 | Chapter 10 elvis |  |
This section describes the features of elvis that make simple text editing easier and more powerful.
Everything you type on the ex command line is
saved in a buffer named Elvis ex history.
This is accessible like any other elvis buffer,
but is not directly useful when just viewed in a window.
In order to access the history, you use the arrow keys
on your terminal to display previous commands and to edit them.
Use 
and 
to page through the list, and 
and 
to
move around on a command line. You can insert characters by typing
and erase them by backspacing over them.
Much as when editing in a regular vi buffer,
the backspace does remove the characters, but the
line is not updated as you type, so be careful!
When entering text into the Elvis ex history
buffer (i.e., on the colon command line), the [TAB]
key can be used for filename expansion.
The preceding word is assumed to be a partial filename,
and elvis searches
for all matching files.
If there are multiple matches, it fills in as many characters of the
name as possible, and then beeps;
or, if no additional characters are implied by the matching filenames,
elvis lists all matching names and
redisplays the command line.
If there is a single match, elvis
completes the name and appends a tab character.
If there are no matches,
elvis simply inserts a tab character.
To get a real tab character, precede it with a ^V.
You can also disable filename completion entirely by setting the
Elvis ex history buffer's
inputtab
option to tab, via the following command:
:(Elvis ex history)set inputtab=tab
Tag stacking is described in Section 8.5.3, "Tag Stacks" in Chapter 8. In elvis, tag stacking is very straightforward, as shown in Table 10.5 and Table 10.6.
| Command | Function |
|---|---|
ta[g][!] [tagstring] | Edit the file containing
tagstring as defined in the tags
file. The |
stac[k] | |
po[p][!] | Pop a cursor position off the stack, restoring the cursor to its previous position. |
| Command | Function |
|---|---|
^] | Look up the location of the identifier under the cursor in the tags file, and move to that location. The current location is automatically pushed onto the tag stack. |
^T | Return to the previous location in the tag stack, i.e., pop off one element. |
Unlike traditional vi,
when you type ^],
elvis
looks up the entire word
containing the cursor, not just the part of the word from the
cursor location forward.
In HTML mode (discussed in
Section 10.10.1),
the commands all work the same except that :tag expects to
be given a URL instead of a tag name.
URLs don't depend on having a tags file,
so the tags file is ignored
when in HTML mode.
elvis 2.0
doesn't support any network protocols,[3]
so its URLs can only consist
of a file name and/or an HTML #label.
[3] This is no longer true in elvis 2.1; see Section 10.11, "elvis Futures" for details.
Several :set options affect how elvis
works with tags, as described in
Table 10.7.
| Option | Function |
|---|---|
taglength, tl | Control the number of significant characters in a tag that is to be looked up. The default value of zero indicates that all characters are significant. |
tags, tagpath | The value is a list of directory
and/or filenames in which to look for tags files.
elvis looks for a file named tags
in any entry that is a directory.
Entries in the list are colon-separated (or semicolon on DOS/Windows),
in order to allow spaces in directory names.
The default value is just
|
tagstack | When set to true,
elvis stacks each location on the tag stack.
Use |
Version 2.1 of elvis (in beta test as of this
writing) supports the extended tags file
format described earlier. elvis comes with its
own version of ctags. The version in
elvis 2.1 generates the enhanced format described
earlier. Here is an example of the special !_TAG_
lines it produces:
!_TAG_FILE_FORMAT 2 /supported features/ !_TAG_FILE_SORTED 1 /0=unsorted, 1=sorted/ !_TAG_PROGRAM_AUTHOR Steve Kirkendall /[email protected]/ !_TAG_PROGRAM_NAME Elvis Ctags // !_TAG_PROGRAM_URL ftp://ftp.cs.pdx.edu/pub/elvis/README.html // !_TAG_PROGRAM_VERSION 2.1 //
Finally, in elvis, each window has its own tag stack.
With elvis,
before being able to undo and redo multiple levels of changes,
you must first set the undolevels option to
the number of levels of "undo" that elvis
should allow.
A negative value disallows any undoing (which is
not terribly useful).
The elvis documentation warns that each level of undo
uses around 6K bytes of the session file (the file that describes
your editing session), and thus can eat up disk space rather quickly.
It recommends not setting undolevels any
higher than 100 and "probably much lower."
Once you've set undolevels to a non-zero
value, you enter text as normal. Then each successive u
command undoes one change.
To redo (undo the undo), you use the
(rather mnemonic) [CTRL-R] command.
In elvis,
the default value of undolevels
is zero, which causes elvis to
mimic UNIX vi.
The option applies per buffer being edited; see
Section 10.4.2, "Initialization Steps"
for a description
of how to set it for every file that you edit.
Once undolevels has been set, a count to either
the u or ^R commands undoes or
redoes the given number of changes.
elvis can edit files with arbitrary length lines, and with an arbitrary number of lines.
Under UNIX, elvis
does not treat a binary file differently from any other file.
On other systems, it uses the elvis.brf
file to set the binary option.
This avoids newline translation issues.
You can enter eight-bit text by typing ^X
followed by two hexadecimal digits.
Using the hex display mode is an excellent
way to edit binary files.
(The elvis.brf file and the hex
display mode are described in
Section 10.10, "Interesting Features".)
As mentioned in
Section 8.6.4, "Incremental Searching" in Chapter 8,
you enable
left-right scrolling in elvis using
:set nowrap. The value of
sidescroll controls the number of characters
by which elvis shifts the screen when scrolling
left to right.
The ^W S command toggles the value of this option.
elvis allows you to select regions one character at a time, one line at a time, or rectangularly, using the commands shown in Table 10.8.
| Command | Function |
|---|---|
v | |
V | Start region selection, line at a time mode. |
^V |
elvis highlights (using reverse video) the text as you are selecting. To make your selection, simply use the normal motion keys. The screen below shows a rectangular region:
The 6th edition of <citetitle>Learning the vi Editor</citetitle> brings the book into the late 1990’s. In particular, besides the “original” version of <command>vi</command> that comes as a standard part of every UNIX system, there are now a number of freely available “clones” or work-alike editors.
elvis only permits a few operations on selected areas of text. Some operations work only on whole lines, even if you've selected a region that does not contain whole lines (see Table 10.9).
| Command | Operation |
|---|---|
c, d, y | Change, delete, or yank text. Only
|
<, >, ! | Shift text left or right, filter text. These operate on the whole lines containing the marked region. |
After using the d command to delete the
region, the screen now looks like this:
The 6th edition of <citetitle>Learning the vi Editor</citetitle> brings the 90’s. In particulo;original” version of <command>vi as a standard part of every system, there are n available “clones” or work-alike editors.
|  | |
| 10.7 Extended Regular Expressions |  | 10.9 Programming Assistance |
