set-permissions

#!/usr/bin/env python3

# Copyright 2018 Joseph Lorimer <joseph@lorimer.me>
#
# Permission to use, copy, modify, and distribute this software for any purpose
# with or without fee is hereby granted, provided that the above copyright
# notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
# OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.

from os import W_OK, access, chmod, stat, walk
from os.path import isfile, islink, join
from shutil import chown

from click import argument, command, option, secho
from magic import from_file as magic


@command()
@argument('perms')
@option('-d', 'start', default='.', help='Root directory to descend into.')
@option('-e', is_flag=True, default=False,
        help='If file is executable, keep owner execute bit.')
def main(perms, start, e):
    """Sets user, group and read-write-execute permissions recursively.
    Permission format is user:group:dirmode:filemode.
    """
    user, group, dmode, fmode = perms.split(':')
    for root, dirs, files in walk(start):
        for d in dirs:
            p = join(root, d)
            if no_access(p):
                continue
            change_owner(p, user, group)
            change_mode(p, dmode)
        for f in files:
            p = join(root, f)
            if no_access(p):
                continue
            if islink(p) and not isfile(p):
                error('broken symbolic link', p)
                continue
            is_exec = magic(p).find('executable') != -1 if e else False
            change_owner(p, user, group)
            change_mode(p, fmode, is_exec)


def no_access(path):
    if not access(path, W_OK):
        warn('no write access', path)
        return True
    return False


def change_owner(path, user, group):
    if user or group:
        try:
            chown(path, user=user, group=group)
        except LookupError:
            error('user or group does not exist')
        except OSError as e:
            warn(e.strerror.lower(), e.filename)


def change_mode(path, new_mode, is_exec=False):
    cur_mode = int(str(oct(stat(path).st_mode))[-3:], 8)
    new_mode = int(new_mode, 8)

    if is_exec:
        exec_set = new_mode & 0o111
        if not exec_set:
            new_mode |= 0o100

    if cur_mode != new_mode:
        secho(
            '{}: {:o} => {:o}'.format(path, cur_mode, new_mode),
            err=True,
            fg='green'
        )
        chmod(path, new_mode)


def error(msg, path=None):
    prefix = '{}: error'.format(path) if path else 'fatal error'
    secho('{}: {}'.format(prefix, msg), err=True, fg='red')
    exit(1)

def warn(msg, path):
    prefix = '{}: warning'.format(path)
    secho('{}: {}'.format(prefix, msg), err=True, fg='yellow')


if __name__ == '__main__':
    main()