Go file permissions test

by Brandon Dyck brandon@dyck.us

This is an experiment to see how os.Chmod and os.Stat interact on Windows. The program creates a temporary file, then for each possible set of permissions (0–0777), sets those permissions on the file with os.Chmod and checks the resulting permissions with os.Stat.

Usage

go-perm-test <filename>

Inserts the results into an SQLite database called filename. There are four objects in the DB schema: tables named {file,dir}_result_raw(expected INT, actual INT) and views named {file,dir}_result.

The result views breaks down the permissions into separate fields: The raw data are in the expected and actual columns, 3-bit fields are in {expected,actual}_{u,g,o} columns, and 1-bit fields are in {expected,actual}_{u,g,o}{r,w,x} columns.

Findings

Permissions as observed through os.Stat depend entirely upon the owner's write bit set through os.Chmod:

sqlite> select distinct format('%o', actual), expected_uw from dir_result;
20000000555|0
20000000777|1
sqlite> select distinct format('%o', actual), expected_uw from file_result;
444|0
666|1

This obviously isn't an exhaustive treatment of the subject, and I'm not really interested in doing one, but it corraborates Michal Pristas’s findings.