How to do a multiline search in less?

In less, can you search using / for a pattern that contains a carriage return and newline? I know your pattern can end with a line using $ (from How do I include newlines in a search in less?), but I need the pattern to match text that spans multiple lines.

I tried \n, but that only searches for the n character.

yonran

Posted 2013-01-09T21:16:26.493

Reputation: 482

Which Linux distribution, and do you have defined the environment variable "LESS" ? – harrymc – 2015-02-23T12:59:43.807

@harrymc How would that help with multiline search? – sashoalm – 2015-02-25T18:54:55.130

Gathering information. – harrymc – 2015-02-25T19:29:13.320

I fear the answer for less must be no, but if you are looking for other ways to search this has been discussed here, pcregrep looks the easiest solution.

– gogoud – 2015-02-25T23:05:38.137

2This is not possible, based on a review of the source code for less (search.c:search_range()). The search/match operation is performed on a single newline-delimited line at a time, so you cannot match across line boundaries. See line.c:forw_raw_line() for the implementation of "readline" as called by search_range. – zackse – 2015-02-26T05:50:59.333

Have you tried \n+ for 1 or more newlines? – Brock Hensley – 2014-01-17T01:45:36.793

Answers

It is not possible to match across line boundaries, because the search function in less operates on a single newline-delimited line at a time. This is the case regardless of the system regex implementation (GNU, POSIX, PCRE, etc.).

Please note that I couldn't find an official source repository for the mainline development of less, but for purposes of code review here, the links that follow are from the FreeBSD contrib tree.

See search.c:search_range() for the implementation of the search operation. The loop therein calls line.c:forw_raw_line() to retrieve the next newline-delimited block of content. That block is passed to match.c:match_pattern() where the search pattern (regular expression) is executed.

To match across multiple lines, you'll need to use a different tool. One option is to drop into your editor and use its search capabilities as suggested by others. You can invoke the editor by pressing v in less.

zackse

Posted 2013-01-09T21:16:26.493

Reputation: 532

Not sure how to do it in less, but you can accomplish the same in vim.

http://vim.wikia.com/wiki/Search_across_multiple_lines

/PATTERN1\\_.\\{-}PATTERN2

The atom \\_. finds any character including end-of-line. The multi \\{-} matches as few as possible.

Vam

Posted 2013-01-09T21:16:26.493

Reputation: 29

1This does not answer the question, however, since it is about less, not vim. It should be a comment. – sashoalm – 2015-02-22T06:47:51.797

1@sashoalm It's still an attempt to answer, so I'd vote it down, and move on. People searching for a solution may not be bound to use one tool specifically. – slhck – 2015-02-22T13:50:38.417

less is using ed regex syntax and it does not support multiline matching unfortunately.

https://www.gnu.org/software/gnulib/manual/html_node/ed-regular-expression-syntax.html#ed-regular-expression-syntax

I was hoping to find that as well, or at least find if this syntax bit was used in less:

RE_DOT_NEWLINE If this bit is set, then the match-any-character operator matches a newline; if this bit isn’t set, then it doesn’t.

So I can use .+ pattern to match newlines. But no, it doesn't.

stimur

Posted 2013-01-09T21:16:26.493

Reputation: 121