The format of symbolic modes is actually more complex than described above (see Setting Permissions). It provides two ways to make multiple changes to files' permissions.
The first way is to specify multiple operation and permissions parts after a users part in the symbolic mode.
For example, the mode:
og+rX-w
gives users other than the owner of the file read permission and, if it is a directory or if someone already had execute permission to it, gives them execute permission; and it also denies them write permission to it file. It does not affect the permission that the owner of the file has for it. The above mode is equivalent to the two modes:
og+rX
og-w
The second way to make multiple changes is to specify more than one simple symbolic mode, separated by commas. For example, the mode:
a+r,go-w
gives everyone permission to read the file and removes write permission on it for all users except its owner. Another example:
u=rwx,g=rx,o=
sets all of the non-special permissions for the file explicitly. (It gives users who are not in the file's group no permission at all for it.)
The two methods can be combined. The mode:
a+r,g+x-w
gives all users permission to read the file, and gives users who are in the file's group permission to execute it, as well, but not permission to write to it. The above mode could be written in several different ways; another is:
u+r,g+rx,o+r,g-w