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exit.go
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exit.go
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// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
/*
Package exit provides an alternative to os.Exit(int).
Unlike os.Exit(int), exit.Return(int) will run deferred functions before
terminating. It's effectively like a return from main(), except you can specify
the exit code.
Defer a call to exit.Recover() or exit.RecoverAll() at the beginning of main().
Use exit.Return(int) to initiate an exit.
func main() {
defer exit.Recover()
defer cleanup()
...
if err != nil {
// Return from main() with a non-zero exit code,
// making sure to run deferred cleanup.
exit.Return(1)
}
...
}
All functions deferred *after* defer exit.Recover()/RecoverAll() will be
executed before the exit. This is why the defer for this package should
be the first statement in main().
NOTE: This mechanism only works if exit.Return() is called from the same
goroutine that deferred exit.Recover(). Usually this means Return() should
only be used from within main(), or within functions that are only ever
called from main(). See Recover() and Return() for more details.
*/
package exit
import (
"os"
log "github.com/golang/glog"
"github.com/youtube/vitess/go/tb"
)
type exitCode int
var (
exitFunc = os.Exit // can be faked out for testing
)
// Recover should be deferred as the first line of main(). It recovers the
// panic initiated by Return and converts it to a call to os.Exit. Any
// functions deferred after Recover in the main goroutine will be executed
// prior to exiting. Recover will re-panic anything other than the panic it
// expects from Return.
func Recover() {
doRecover(recover(), false)
}
// RecoverAll can be deferred instead of Recover as the first line of main().
// Instead of re-panicking, RecoverAll will absorb any panic and convert it to
// an error log entry with a stack trace, followed by a call to os.Exit(255).
func RecoverAll() {
doRecover(recover(), true)
}
func doRecover(err interface{}, recoverAll bool) {
if err == nil {
return
}
switch code := err.(type) {
case exitCode:
exitFunc(int(code))
default:
if recoverAll {
log.Errorf("panic: %v", tb.Errorf("%v", err))
exitFunc(255)
} else {
panic(err)
}
}
}
// Return initiates a panic that sends the return code to the deferred Recover,
// executing other deferred functions along the way. When the panic reaches
// Recover, the return code will be passed to os.Exit. This should only be
// called from the main goroutine.
func Return(code int) {
panic(exitCode(code))
}