How can I get an exclusive read access to a file in go? I have tried documentations from docs but I am still able to open the file in notepad and edit it. I want to deny any other process to have access to read and write while the first process has not closed it explicitly. In .NET I could do something as:
File.Open("a.txt", FileMode.Open, FileAccess.ReadWrite, FileShare.None);
How do I do it in go?
I finally found a go package that can lock a file.
Here is the repo: https://github.com/juju/fslock
go get -u github.com/juju/fslock
this package does exactly what it says
fslock provides a cross-process mutex based on file locks that works on windows and *nix platforms. fslock relies on LockFileEx on Windows and flock on *nix systems. The timeout feature uses overlapped IO on Windows, but on *nix platforms, timing out requires the use of a goroutine that will run until the lock is acquired, regardless of timeout. If you need to avoid this use of goroutines, poll TryLock in a loop.
To use this package, first, create a new lock for the lockfile
func New(filename string) *Lock
This API will create the lockfile if it already doesn't exist.
Then we can use the lockhandle to lock (or try lock) the file
func (l *Lock) Lock() error
There is also a timeout version of the above function that will try to get the lock of the file until timeout
func (l *Lock) LockWithTimeout(timeout time.Duration) error
Finally, if you are done, release the acquired lock by
func (l *Lock) Unlock() error
Very basic implementation
package main
import (
"time"
"fmt"
"github.com/juju/fslock"
)
func main() {
lock := fslock.New("../lock.txt")
lockErr := lock.TryLock()
if lockErr != nil {
fmt.Println("falied to acquire lock > " + lockErr.Error())
return
}
fmt.Println("got the lock")
time.Sleep(1 * time.Minute)
// release the lock
lock.Unlock()
}
Right now I would recommend go-internal
go get github.com/rogpeppe/go-internal
The reason is, Go does have a lock package but it's internal (we can't use) and go-internal is just providing us the same code as a package.
Also, it uses os.File instead of creating another struct. So it's probably very compatible with others Go codes.
package main
import (
"fmt"
"github.com/rogpeppe/go-internal/lockedfile"
)
func main() {
file, _ := lockedfile.Edit("example.txt") // Write Lock
fmt.Fprintf(file, "%d", 10)
file.Close() // Unlock
}
Negative side, doesn't have "try lock" or timeout.
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