List all currently defined symbols. List built-in variables and functions. List user-defined functions. Print a long listing including the type and dimensions of any symbols. The symbols in the first column of output indicate whether it is possible to redefine the symbol, and whether it is possible for it to be cleared.
Valid patterns are the same as described for the clear command above.
If no patterns are supplied, all symbols from the given category are listed. By default, only user defined functions and variables visible in the local scope are displayed. Otherwise, return 0. This is useful for aborting from functions. If msg does not end with a new line character, Octave will print a traceback of all the function calls leading to the error.