Questions tagged [regular-expressions]
is for patterns specifying search or replace strings. Also known as `regex` or `regexp`, the patterns describe strings to match when searching or replacing. Emacs provides extensive support for `regex` patterns in many commands. Emacs also provides an interactive expression builder for such patterns.
473
questions
41
votes
2
answers
419k
views
What is the regex to match a newline character?
In Emacs regex, \n doesn't match a new line character \n.
Am I correct that $ matches the position between a new line
character and the character right before the new line character.
e.g. for a ...
- 4,947
36
votes
2
answers
9k
views
Understanding of emacs align-regexp
I've read the Emacs documentation for align-regexp but still have difficulty in understanding how it works. What I'm talking about is its prefixed form C-uM-xalign-regexp, not the simple form M-xalign-...
- 547
33
votes
1
answer
6k
views
Why do regular expressions created with the regex builder use syntax different from the interactive regular expressions?
So, using the regular expression builder (M-x re-builder), finding lines that end in \ takes "\\$", while in search and replace by regex, it only takes "\$". I would have expected the regex builder ...
- 2,161
24
votes
6
answers
9k
views
Get all regexp matches in buffer as a list
On the Code Golf Stack Exchange site today, I found this answer in Clojure to the question "Get all links on a webpage".
(->> (slurp "http://www.stroustrup.com")
(re-seq #"(?:http://)?www(...
- 5,644
20
votes
2
answers
5k
views
support for regex look behind and ahead?
I need to perform regex query replace, such that
foo in foo bar is matched, but foo in foo baz is not. Normally I would use regex look ahead, e.g. foo(?=bar).
However, it seems like Emacs cannot do ...
- 433
19
votes
3
answers
2k
views
Elisp regexps ^ and $ vs ` and '
The manual describes the regexp special characters ^ and $. Like in most regular expression dialects I know, they seem to match the start or end of a string. However, I've also discovered that there ...
- 1,208
18
votes
2
answers
5k
views
Only show lines containing phrase/regex
I would like to see all the lines from the current buffer, that contain some phrase, or match regex.
Example:
My buffer:
dam madam
madam
this is da
m a
dam 1
dam 2
dam pi
dam 321:)
is dam 2?
...
- 1,453
18
votes
2
answers
894
views
How can I test and use a Perl regular expression interactively?
Say I have a buffer with text. I would like to test a regular expression (ideally Perl type) against my buffer and have Emacs highlight the matches on it.
For example, the following regexp (taken ...
- 5,137
16
votes
1
answer
8k
views
how do I quickly remove lines from emacs buffer
In an emacs buffer when editing a file called "log/development.log"
how do I quickly remove all lines containing the word "Render"
- 3,743
16
votes
2
answers
2k
views
Incrementally replace a given string
Let us say I have a text like so below:
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
AC(nn)
Now I want to replace the nn with numbers like so
AC(0)
AC(1)
AC(2)
AC(3)
AC(4)...
- 1,470
16
votes
1
answer
1k
views
How do I create a dynamic regexp with rx?
I want to use rx to create regular expressions with runtime values.
Currently, I'm doing this:
(setq strings '("foo" "bar" "baz"))
(eval `(rx symbol-start (or ,@strings) symbol-end))
However, I'd ...
- 6,860
15
votes
2
answers
623
views
Does elisp have regexp literals?
The sheer number of backslashes my regexps require is pretty crazy. Does elisp have regexp literals, so I can write something like
rx"some\(regexp\)"
instead of
"some\\(regexp\\)"
- 795
13
votes
3
answers
4k
views
Is there an equivalent to sed-style substitution commands from vim?
One of the things I miss from vim is being able to type in a substitution command that will work over multiple lines, for example:
:/begin/,/end/s/foo/bar/g
The above command substitutes "foo" for "...
- 1,465
12
votes
7
answers
2k
views
How can I practice searching and replacing with regular expressions interactively in Emacs?
Searching and replacing using regular expressions is clearly a powerful tool to the Emacs user who can routinely perform these actions. However, as an Emacs (and/or programming) beginner, regular ...
- 745
12
votes
1
answer
5k
views
How to escape regexp special characters in a string?
I'm composing a complex regular expression and the user can supply a part of the expression. However, the user-supplied part should be interpreted literally, i.e. regexp special characters should be ...
- 2,540
11
votes
2
answers
2k
views
Search through the values of all variables in Emacs
I'd like to find which variables contain a certain value.
Is there a way to do a regex search through the values of every variable in Emacs?
- 1,768
11
votes
1
answer
816
views
`looking-back` performance
I have some code using (looking-back … (line-beginning-position)). Doc string of looking-back states that it's better to avoid this function because of slowness. I'm curious will following approach ...
- 615
11
votes
1
answer
4k
views
Evil mode and regular expressions
In Vim, if I want search for all variable names LX where X is a number, I can simply type /L\d. However, this doesn't seem to work with evil.
Is there another syntax for regular expressions in Evil ...
- 213
10
votes
3
answers
3k
views
What's the idiomatic (or best) way to trim surrounding whitespace from a string?
I'm working with strings which may have any number of prefix and suffix spaces, tabs, newlines, etc. Currently I have this:
(replace-regexp-in-string
"^[^[:alnum:]]*\\(.*\\)[^[:alnum:]]*$"
"\\1" ...
- 101
10
votes
1
answer
3k
views
How to search an Arabic word in text without its diacritics/accents?
In Arabic as with some other languages there is what is called diacritics to enhance pronunciation. There is no convention on how many diacritics should be written for a single word. Some use the ...
- 1,759
9
votes
1
answer
1k
views
Regex match literal string
I want to write a function (or use an existing one) that will take any string and produce a correctly escaped Regex that matches only that string. What is the fastest and simplest way of doing this?
- 10.2k
9
votes
1
answer
1k
views
Align vertical columns of numbers on the decimal point
I wrote this post in Emacs. In order to make the tables look nice, I decided to adjust the spacing so that decimals line up neatly. The original format from the database looked like this:
emacs ...
- 271
9
votes
1
answer
2k
views
How to match symbol in regexp?
I'm trying to construct a regular expression that would match symbols, that
is, things like function names and the like, according to current major mode
settings (it's called syntax table if I ...
- 4,893
8
votes
1
answer
830
views
How to apply arithmetic operators to query-replace-regex
I am attempting to replace all "begin" and "dur" attribute values in my SVG code with one-tenth of (or ten times) their current values, in order to speed up/slow down animation for testing/debugging ...
- 183
8
votes
1
answer
1k
views
What does a backslash followed by a single quote mean in a regular expression?
Looking at this stackoverflow answer on an old way for specifying the org-file-apps list, I can see that there is a backslash followed by a single-quote character after each file type extension, e.g. ....
- 719
8
votes
3
answers
837
views
Search and replace through a multifile project in AUCTeX?
I am about to adopt Emacs to be the only editor I use in all what I am writing including LaTeX documents. I came from WYSIWYG editor which served that purpose fairly nice, namely TexStudio or TXS for ...
- 1,759
8
votes
1
answer
396
views
Most performant matching of "any char"
On https://www.emacswiki.org/emacs/MultilineRegexp one finds the hint to use
[\0-\377[:nonascii:]]*\n
instead of the standard
.*\n
to match any character up to a newline to avoid stack ...
- 205
7
votes
1
answer
589
views
Is there any principal difference between "A-Z" and upper?
I just want to make sure I understood this correctly.
(rx (one-or-more (any upper lower)))
is equal to
(rx (one-or-more (any "A-Z" "a-z")))
Correct?
- 272
7
votes
3
answers
2k
views
How to grep marked files in the dired mode of emacs?
I hope it's a simple problem..
I'd like to search for the regexp 'thisWord' only in the marked files of a dired buffer.
Usually I used in the dired buffer:
M-x grep and then in the mini-buffer
grep ...
- 346
7
votes
3
answers
31k
views
How to make a dot match a newline
Often I need to use regular expressions to match strings across multiple lines. In python and other languages, it's possible to ask that dots match newlines (as opposed to the default behavior). Is it ...
- 833
7
votes
2
answers
359
views
When to use normal incremental search in place of the regex version?
Assuming familiarity with regex, is there ever any reason to use the normal incremental search (C-s) over regex (C-M-s)?
- 307
7
votes
2
answers
538
views
How to transpose two arguments of a function call for C family languages?
How to swap two arguments for C function calls? eg:
my_function(foo, bar, baz);
~~~~~~~~~~~~~^ (cursor location)
Should be transposed to the right to make:
my_function(bar, foo, baz);
The simple ...
- 8,209
7
votes
1
answer
442
views
Using the count of coincidence from a regexp as replacement text?
I have an org-mode file with more than 12000 footnotes (maybe less), I was cleaning it and found that after the conversion some footnotes weren't converted to org-mode footnotes, so I had to manually ...
- 2,692
7
votes
1
answer
3k
views
In regular expressions, what's the difference between [:blank:], [:space:], and \s-?
I've been playing around with rx lately, and I just noticed there are (at least) 3 different ways of indicating whitespaces in regular expressions.
[:blank:]
[:space:]
\s-
What are the differences ...
- 22.8k
6
votes
3
answers
976
views
Regexp replace to match a string, but not match a superstring
Let's say I want to replace the string "Vector" by "VectorBase", but there are existing instances of "VectorBase". So I would like to omit "VectorBase". What is an elegant way to achieve this?
An ...
- 429
6
votes
3
answers
907
views
highlight-regexp in multiple buffers
highlight-regexp is pretty amazing, but when I run it manually by M-x highlight-regexp RET f?o RET 'someface it only applies the highlight to the current buffer. How can I apply a highlight to ...
- 235
6
votes
1
answer
1k
views
Regexp replacement: difference between \([[:digit:]]+\) and ([[:digit:]]+)
With M-x replace-regexp, I found that both \([[:digit:]]+\) and ([[:digit:]]+) will match (123), and not one without parentheses, But the first will replace 123 and the second (123). I wonder why the ...
- 4,947
6
votes
3
answers
2k
views
How can I build a regexp insensitive to case?
I have a bunch of keywords:
set
write
quit
which each can be shortened down to one letter:
s se set
w wr wri writ write
q qu qui quit
Further, these keywords are case-insensitive, so the following ...
- 6,801
6
votes
1
answer
2k
views
How to use the regexp for digits with an interactive search?
For example, I have the following content in the buffer:
123
1234
12345
123456
1234567
To match the 4 numbers, I need the regular expression of \d{4}.
I would like to do the same in Emacs, when I ...
- 3,855
6
votes
2
answers
3k
views
Emacs replace-regexp reference the match in the replace argument
Is there an easy way to use replace-regexp to do something like:
XYZ001
XYZ002
XYZ003
to
'XYZ001'
'XYZ002'
'XYZ003'
i.e. replace-regexp XYZ* 'XYZ*'
Is replace-regexp the the wrong tool for the ...
- 163
6
votes
1
answer
947
views
How can I use more than 9 regex capture groups in Emacs Lisp?
I have to do a regexp replacement with more than 9 capture groups. How can I do it?
Here there is my code (with \\10 and \\12 that they do not work as I expected to):
(perform-replace "\\\\href{...
- 419
6
votes
1
answer
336
views
Regexp replace without interaction
Is it possible to replace regex like query-replace-regex without asking for each matching ?
- 383
6
votes
1
answer
61
views
How to check with regular expressions or another way if some package is used in a LaTeX document?
How to check if a specific package is used by a LaTeX document.
For example in the below document (intentionally written in an ugly but technically correct format), the packages fontenc, inputenc, ...
- 7,644
6
votes
1
answer
71
views
Matching categories '\cX' and digit
The regex info material suggests that \\c6 should match digit characters.
In UTF-8 encoded buffers it doesn't; some of the other category letters work as expected (l, |, a).
Shouldn't \\c6* match ...
- 894
6
votes
1
answer
184
views
How can I fontify a symbol by regexp match group (as in a naming convention)?
I want to add better support for expl3 to AUCTeX. I have regular expressions that properly group according to the naming conventions for:
functions (\\(?:__)?[a-z]+_)([a-z_]+)(:[nNpTFwcVvxof]*),
...
- 6,801
5
votes
2
answers
24k
views
Escaping brackets in regexp
I tried these two, but none of them worked.
(if (looking-at "\[") (insert "f"))
(if (looking-at "[") (insert "f"))
How can I escape square brackets in emacs regexp?
- 1,577
5
votes
4
answers
420
views
Is there a way to search/replace with regexps interactively using rx syntax?
I really like rx but I can't use it interactively.
Has someone already tried to extend isearch to support rx syntax?
- 313
5
votes
2
answers
216
views
How to detect if the point is at a closing delimiter?
How to detect if the point is at a closing delimiter?
For example:
in Elisp: )
in LaTeX: }
- 7,644
5
votes
2
answers
5k
views
Matching multiline comments in regex
I'm writing a major mode for a language that uses (* ... *) as comments.
I'm trying to match multi-line comments. e.g.
(*
foo
bar
*)
I was initially doing "(\\*.*\\*)", however, . doesn't match ...
- 53
5
votes
1
answer
1k
views
How to save part of a regular expression during search and replace?
I think the best way to explain what I'm trying to do is using an example. Suppose one would want to replace all underlined words with italic ones in org-mode using a regular expression:
_example_ --&...
- 762