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os.go
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os.go
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package common
import (
"bufio"
"fmt"
"io"
"io/ioutil"
"os"
"os/exec"
"os/signal"
"path/filepath"
"strings"
"syscall"
)
var gopath string
// GoPath returns GOPATH env variable value. If it is not set, this function
// will try to call `go env GOPATH` subcommand.
func GoPath() string {
if gopath != "" {
return gopath
}
path := os.Getenv("GOPATH")
if len(path) == 0 {
goCmd := exec.Command("go", "env", "GOPATH")
out, err := goCmd.Output()
if err != nil {
panic(fmt.Sprintf("failed to determine gopath: %v", err))
}
path = string(out)
}
gopath = path
return path
}
// TrapSignal catches the SIGTERM and executes cb function. After that it exits
// with code 1.
func TrapSignal(cb func()) {
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt, syscall.SIGTERM)
go func() {
for sig := range c {
fmt.Printf("captured %v, exiting...\n", sig)
if cb != nil {
cb()
}
os.Exit(1)
}
}()
select {}
}
// Kill the running process by sending itself SIGTERM.
func Kill() error {
p, err := os.FindProcess(os.Getpid())
if err != nil {
return err
}
return p.Signal(syscall.SIGTERM)
}
func Exit(s string) {
fmt.Printf(s + "\n")
os.Exit(1)
}
func EnsureDir(dir string, mode os.FileMode) error {
if _, err := os.Stat(dir); os.IsNotExist(err) {
err := os.MkdirAll(dir, mode)
if err != nil {
return fmt.Errorf("Could not create directory %v. %v", dir, err)
}
}
return nil
}
func IsDirEmpty(name string) (bool, error) {
f, err := os.Open(name)
if err != nil {
if os.IsNotExist(err) {
return true, err
}
// Otherwise perhaps a permission
// error or some other error.
return false, err
}
defer f.Close()
_, err = f.Readdirnames(1) // Or f.Readdir(1)
if err == io.EOF {
return true, nil
}
return false, err // Either not empty or error, suits both cases
}
func FileExists(filePath string) bool {
_, err := os.Stat(filePath)
return !os.IsNotExist(err)
}
func ReadFile(filePath string) ([]byte, error) {
return ioutil.ReadFile(filePath)
}
func MustReadFile(filePath string) []byte {
fileBytes, err := ioutil.ReadFile(filePath)
if err != nil {
Exit(Fmt("MustReadFile failed: %v", err))
return nil
}
return fileBytes
}
func WriteFile(filePath string, contents []byte, mode os.FileMode) error {
return ioutil.WriteFile(filePath, contents, mode)
}
func MustWriteFile(filePath string, contents []byte, mode os.FileMode) {
err := WriteFile(filePath, contents, mode)
if err != nil {
Exit(Fmt("MustWriteFile failed: %v", err))
}
}
// WriteFileAtomic creates a temporary file with data and the perm given and
// swaps it atomically with filename if successful.
func WriteFileAtomic(filename string, data []byte, perm os.FileMode) error {
var (
dir = filepath.Dir(filename)
tempFile = filepath.Join(dir, "write-file-atomic-"+RandStr(32))
// Override in case it does exist, create in case it doesn't and force kernel
// flush, which still leaves the potential of lingering disk cache.
flag = os.O_WRONLY | os.O_CREATE | os.O_SYNC | os.O_TRUNC
)
f, err := os.OpenFile(tempFile, flag, perm)
if err != nil {
return err
}
// Clean up in any case. Defer stacking order is last-in-first-out.
defer os.Remove(f.Name())
defer f.Close()
if n, err := f.Write(data); err != nil {
return err
} else if n < len(data) {
return io.ErrShortWrite
}
// Close the file before renaming it, otherwise it will cause "The process
// cannot access the file because it is being used by another process." on windows.
f.Close()
return os.Rename(f.Name(), filename)
}
//--------------------------------------------------------------------------------
func Tempfile(prefix string) (*os.File, string) {
file, err := ioutil.TempFile("", prefix)
if err != nil {
PanicCrisis(err)
}
return file, file.Name()
}
func Tempdir(prefix string) (*os.File, string) {
tempDir := os.TempDir() + "/" + prefix + RandStr(12)
err := EnsureDir(tempDir, 0700)
if err != nil {
panic(Fmt("Error creating temp dir: %v", err))
}
dir, err := os.Open(tempDir)
if err != nil {
panic(Fmt("Error opening temp dir: %v", err))
}
return dir, tempDir
}
//--------------------------------------------------------------------------------
func Prompt(prompt string, defaultValue string) (string, error) {
fmt.Print(prompt)
reader := bufio.NewReader(os.Stdin)
line, err := reader.ReadString('\n')
if err != nil {
return defaultValue, err
}
line = strings.TrimSpace(line)
if line == "" {
return defaultValue, nil
}
return line, nil
}