How to remove an entire line which matches a pattern - regex

The following pattern matches an entire line, how do I search and remove these lines. If I leave a space in the replace string, it leaves a blank in that particular line, when I do via eclipse.
^[\t ]*<param name="logic" .*$

I don't know anything about eclipse but you may need to include the \n newline match in order to remove the line completely. Also - is it possible to replace with an empty string as opposed to a space?
^[\t ]*<param name="logic" .*\n$

To delete the line, you must also remove the line-break, not only the contents of the line.
So your Expression should end with \r\n instead of $.
Can't try it at the moment, so you will have to experiment yourself for the correct syntax.

Related

Regex in "Find and Replace"; how to match \n (newline character)?

I'm not sure whether I couldn't find the correct way or this is a bug.
I wanted to check some reference manual but there doesn't seem to be one.
In Jupyter's Find and Replace screen, there's an icon .* to check when I want to use regex.
Mostly it works fine, but if I try to match a line break (\n), it does not match it unless it is that very character. For example, I want to match every line that doesn't end with , and join that line to the next one. I'd match [^,]\n and replace with ,, which would remove the line break. I could try [^,]$, but replacing this wouldn't remove the line break.
How do I do this?
There are a lot of variants of the new-line character.
E.g.: \r or \n
Regex Pattern
Anyway, here is the pattern using lookahead to check if there is a comma before, and the variants of new-line character.
(?<!,)(\r?(\n|\r))
Regex Demo

Regular expressions: inserting a word and NOT replacing the found key

I have a list of items, such as:
this_thing.ety
other-stuff.ety
34-pairings.ety
I want to do this:
"At the beginning of every line, insert "images/"
so the result of search/replace with reg exp would yield:
images/this_thing.ety
images/other-stuff.ety
images/34-pairings.ety
I am using:
^.
as my anchor to find the beginning of each line but everything I've tried to add "images/" has resulted in actually replacing that first character. I am using Notepad ++, but can use anything.
I thought using ${foo} was on the right track but I'm missing something here.
In a regex ^.is matching begin of line and a character. If you replace this by 'image', first character, which matched, will be replaced. Empty line wont have 'image' but stay identical (they don't match ^.)
Just use ^ as regexp for begin of line
. is the any character symbol, but can only account for one character. You will want to use ^..*$ or ^.+$ if your version of regex allows so that every line that contains at least one character will be fully replaced. With replace, it would look like this
s/^(.+)$/images\/\1/
where the \1 re-inserts the part in parenthesis in the regex. In older versions of regex, try
s/^^\(..*\)$/\1/

Notepad++ regex -> newLine

I use Notepad++ and I need to delete all lines starting with, say "abc".
Attention, I don't need to replace the line starting with "abc" with a empty line, but I need to completely delete these lines.
How do I proceed (using regex, I suppose)?
Try replace
^abc.*(\r?\n)?
with
nothing
The ^ indicates the start of a line.
The . means wild-card.
The .* means zero or more wild-cards.
x? means x is optional.
The \r?\n covers both \r\n (generally Windows) and \n (generally Unix), but must be optional to cover the last line.
Search for this regular expression
^abc.*\r\n
Replace with nothing.
Searching a little bit more on regex in Notepad++ I discovered that the new line character is not \n as I expected (Windows), but the \n\r.
So, my regex replace expression should be:
Find: abc.*\r\n
Replace with: (nothing, empty field)
Try the regex \nabc.* in "Find and Replace" --> "Replace"
Leave "Replace With" field empty.
EDIT : This won't work with first like (because '\n' means "new line")
Press Ctrl+H to bring up the Replace window. Put
^abc.*(\r?\n)?
in the Find what and leave Replace with empty. Select Reqular expression and hit Replace All.
This reqular expression handles all the edge cases:
When the first line of the file starts with abc
When the last line of the file starts with abc and there is no new line at the end of the file.

regex in Notepad++ to remove blank lines

I have multiple html files and some of them have some blank lines, I need a regex to remove all blank lines and leave only one blank line.. So it removes anything more than one blank line, and leave those that are just one or none (none like in having text in them).
I need it also to consider lines that are not totally blank, as some lines could have spaces or tabs (characters that doesn't show), so I need it to consider these lines with the regex to be removed as long as it is more than one line..
Search for
^([ \t]*)\r?\n\s+$
and replace with
\1
Explanation:
^ # Start of line
([ \t]*) # Match any number of spaces or tabs, capture them in group 1
\r?\n # Match one linebreak
\s+ # Match any following whitespace
$ # until the last possible end of line.
\1 will then contain the first line of whitespace characters, so when you use that as the replacement string, only the first line of whitespace will be preserved (excluding the linebreak at the end).
This worked for me on notepad++ v6.5.1. UNICODE windows 7
Search for: ^[ \t]*\r\n
Replace with: nothing, leave blank
Search mode: Regular expression.
search for (\r?\n(\t| )*){3,}, replace by \r\n\r\n, check "Regular expression" and ". matches newline".
Tested with Notepad++ 6.2
This will replace the successive blank lines containing white spaces (or not) and replace it with one new line.
Search for
(\s*\r?\n){3,}
replace with
\r\n
You can find it yourself what you need to replace with
\n\n OR \n\r\n or \r\n\r\n etc ... now you can even modify your regular expression ^([ \t]*)\r?\n\s+$ according to your need.
I tested any of the above suggestions, always was either too less or to much deleted. So that either you got no blank line where at least one was beforehand or deleted not enough (whitespaces was left, etc.). Unfortunately I cannot write comments yet. Tested both with 6.1.5 and updated to 6.2 and tested again. depending on how mayn files there are, I would suggest use
Edit->Blank Operations->Trim trailing whitespace
Followed by Ctrl+A and
TextFX -> TextFX Edit -> Delete surplus blank lines
A Macro I tried to record didn't work. Theres even a macro for just remove trailing whitespace (Alt+Shift+S, see Settings | Shortcut Mapper... | Macros). There's a
Edit->Blank Operations->Remove unnecessary EOL and whitespace
but that deletes every EOL and puts everything in a single line.
In notepad++ v8.4.7 there is the option:
Edit > Line Operations > Remove Empty Lines (Containing Blank characters)
or
Edit > Line Operations > Remove Empty Lines
So there is no need to use a regular expressions for this. But this only works for one file at a time.
I looked for ^\r\n and click "Replace All" with nothing (empty) in "Replace with" textbox.

How to check if a line is blank using regex

I am trying to make simple regex that will check if a line is blank or not.
Case;
" some" // not blank
" " //blank
"" // blank
The pattern you want is something like this in multiline mode:
^\s*$
Explanation:
^ is the beginning of string anchor.
$ is the end of string anchor.
\s is the whitespace character class.
* is zero-or-more repetition of.
In multiline mode, ^ and $ also match the beginning and end of the line.
References:
regular-expressions.info/Anchors, Character Classes, and Repetition.
A non-regex alternative:
You can also check if a given string line is "blank" (i.e. containing only whitespaces) by trim()-ing it, then checking if the resulting string isEmpty().
In Java, this would be something like this:
if (line.trim().isEmpty()) {
// line is "blank"
}
The regex solution can also be simplified without anchors (because of how matches is defined in Java) as follows:
if (line.matches("\\s*")) {
// line is "blank"
}
API references
String String.trim()
Returns a copy of the string, with leading and trailing whitespace omitted.
boolean String.isEmpty()
Returns true if, and only if, length() is 0.
boolean String.matches(String regex)
Tells whether or not this (entire) string matches the given regular expression.
Actually in multiline mode a more correct answer is this:
/((\r\n|\n|\r)$)|(^(\r\n|\n|\r))|^\s*$/gm
The accepted answer: ^\s*$ does not match a scenario when the last line is blank (in multiline mode).
Try this:
^\s*$
Full credit to bchr02 for this answer. However, I had to modify it a bit to catch the scenario for lines that have */ (end of comment) followed by an empty line. The regex was matching the non empty line with */.
New: (^(\r\n|\n|\r)$)|(^(\r\n|\n|\r))|^\s*$/gm
All I did is add ^ as second character to signify the start of line.
The most portable regex would be ^[ \t\n]*$ to match an empty string (note that you would need to replace \t and \n with tab and newline accordingly) and [^ \n\t] to match a non-whitespace string.
Here Blank mean what you are meaning.
A line contains full of whitespaces or a line contains nothing.
If you want to match a line which contains nothing then use '/^$/'.
Somehow none of the answers from here worked for me when I had strings which were filled just with spaces and occasionally strings having no content (just the line terminator), so I used this instead:
if (str.trim().isEmpty()) {
doSomethingWhenWhiteSpace();
}
Well...I tinkered around (using notepadd++) and this is the solution I found
\n\s
\n for end of line (where you start matching) -- the caret would not be of help in my case as the beginning of the row is a string
\s takes any space till the next string
hope it helps
This regex will delete all empty spaces (blank) and empty lines and empty tabs from file
\n\s*