Golang reads whether the file exists

Determining whether a file exists is a very common requirement, and there are many solutions to achieve this function in golang.

Cross-platform implementation

The idea of ​​cross-platform implementation is very simple. If a file does not exist, then using os.Lstat will definitely return an error. Just judge the error It just means that the file does not exist.

Perhaps you have noticed that some codes use os.Open to complete the above work, but it is best not to do this, because although there is no difference in the functions completed by the two, the calling overhead of open and stat is different. The latter is smaller than the former, and for determining whether a file exists, it makes more sense to check its metadata than to directly try to open it.

Then let’s take a look at the implemented code:

func FileExist(path string) bool {
  _, err := os.Lstat(path)  
return !os.IsNotExist(err)
}

POSIX platform implementation

If your program is for POSIX platform (such as UNIX, Linux etc.), then there is a simpler solution - syscall.Access.

syscall.Access provides a means for users to check file metainformation. It is usually used to check file permissions and the existence of files.

Check the file by using the syscall.F_OK flag. If it does not exist, the same error as os.Lstat will be returned:

func FileExist(path string) bool {
  err := syscall.Access(path, syscall.F_OK)
  return !os.IsNotExist(err)
}

The biggest advantage of this implementation is that it is simple and intuitive, but it Not available on Windows.

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