\( and \) metacharacters are used to delimit
subexpressions.
When the regular expression matches a particular chunk of text,
Elvis will remember which portion of that chunk matched the subexpression.
The :s/regexp/newtext/ command makes use of this feature.
^ metacharacter matches the beginning of a line.
If, for example, you wanted to find "foo" at the beginning of a line,
you would use a regular expression such as /^foo/.
Note that ^ is only a metacharacter if it occurs
at the beginning of a regular expression;
practically anyplace else, it is treated as a normal character.
(Exception: It also has a special meaning inside a [character-list]
metacharacter, as described below.)
$ metacharacter matches the end of a line.
It is only a metacharacter when it occurs at the end of a regular expression;
elsewhere, it is treated as a normal character.
For example, the regular expression /$$/ will search for a dollar sign at
the end of a line.
:set w="[[:alnum:]_:']"
...the command /$w/ will search for the next
letter, digit, underscore, colon, or apostrophe.
Note: This only works if the magicname option is set.
\< metacharacter matches a zero-length string at the
beginning of a word.
A word is considered to be a string of 1 or more letters, digits, or
underscores.
A word can begin at the beginning of a line
or after 1 or more non-alphanumeric characters.
\> metacharacter matches a zero-length string at the end
of a word.
A word can end at the end of the line
or before 1 or more non-alphanumeric characters.
For example, /\<end\>/ would find any instance of the word "end",
but would ignore any instances of e-n-d inside another word
such as "calendar".
\h metacharacter matches a zero-length string at either end
of a word.
The \H metacharacter matches a zero-length string which is
not at either end of a word; it can be either in the middle of a
word, or between words.
The \b and \B metacharacters are the same as
\h and \H, but only if the
magicperl option is set.
Otherwise \b is treated as a backspace.
\@ matches the
word at the cursor.
\= metacharacter, then it
will leave the cursor at the position that matched the \=.
For example, if you place \= at the end of your regular expression,
then the cursor will be left after the matching text instead of at the start
of it.
. metacharacter matches any single character.
NOTE: If the magic option is turned off,
then . is treated as an ordinary, literal character.
You should use \. to get the meta-character version in this case.
^ character,
then the list is inverted -- it will match any character that isn't
mentioned in the list.
For example, /[a-zA-Z]/ matches any ASCII letter, and
/[^ ]/ matches anything other than a blank.
NOTE: If the magic option is turned off, then the opening [ is treated as an ordinary, literal character. To get the meta-character behavior, you should use \[character-list] in this case.
There is no way to quote the ']' or '-' characters, which means that if
you want to include those characters as members of the list, you must place
them in positions where they couldn't be mistaken for the end of the list
or a range.
Specifically, ']' can appear only as the first character in the list
(immediately after the "[" or "[^" that starts the list)
or as the last character in a range.
'-' can appear there too, or immediately after the last character of a range.
For example, [])}] matches a closing bracket, parentheses, or
curly brace.
[^-+] matches any character except '+' or '-'.
Probably the trickiest example, []-]-] matches a closing
bracket or a '-'. (Note that the range "]-]" matches a single bracket;
we wrote it this way so that the following "-" would be in a context where
it couldn't be mistaken for a range and so must be a literal '-' character.)
There are also special cases for some common character lists.
When one of the following special symbols appears in a character list,
the list will include all appropriate characters for that symbol
including the non-ascii characters as indicated by the
digraph table.
Note that the brackets around these symbols are in addition to the brackets
around the whole class.
For example, /[[:alpha:]]/ matches any single letter, and
/[[:alpha:]_][[:alnum:]_]*/ matches any C identifier.
.----------------.-------------------------------------------.
| SPECIAL SYMBOL | INCLUDED CHARACTERS |
|----------------|-------------------------------------------|
| [:alnum:] | all letters and digits |
| [:alpha:] | all letters |
| [:ascii:] | all ASCII characters |
| [:blank:] | the space and tab characters |
| [:cntrl:] | ASCII control characters |
| [:digit:] | all digits |
| [:graph:] | all printable characters excluding space |
| [:lower:] | all lowercase letters |
| [:print:] | all printable characters including space |
| [:punct:] | all punctuation characters |
| [:space:] | all whitespace characters except linefeed |
| [:upper:] | all uppercase characters |
| [:xdigit:] | all hexadecimal digits |
^----------------^-------------------------------------------^
\s, \d, \w, and
\p symbols match (respectively) any whitespace character,
digit, alphanumeric character, or any printable character.
The uppercase versions are the opposites; they match any single character
that the lowercase versions don't match.
\I is any character which can appear appear at the
front of an identifier, and \i is any character which can
appear later in the identifier.
As presently implemented, these character lists are hardcoded to use character
lists that are useful for C/C++, however I expect to make them sensitive the
startword and
inword lines in the
elvis.syn file eventually.
\n.
The \{n\} or \{n} closure operator, in particular, means
that the preceding expression should be repeated exactly n times.
For example, /^-\{80\}$/ matches a line of eighty hyphens, and
/\<[[:alpha:]]\{4}\>/ matches any four-letter word.
/"[^"]\{3,5\}"/ matches any pair of quotes which
contains three, four, or five non-quote characters.
/.\{81,}/ matches any line which contains more than 80 characters.
/.*/ matches a whole line.
NOTE: If the magic option is turned off, then * is treated as an ordinary, literal character. You should use \* to get the meta-character version in this case.
/.\+/ matches a whole line,
but only if the line contains at least one character.
It doesn't match empty lines.
/no[ -]\?one/ matches "no one", "no-one", or "noone".
Anything else is treated as a normal character which must exactly match a character from the scanned text. The special strings may all be preceded by a backslash to force them to be treated normally.
Normally, the closure operators
(\{m,n},
*, \+, and \?) are "greedy",
meaning they try to match as much text as possible.
You can convert any of them into a "non-greedy" version (matching as few
as possible) by placing an extra \? metacharacter after the
closure operator.
For example, in the text "one2three4five6seven8nine", the greedy regular
expression /\d.*\d/ matches "2three4five6seven8", while the
non-greedy /\d.*\?\d/ matches just "2three4".
You can use any punctuation character to delimit the regular expression and the replacement text. The first character after the command name is used as the delimiter. Most folks prefer to use a slash character most of the time, but if either the regular expression or the replacement text uses a lot of slashes, then some other punctuation character may be more convenient.
Most other characters in the substitution string are copied into the text literally but a few have special meaning:
.-------.----------------------------------------------------------.
|SYMBOL | MEANING |
|-------|----------------------------------------------------------|
| ^M | Insert a newline (instead of a carriage-return) |
| & | Insert a copy of the original text |
| ~ | Insert a copy of the previous replacement text |
| \1 | Insert a copy of that portion of the original text which |
| | matched the first set of \( \) parentheses |
| \2-\9 | Do the same for the second (etc.) pair of \( \) |
| \U | Convert following characters to uppercase |
| \L | Convert following characters to lowercase |
| \E | End the effect of \U or \L |
| \u | Convert the next character to uppercase |
| \l | Convert the next character to lowercase |
| \# | Insert the line number, as a string of digits |
| \0 | Insert a nul character |
| \a | Insert a bell character |
| \b | Insert a backspace character |
| \f | Insert a form-feed character |
| \n | Insert a line-feed character |
| \r | Insert a carriage-return character |
| \t | Insert a tab character |
| $name | Value of name option (only if magicname is set) |
|${name}| Alternative form of $name |
^-------^----------------------------------------------------------^
These may be preceded by a backslash to force them to be treated normally.
The delimiting character can also be preceded by a backslash to include
it in either the regular expression or the substitution string.
Traditionally \0 was a synonym for the &
symbol -- they both inserted a copy of the matching text.
Elvis breaks from tradition here to make \0 insert a NUL
character because there would otherwise be no way to have a substitution
insert a NUL character.
The first option is called "[no]magic".
This is a boolean option, and it is "magic" (TRUE) by default.
It selects between two different notations for metacharacters in a regular
expression.
While in nomagic mode, all of the metacharacters except
^ and $ loose their special meaning unless they're
prefixed with a backslash.
In the normal magic mode, metacharacters listed in the
magicchar option's value don't require
a leading backslash but all others do.
The "magicchar" option is intended to allow you to alter Elvis' regular expression syntax to mimic that of other utilities. Vi is a very old editor, and its regular expression syntax is rather archaic.
The "[no]magicperl" option changes
the meanings of some metacharacters to be more Perl-like.
Specifically, it causes \b to mean "edge of a word" instead of
"backspace".
In later versions of Elvis, this is expected to change other metacharacters
as well.
The "[no]magicname" option enables or
disables the use of $name in regular expressions.
Normally it is disabled, so you can search for dollar signs easily.
Aliases will often use ":local
magicname" and then compute and use
a regular expression.
Here's a simple example showing how this might be used:
alias findup {
" Search for uppercase version of current word
local magicname n
let n = toupper(current("word"))
/$n/
}
The "[no]ignorecase"
and "[no]smartcase" options
control whether searches and substitutions will distinguish between
uppercase and lowercase letters.
These are both Boolean options, and both are false by default which
causes all searches to be case sensitive.
Setting ignorecase (while leaving smartcase unset)
causes all searches to be case insensitive, except in a
character list metacharacter.
Setting both ignorecase and smartcase will cause
searches to be case insensitive unless the search expression contains some
uppercase letters, in which case the search will be case sensitive.
Also, the "[no]wrapscan" and "[no]autoselect" options affect searches.
:%s/utilize/use/gThis example deletes all whitespace that occurs at the end of a line anywhere in the file.
:%s/\s\+$//This example converts the current line to uppercase:
:s/.*/\U&/This example underlines each letter in the current line, by changing it into an "underscore backspace letter" sequence. (The ^H is entered as "control-V backspace".):
:s/[a-zA-Z]/_^H&/gThis example locates the last colon in a line, and swaps the text before the colon with the text after the colon. The first \( \) pair is used to delimit the stuff before the colon, and the second pair delimit the stuff after. In the substitution text, \1 and \2 are given in reverse order to perform the swap:
:s/\(.*\):\(.*\)/\2:\1/