
-vmodule value
comma-separated list of pattern=N settings for file-filtered logging
glog将日志以文件的形式写入-log_dir指定的目录，使用-log_dir时只有ERROR日志会打印到标准输出，
$ ./glog -log_dir=./log
E1225 15:19:10.514843 83246 main.go:13] This is a error
生成的日志文件：
lijiaos-MacBook-Pro:glog lijiao$ ls log/
glog.ERROR
glog.INFO
glog.WARNING
glog.lijiaos-MacBook-Pro.lijiao.log.ERROR.20171225-151858.83190
glog.lijiaos-MacBook-Pro.lijiao.log.ERROR.20171225-151910.83246
glog.lijiaos-MacBook-Pro.lijiao.log.INFO.20171225-151858.83190
glog.lijiaos-MacBook-Pro.lijiao.log.INFO.20171225-151910.83246
glog.lijiaos-MacBook-Pro.lijiao.log.WARNING.20171225-151858.83190
glog.lijiaos-MacBook-Pro.lijiao.log.WARNING.20171225-151910.83246
参数-logtostderr将所有日志打印到标准输出，不保存到文件中。
$ ./glog -logtostderr
I1225 15:22:11.770424 83995 main.go:11] This is a info
W1225 15:22:11.770510 83995 main.go:12] This is a warning
E1225 15:22:11.770513 83995 main.go:13] This is a error
参数-v指定日志的级别，只打印V(x)中，x小于等于-v指定的数值的日志。
$ ./glog -logtostderr -v 1
I1225 15:28:03.517261 85366 main.go:11] This is a info
W1225 15:28:03.517335 85366 main.go:12] This is a warning
E1225 15:28:03.517339 85366 main.go:13] This is a error
I1225 15:28:03.517342 85366 main.go:14] This is a v1 log
建议
必须要记录的日志使用glog.InfoX、glog.WarningX、glog.ErrorX等函数打印。
用于开发调试的日志使用glov.V().InfoX打印。