How to do a non-greedy match in grep?
regex non greedy
grep lazy match
grep first match
grep show only match
bash regex non greedy
grep capture group
I want to grep the shortest match and the pattern should be something like:
<car ... model=BMW ...> ... ... ... </car>
... means any character and the input is multiple lines.
You're looking for a non-greedy (or lazy) match. To get a non-greedy match in regular expressions you need to use the modifier
? after the quantifier. For example you can change
grep doesn't support non-greedy modifiers, but you can use
grep -P to use the Perl syntax.
You need grep with PCRE (Perl Compatible Regular Expression) support. e.g. GNU grep has this -- can be leveraged with the -P option. There is also a How to do a non-greedy match in grep ? - Wikitechy. HOT QUESTIONS. What is difference between class and interface in C#; Mongoose.js: Find user by username LIKE value
.*? only works in
perl. I am not sure what the equivalent grep extended regexp syntax would be. Fortunately you can use perl syntax with grep so
grep -P would work but
grep -E which is same as
egrep would not work (it would be greedy).
To get a non-greedy match in regular expressions use the modifier ? after the quantifier. For instance we can change .* to .*?. In grep, it does not For non-greedy match in grep you could use a negated character class. In other words, try to avoid wildcards. For example, to fetch all links to jpeg files from the page content, you'd use: grep -o '"[^" ]\+.jpg"'
My grep that works after trying out stuff in this thread:
echo "hi how are you " | grep -shoP ".*? "
Just make sure you append a space to each one of your lines
(Mine was a line by line search to spit out words)
Agree with Kyle. However, in this case, you could do this: egrep "\[#([^]])*)#\]" . -Rohis and get what you're looking for. The [^]]* matches non- ] characters, so it'll You need to do non-greedy match here, to stop at first occurrence. But since grep doesn't support non-greedy match by default, you can use negated character class: echo "word word" | grep -o 'w[^r]*rd' If you've GNU grep, then you can use -P option to enable Perl regex syntax.
For non-greedy match in
grep you could use a negated character class. In other words, try to avoid wildcards.
For example, to fetch all links to jpeg files from the page content, you'd use:
grep -o '"[^" ]\+.jpg"'
To deal with multiple line, pipe the input through
xargs first. For performance, use
You are using .* properly but as you noticed it is greedily eating up as many characters as it can in your match because . matches any character Even if your regular expression engine supports non-greedy matching, it's better to spell out what you actually mean. If this is what you mean, you should probably say this, instead of rely on non-greedy matching to (hopefully, probably) Do What I Mean.
To get a non-greedy match in regular expressions you need to use the modifier ? after the quantifier. For example you can change .* to .*? . By default grep doesn't Vi and Vim Stack Exchange is a question and answer site for people using the vi and Vim families of text editors. It only takes a minute to sign up.
By using non-greedy Perl-style regular expressions, you can prevent this from occurring and stop the search as soon as the search criteria has been satisfied. Teams. Q&A for Work. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information
If you're on an engine that does not support non-greedy match, you can use some trick to achieve that. Note: I will be using GNU grep ( 2.25 ) in a The trick to get non greedy matching in sed is to match all characters excluding the one that terminates the match. I know, a no-brainer, but I wasted precious minutes on it and shell scripts should be, after all, quick and easy. So in case somebody else might need it: Greedy matching % echo "foobar" | sed 's/<.*>//g' bar Non greedy matching
[\D\S] means not digit OR whitespace, both match p> if found, attempt lazy match of any characters until (?s)<p(?(?=\s)\ .*?)>(. if you can NOT find behind.
- eegg: dot all modifier is also known as multiline. It's a modifier that changes the "." match behavior to include newlines (normally it doesn't). There's no such modifier in grep, but there is in pcregrep.
- Correction: In most of the regex flavors that support it, the mode that allows
.to match newlines is called DOTALL or single-line mode; Ruby is the only one that calls it multiline. In the other flavors, multiline is the mode that allows the anchors (
$) to match at line boundaries. Ruby has no equivalent mode because in Ruby they always work that way.
-Pwas a complete new one on me, I've been happily grepping away for years, and only using
-E... so many wasted years! - Note to self: Re-read Man pages as a (even more!) regular thing, you never digest enough switches and options.
- On some platforms (like Mac OS X)
grepdoes not support
-P, but if you use
egrepyou can use the
.*?pattern to achieve the same result.
egrep -o 'start.*?end' text.html
- As an extension to @SaltyNuts comment, Mac OS X does not support
egrephence the suggested
.*?works just fine.
grep -Pdoes not work in GNU grep 2.9 -- just tried it (it doesnt error, just silently doesn't apply the
?. Intertestly neither does the not class eg:
- There's no
grep -Poption or
pgrepcommand in Darwin/OS X 10.8 Mountain Lion, but
- There's a
pgrepcommand on my OS X 10.9 box, but it's a completely different program whose purpose is to "find or signal processes by name".
- @robertotomás Responding to a 6-year old comment here, but....I thought this as well and then realized I was getting multiple non-greedy matches. For instance, on a color terminal you can see that ` echo "bbbbb" | grep -P 'b.*?b'` returns 2 matches.
-shoPnice mnemonic :)
echo "bbbbb" | grep -shoP 'b.*?b'is a little bit of a learning experience. Only thing that worked for me in terms of explicitly lazy as well.