Log file created at: 2016/03/12 17:32:05 Running on machine: kltao-mac Binary: Built with gc go1.4.2 for darwin/amd64 Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg E0312 17:32:05.568597 22052 glog.go:15] This is a Error log
这个时候如果你打开另外两个INFO和WARNING的log文件，会发现WARNING日志文件中除了WARNING信息还记录了Error信息（This is a Error log），而INFO日志文件中则记录了所有的log信息（This is a Info/Warning/Error log）。很容易理解，这些log是有等级的（ERROR>WARNING>INFO），高等级的日志内容会同时会被记录到低等级的日志文件中去。那么glog提供了一个等级呢？答案是4个，除了上面提出的3个，还有一个FALTAL。 这时候又有一个问题来了，为什么第3处的日志信息没有记录下来呢？不急，这个时候如下重新执行一下。就可以在新的INFO日志文件中找到了对应的信息了。
// By default, all log statements write to files in a temporary directory. // This package provides several flags that modify this behavior. // As a result, flag.Parse must be called before any logging is done. // // -logtostderr=false // Logs are written to standard error instead of to files. // -alsologtostderr=false // Logs are written to standard error as well as to files. // -stderrthreshold=ERROR // Log events at or above this severity are logged to standard // error as well as to files. // -log_dir="" // Log files will be written to this directory instead of the // default temporary directory. // // Other flags provide aids to debugging. // // -log_backtrace_at="" // When set to a file and line number holding a logging statement, // such as // -log_backtrace_at=gopherflakes.go:234 // a stack trace will be written to the Info log whenever execution // hits that statement. (Unlike with -vmodule, the ".go" must be // present.) // -v=0 // Enable V-leveled logging at the specified level. // -vmodule="" // The syntax of the argument is a comma-separated list of pattern=N, // where pattern is a literal file name (minus the ".go" suffix) or // "glob" pattern and N is a V level. For instance, // -vmodule=gopher*=3 // sets the V level to 3 in all Go files whose names begin "gopher".
func V(level Level) Verbose { // This function tries hard to be cheap unless there's work to do. // The fast path is two atomic loads and compares.
// Here is a cheap but safe test to see if V logging is enabled globally. if logging.verbosity.get() >= level { return Verbose(true) }
// It's off globally but it vmodule may still be set. // Here is another cheap but safe test to see if vmodule is enabled. if atomic.LoadInt32(&logging.filterLength) > 0 { // Now we need a proper lock to use the logging structure. The pcs field // is shared so we must lock before accessing it. This is fairly expensive, // but if V logging is enabled we're slow anyway. logging.mu.Lock() defer logging.mu.Unlock() if runtime.Callers(2, logging.pcs[:]) == 0 { return Verbose(false) } v, ok := logging.vmap[logging.pcs[0]] if !ok { v = logging.setV(logging.pcs[0]) } return Verbose(v >= level) } return Verbose(false) }
func (v Verbose) Info(args ...interface{}) { if v { logging.print(infoLog, args...) } }
func (v Verbose) Infoln(args ...interface{}) { if v { logging.println(infoLog, args...) } }
func (v Verbose) Infof(format string, args ...interface{}) { if v { logging.printf(infoLog, format, args...) } }