fs.access()

fs.access(path[, mode], callback)

Tests a user's permissions for the file specified by path. mode is an optional integer that specifies the accessibility checks to be performed. The following constants define the possible values of mode. It is possible to create a mask consisting of the bitwise OR of two or more values.

• fs.F_OK - File is visible to the calling process. This is useful for determining if a file exists, but says nothing about rwx permissions. Default if no mode is specified.
• fs.R_OK - File can be read by the calling process.
• fs.W_OK - File can be written by the calling process.
• fs.X_OK - File can be executed by the calling process. This has no effect on Windows (will behave like fs.F_OK).

The final argument, callback, is a callback function that is invoked with a possible error argument. If any of the accessibility checks fail, the error argument will be populated. The following example checks if the file /etc/passwd can be read and written by the current process.

fs.access('/etc/passwd', fs.R_OK | fs.W_OK, (err) => {
  console.log(err ? 'no access!' : 'can read/write');
});