Magma provides a history system which allows the recall and editing of previous lines. The history system is invoked by typing commands which begin with the history character `%'. Currently, the following commands are available.

%p

List the contents of the history buffer. Each line is preceded by its history line number.

Reenter the last line into the input stream.

%n

Reenter the line specified by line number n into the input stream.

%n_1 n_2

Reenter the history lines in the range n_1 to n_2 into the input stream.

Edit the last line. The editor is taken to be the value of the EDITOR environment variable if it set, otherwise "/bin/ed" is used. If after the editor has exited the file has not been changed then nothing is done. Otherwise the contents of the new file are reentered into the input stream.

%en

Edit the line specified by line number n.

%en_1 n_2

Edit the history lines in the range n_1 to n_2.

Execute the given command in the Unix shell then return to Magma.