How to Achieve Exclusive File Access in Go?

Locking a File Exclusively in Go

Question: How can I obtain exclusive read access to a file in Go, preventing other processes from accessing it while it remains open?

Answer:

Cross-Platform Solution Using fslock

To achieve exclusive file access in Go, we can utilize the fslock package from GitHub: https://github.com/juju/fslock. This package provides a cross-platform locking mechanism based on file locks.

Steps:

1. Create a Lock Object:
   Initialize a Lock object for the target file:

   lock := fslock.New("file.txt")

2. Lock the File:
   To obtain the lock, use the Lock() method:

   lockErr := lock.Lock()

3. Handle Errors:
   If the lock cannot be acquired, handle the error:

   if lockErr != nil {
       log.Fatal(lockErr)
   }

4. Release the Lock:
   Once the file operation is complete, release the lock:

   lock.Unlock()

5. Timeout Option:
   If immediate locking is not critical, use the LockWithTimeout() method to specify a timeout duration:

   lockErr := lock.LockWithTimeout(30 * time.Second)

Example Implementation:

package main

import (
    "fmt"
    "github.com/juju/fslock"
    "time"
)

func main() {
    lock := fslock.New("lock.txt")
    lockErr := lock.TryLock()
    if lockErr != nil {
        fmt.Println("failed to acquire lock >", lockErr.Error())
        return
    }

    fmt.Println("got the lock")
    time.Sleep(1 * time.Minute)

    // release the lock
    lock.Unlock()
}

Using fslock, you can effectively control access to a file in Go, ensuring exclusive read operations and denying write access to any other processes until the lock is released.

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