github.com/jbendotnet/noms@v0.0.0-20190904222105-c43e4293ea92/go/nbs/test/manifest_clobber.go (about)

     1  // Copyright 2016 Attic Labs, Inc. All rights reserved.
     2  // Licensed under the Apache License, version 2.0:
     3  // http://www.apache.org/licenses/LICENSE-2.0
     4  
     5  package main
     6  
     7  import (
     8  	"flag"
     9  	"log"
    10  	"os"
    11  
    12  	"golang.org/x/sys/unix"
    13  )
    14  
    15  func main() {
    16  	flag.Parse()
    17  
    18  	if flag.NArg() < 3 {
    19  		log.Fatalln("Not enough arguments")
    20  	}
    21  
    22  	l, err := os.Create(flag.Arg(0))
    23  	if err != nil {
    24  		log.Fatalln(err)
    25  	}
    26  	defer l.Close()
    27  	// lock released by closing l.
    28  	err = unix.Flock(int(l.Fd()), unix.LOCK_EX|unix.LOCK_NB)
    29  	if err == unix.EWOULDBLOCK {
    30  		return
    31  	}
    32  	if err != nil {
    33  		log.Fatalln(err)
    34  	}
    35  
    36  	// Clobber manifest file at flag.Arg(1) with contents at flag.Arg(2)
    37  	m, err := os.Create(flag.Arg(1))
    38  	if err != nil {
    39  		log.Fatalln(err)
    40  	}
    41  	defer m.Close()
    42  	if _, err = m.WriteString(flag.Arg(2)); err != nil {
    43  		log.Fatalln(err)
    44  	}
    45  }