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// +build !windows
package singleinstance
import (
"os"
"strconv"
"syscall"
)
// CreateLockFile tries to create a file with given name and acquire an
// exclusive lock on it. If the file already exists AND is still locked, it will
// fail.
func CreateLockFile(filename string) (*os.File, error) {
file, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE, 0600)
if err != nil {
return nil, err
}
err = syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
if err != nil {
file.Close()
return nil, err
}
// Write PID to lock file
contents := strconv.Itoa(os.Getpid())
if err := file.Truncate(0); err != nil {
file.Close()
return nil, err
}
if _, err := file.WriteString(contents); err != nil {
file.Close()
return nil, err
}
return file, nil
}
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