Search code examples
pythonpermissionsstatoctal

Using Python's stat function to efficiently get owner, group and other permissions

Question:

How do I efficiently use the stat function to get meaningful file permissions (User, Group and Other).

Details:

I am querying the file permissions like so:

statInfo = os.stat
permissions = stat.S_IMODE ( os.stat ( 'fooBar.txt' ).st_mode )

This returns the permissions in decimal form. So if fooBar.txt has the octal file permissions 0700, here permissions is set to the decimal value448. What I want is to set 9 variables for each permission (ownerRead, ownerWright, ownerExecute, groupRead,...) If I was going to do this, I'd use a brute force method like so:

statInfo = os.stat
permissions = stat.S_IMODE ( os.stat ( 'fooBar.txt' ).st_mode )
octPermissions = oct ( permissions )

ownerRead = octPermissions [1] >= 4
ownerWrite = octPermissions [1] == 2 or octPermissions [1] == 6 or octPermissions [1] == 3 or 
ownerExecute = octPermissions [1] == 1 or octPermissions [1] == 5 or octPermissions [1] == 3

Is there a more efficient way to do this without having to convert to octal as this function will get called quite a bit?

Solution

  • You could use the bitwise AND operator:

    m = os.stat('fooBar.txt').st_mode
otherExec  = bool(m & 0001)
otherWrite = bool(m & 0002)
otherRead  = bool(m & 0004)
groupExec  = bool(m & 0010)
groupWrite = bool(m & 0020)
groupRead  = bool(m & 0040)
...