38
votes
Accepted
Why do regular expressions created with the regex builder use syntax different from the interactive regular expressions?
There are actually four different re-builder syntax options, and you can switch between them with C-cTAB
Two are for the sexp-form regexp compilers rx and sregex (but as the former is more ...
- 44.2k
37
votes
Accepted
Understanding of emacs align-regexp
OK, first the alignments and then the explanation of how it works.
To align the first one, select the lines, do C-u M-x align-regexp and choose: \(\s-*\):, 1, 1, and y.
For the second, use ,\(\), 1, ...
- 583
31
votes
What is the regex to match a newline character?
Yes. $ matches the end of the line, not the newline character which comes after the end of the line.
Do C-M-s C-q C-j. C-q is the default binding for quoted-insert and works in the minibuffer too. ...
- 24.5k
25
votes
Accepted
Only show lines containing phrase/regex
...see all the lines from the current buffer...
With built-in commands and no external packages or dependencies in
a new buffer, use:
M-x occur
the same buffer, use:
M-x keep-lines
- 5,423
23
votes
Accepted
how do I quickly remove lines from emacs buffer
You can go to beginning of buffer with M-<, then M-x flush-lines, type your word and hit RET.
(flush-lines REGEXP &optional RSTART REND INTERACTIVE)
Delete lines containing matches for ...
- 1,270
19
votes
Accepted
Get all regexp matches in buffer as a list
Here is how you can do it based on strings, as requested.
(defun re-seq (regexp string)
"Get a list of all regexp matches in a string"
(save-match-data
(let ((pos 0)
matches)
...
- 817
17
votes
How can I practice searching and replacing with regular expressions interactively in Emacs?
Besides regexp-builder you might also consider visual-regexp to provide you with visual feedback on the replace in progress:
- 524
17
votes
What is the regex to match a newline character?
As Dan comments, the regex that matches a newline is a newline.
You can represent a newline in a quoted string in elisp as "\n". There is no special additional regexp-specific syntax for this -- you ...
- 44.2k
16
votes
How can I practice searching and replacing with regular expressions interactively in Emacs?
You can try M-x regexp-builder RET which is an interactive regular expression matcher, that's not bad
- 541
16
votes
Accepted
How can I test and use a Perl regular expression interactively?
There are two nice packages for working with perl kind of regexes effectively, which should be used together - visual-regexp and it's extension - visual-regexp-steroids. They are great addition to ...
- 506
16
votes
Accepted
How do I create a dynamic regexp with rx?
rx-to-string takes a regexp form as an argument. The syntax is the same as the argument of rx.
(rx-to-string '(or "foo" "bar"))
"\\(?:\\(?:bar\\|foo\\)\\)"
What you tried passing is not a regexp ...
16
votes
Accepted
Elisp regexps ^ and $ vs ` and '
Your string might have an embedded newline character, in which case \' matches the end of the string but $ matches just before the newline char.
To quote the Elisp manual, node Regexp Special:
...
- 70.9k
16
votes
Accepted
Incrementally replace a given string
General technique
Your replacement string can contain arbitrary lisp code. From the documentation for replace-regexp:
In interactive calls, the replacement text may contain ‘\,’ followed by a Lisp ...
- 8,639
15
votes
Accepted
Search through the values of all variables in Emacs
Does apropos-value do what you're looking for?
(apropos-value PATTERN &optional DO-ALL)
Show all symbols whose value’s printed representation matches PATTERN.
PATTERN can be a word, a list of ...
- 461
14
votes
Get all regexp matches in buffer as a list
It's probably worth noting that invoking occur with the universal argument causes it to populate the *Occur* buffer with only matches — no file names, line numbers or header information. When combined ...
- 141
14
votes
Accepted
How to escape regexp special characters in a string?
You can use regexp-quote:
This function returns a regular expression whose only exact match is string. Using this regular expression in looking-at will succeed only if the next characters in the ...
Dan♦
- 31.3k
14
votes
support for regex look behind and ahead?
No, Emacs regular expressions do not support arbitrary zero-width look-ahead/behind assertions.
n.b. Evil and Spacemacs (like all elisp libraries) are irrelevant when it comes to questions about the ...
- 44.2k
13
votes
Accepted
Does elisp have regexp literals?
One option is to use the rx macro to construct your expressions using sexps.
Your example becomes (rx "some" (group "regexp"))
Here are a couple more examples from the commentary section in rx.el, ...
- 19.5k
13
votes
Accepted
Is there any principal difference between "A-Z" and upper?
The macro rx returns regexp strings that can be passed to other Emacs functions.
ELISP> (rx (one-or-more (any upper lower)))
"[[:lower:][:upper:]]+"
ELISP> (rx (one-or-more (any "A-Z" "a-z")))
"...
- 8,639
13
votes
What's the idiomatic (or best) way to trim surrounding whitespace from a string?
What's the idiomatic (or best) way to trim surrounding whitespace from a string?
The built-in library subr-x.el has included the inline functions string-trim-left, string-trim-right, and string-trim ...
- 11.5k
11
votes
Accepted
Regexp replacement: difference between \([[:digit:]]+\) and ([[:digit:]]+)
In emacs regular expressions (unlike most regexp engines), \( and \) are group delimiters, while ( and ) match litteral brackets.
So: \([[:digit:]]+\) matches one digit or more, that is here 123, and ...
- 4,133
11
votes
Accepted
What does a backslash followed by a single quote mean in a regular expression?
It's a special construct in emacs regexp that matches the end of a string (not just the end of a line). Quoting the the manual
\'
matches the empty string, but only at the end of the string or ...
- 1,490
10
votes
Is there an equivalent to sed-style substitution commands from vim?
Here is one way of doing it that uses built-in functionality only:
With point in the line that contains first occurrence of begin, press C-SPC.
Move to next occurrence of end:
C-s end RET
Replace ...
- 14.3k
10
votes
Accepted
How to save part of a regular expression during search and replace?
Use \(...\)for grouping and \1 to reference the first saved group (\2 for the second, all the way up to \9). E.g.:
query-replace-regexp: _\([^_]+\)_ into /\1/.
See Regexp Backslash in the Emacs Lisp ...
- 13.6k
10
votes
Get all regexp matches in buffer as a list
I have an emacs lisp answer to that question posted: https://codegolf.stackexchange.com/a/44319/18848
Using the same (while (search) (print)) structure you could modify it into a function to push ...
- 12.2k
10
votes
Accepted
`looking-back` performance
Definitely. You will especially gain if you just want to test char-before or search backward for a literal string. And if you must use looking-back then try to use a LIMIT argument, if possible.
See ...
- 70.9k
10
votes
Is there an equivalent of string-match for regexp?
For the sake of an answer:
string-match is meant for to be used with regexps.
(string-match REGEXP STRING &optional START)
Return index of start of first match for REGEXP in STRING, or ...
- 12.2k
10
votes
Accepted
How to apply arithmetic operators to query-replace-regex
\2 in your replacement is a string, and it needs to be a number in order to perform the division.
You could convert it to a number using string-to-number, but there's in-built shorthand for treating ...
- 4,167
9
votes
Accepted
Regex match literal string
You are looking for regexp-quote:
This function returns a regular expression whose only exact match is string. Using this regular expression in looking-at will succeed only if the next characters ...
Dan♦
- 31.3k
Only top scored, non community-wiki answers of a minimum length are eligible