su
su - user ;entry the user's catalog.
su user ;indicate remain in the current directory.not entry the user's catalog
chown
chown [options] user-owner files
chown [options] user-owner. files
chown [options] user-owner.group-owner files
chown [options].group-owner files
chown [options]--reference=rfile files
description
used to change the owner and/or group of files to user-owner and/or group-owner.in the first form.user-owner is made the owner of files and the group is no affected.in the second form(note the trailing(结尾,尾随的) dot on user-owner),the user-owner is made the owner of files and the group of the files is changed to user-owner's default group.in the third form,both user-owner and group-owner are assigned to files.in the fourth form,only the group-owner is assigned to files,and the user is not affected.in the fifth form,the owner andd group of rfile is used as a template and applied to files.since this program can handle all types of changes to groups, it replaces the chgrp command.only the superuser may change file ownership.but group ownership may be set anyong belonging to the target group-owner. -c like verbose mode.but report only changes -R user recursive mode,descending through directory hierarchies under files and making midifications throughout. -v use verbose behavior,reporting actions for all files for example chown -v jdoe afile chown -Rv .sales sls chgrp change the group parameter of files to group-owner;
