if chmod --version &>/dev/null # gnu's not unix
    complete chmod -s c -l changes -d 'Like -v but report only changes'
    complete chmod -l no-preserve-root -d 'Don\'t treat / special (default)'
    complete chmod -l preserve-root -d 'Fail to operate recursively on /'
    complete chmod -s f -l silent -l quiet -d 'Suppress most errors'
    complete chmod -s v -l verbose -d 'Prints each file processed'
    complete chmod -l reference -d 'Use RFILEs mode instead of MODE values' -r
    complete chmod -s R -l recursive -d 'Operate recursively'
    complete chmod -l help -d 'Display help and exit'
    complete chmod -l version -d 'Display version and exit'
else # guess it might be unix
    complete chmod -s f -d 'Suppress errors'
    complete chmod -s H -d "Follow given symlinks with -R"
    complete chmod -s h -d "Don't dereference given symlinks"
    complete chmod -s L -d "Follow all symlinks with -R"
    complete chmod -s P -d "Follow no symlinks with -R"
    complete chmod -s R -d 'Operate recursively'
    complete chmod -s v -d 'Prints each file processed'
end