If no name s are specified then variables that have the specified options are displayed. If the first option is specified with a leading - then the name and value of each variable is written to standard output. Otherwise, only the names are written. If no options are specified or just -p is specified, then the names and attributes of all variables are written to standard output. When -f is specified, the names displayed will be function names.
Tilde expansion occurs on value .
Each of the options and name s refers to a function. The option value may be omitted. The default value is 10 . Unsets -u attribute. The value is the name of a variable that name references.