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Chapter 9: Variables 59exist (name, type)Built-in FunctionReturn 1 if the name exists as a variable, 2 if the name (after appending ‘.m’) isa function file in Octave’s LOADPATH, 3 if the name is a ‘.oct’ file in Octave’sLOADPATH, 5 if the name is a built-in function, 7 if the name is a directory, 101 ifthe name is a built-in variable, 102 if the name is a built-in constant, or 103 if thename is a function not associated with a file (entered on the command line).Otherwise, return 0.This function also returns 2 if a regular file called name exists in Octave’s LOADPATH.If you want information about other types of files, you should use some combinationof the functions file_in_path and stat instead.If the optional argument type is supplied, check only for symbols of the specified type.Valid types are‘"var"’Check only for variables.‘"builtin"’Check only for built-in functions.‘"file"’‘"dir"’Check only for files.Check only for directories.document (symbol, text)Set the documentation string for symbol to text.Built-in Functiontype options name . . .Display the definition of each name that refers to a function.CommandNormally also displays if each name is user-defined or builtin; the -q option suppressesthis behaviour.Currently, Octave can only display functions that can be compiled cleanly, because ituses its internal representation of the function to recreate the program text.Comments are not displayed because Octave’s parser currently discards them as itconverts the text of a function file to its internal representation. This problem maybe fixed in a future release.which name . . .CommandDisplay the type of each name. If name is defined from a function file, the full nameof the file is also displayed.9.4 Summary of Built-in VariablesHere is a summary of all of Octave’s built-in variables along with cross references toadditional information and their default values. In the following table octave-home standsfor the root directory where all of Octave is installed (the default is ‘/usr/local’, versionstands for the Octave version number (for example, 2.1.x) and arch stands for the type ofsystem for which Octave was compiled (for example, i586-pc-linux-gnu).