Custom Completers Completion Functions
In order to complete some text, the full list of possible completions must be available. That is, it is not possible to accurately expand a partial word without knowing all of the possible words which make sense in that context. The Readline library provides the user interface to completion, and two of the most common completion functions: filename and username. For completing other types of text, you must write your own completion function. This section describes exactly what such functions must do, and provides an example.
There are three major functions used to perform completion:
rl_complete (). This function is called with the same arguments as other Readline functions intended for interactive use: count and invoking_key. It isolates the word to be completed and calls
completion_matches ()to generate a list of possible completions. It then either lists the possible completions, inserts the possible completions, or actually performs the completion, depending on which behavior is desired.
completion_matches ()uses your generator function to generate the list of possible matches, and then returns the array of these matches. You should place the address of your generator function in
completion_matches (), returning a string each time. The arguments to the generator function are text and state. text is the partial word to be completed. state is zero the first time the function is called, allowing the generator to perform any necessary initialization, and a positive non-zero integer for each subsequent call. When the generator function returns
(char *)NULLthis signals
completion_matches ()that there are no more possibilities left. Usually the generator function computes the list of possible completions when state is zero, and returns them one at a time on subsequent calls. Each string the generator function returns as a match must be allocated with
malloc(); Readline frees the strings when it has finished with them.
completion_matches ()). The default is to do filename completion.
completion_matches (). If the value of
(Function *)NULLthen the default filename generator function,
filename_completion_function (), is used.