viper: Undo and Backups
2.2 Undo and Backups
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Viper provides multiple undo. The number of undo’s and the size is
limited by the machine. The Viper command ‘u’ does an undo. Undo can
be repeated by typing ‘.’ (a period). Another ‘u’ will undo the undo,
and further ‘.’ will repeat it. Typing ‘u’ does the first undo, and
changes the direction.
Since the undo size is limited, Viper can create backup files and
auto-save files. It will normally do this automatically. It is
possible to have numbered backups, etc. For details, 
Backup and
Auto-Save (emacs)Backup.
The results of the 9 previous changes are available in the 9 numeric
registers, as in Vi. The extra goody is the ability to _view_ these
registers, in addition to being able to access them through ‘p’ and
‘M-y’ (Insert State, for details.) The Viper command ‘]
register’ will display the contents of any register, numeric or
alphabetical. The related command ‘[ textmarker’ will show the text
around the textmarker. ‘register’ and ‘textmarker’ can be any letters
from a through z.
Info Catalog
viper: Basics
viper: Improvements over Vi
viper: History