Easy GREP v.1.4 This is an easy-to-use Regular Expression tool for search, extraction and replacement. Tacg - a grep for DNA v.rc tacg - a fast cmd line app in ANSI C for pattern matching and analysis of nucleic acids. The goal of my regular expression is to allow me to break apart IP Table log files so that I can build a basic web front-end to allow me to view the traffic on the network. The MAC address is optional, because the way that this firewall works, is by providing the MAC address when the outbound address is not available. Print $1 Print the part of the regex that was in parenthesis (in this case, the entire regular expression) s/^(foo[^ n]* nbar[^ n]* n)//m Erase the first match for the regex, so we can match multiple cases of the regex in the file in question. The pcregrep tool utilizes all of the same syntax you've already used with grep, but implements the functionality that you need. The parameter -o works just like the grep version if it is bare, but it also accepts a numeric parameter in pcregrep, which indicates which capturing group you want to show.
- Grep Regex Or Operator
- Grep Regex Replace
- Grep Extended Regex
- Grep Regex Log Analyzer Tool For Mac
- Grep Regex Groups
Active1 year, 9 months ago
It seems I am misusing
grep
/egrep
.
I was trying to search for strings in multiple line and could not find a match while I know that what I'm looking for should match. Originally I thought that my regexes were wrong but I eventually read that these tools operate per line (also my regexes were so trivial it could not be the issue).
Grep Regex Or Operator
So which tool would one use to search patterns across multiple lines?
slm♦
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JimJim
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9 Answers
Here's a
sed
one that will give you grep
-like behavior across multiple lines:
How it works
-n
suppresses the default behavior of printing every line/foo/{}
instructs it to matchfoo
and do what comes inside the squigglies to the matching lines. Replacefoo
with the starting part of the pattern.:start
is a branching label to help us keep looping until we find the end to our regex./bar/!{}
will execute what's in the squigglies to the lines that don't matchbar
. Replacebar
with the ending part of the pattern.N
appends the next line to the active buffer (sed
calls this the pattern space)b start
will unconditionally branch to thestart
label we created earlier so as to keep appending the next line as long as the pattern space doesn't containbar
./your_regex/p
prints the pattern space if it matchesyour_regex
. You should replaceyour_regex
by the whole expression you want to match across multiple lines.
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![Log Log](/uploads/1/2/6/1/126127960/678931316.png)
I generally use a tool called
pcregrep
which can be installed in most of the linux flavour using yum
or apt
.
For eg.
Suppose if you have a file named
testfile
with content
You can run the following command:
to do pattern matching across multiple lines.
Moreover, you can do the same with
pradeepchhetri
sed
as well.
Grep Regex Replace
pradeepchhetri
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Here's a simpler approach using Perl:
or (since JosephR took the
sed
route, I'll shamelessly steal his suggestion)
Explanation
$f=join(',<>);
: this reads the entire file and saves it's contents (newlines and all) into the variable $f
. We then attempt to match foonbar.*n
, and print it if it matches (the special variable $&
holds the last match found). The ///m
is needed to make the regular expression match across newlines.
The
-0
sets the input record separator. Setting this to 00
activates 'paragraph mode' where Perl will use consecutive newlines (nn
) as the record separator. In cases where there are no consecutive newlines, the entire file is read (slurped) at once.
Warning:
Do not do this for large files, it will load the entire file into memory and that may be a problem.
Community♦
terdon♦terdon
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One way to do this is with Perl. e.g. here's the contents of a file named
foo
:
Now, here's some Perl which will match against any line that begins with foo followed by any line that begins with bar:
The Perl, broken down:
while(<>){$all .= $_}
This loads the entire standard input in to the variable$all
while($all =~
While the variableall
has the regular expression.../^(foo[^n]*nbar[^n]*n)/m
The regex: foo at the beginning of the line, followed by any number of non-newline chars, followed by a newline, followed immediately by 'bar', and the rest of the line with bar in it./m
at the end of the regex means 'match across multiple lines'print $1
Print the part of the regex that was in parenthesis (in this case, the entire regular expression)s/^(foo[^n]*nbar[^n]*n)//m
Erase the first match for the regex, so we can match multiple cases of the regex in the file in question
And the output:
samiamsamiam
The grep alternative sift supports multiline matching (disclaimer: I am the author).
Suppose
testfile
contains:
sift -m '<description>.*?</description>'
(show the lines containing the description)
Result:
sift -m '<description>(.*?)</description>' --replace 'description='$1' --no-filename
(extract and reformat the description)
Result:
sventsvent
![Analizer Analizer](/uploads/1/2/6/1/126127960/904182271.png)
Simply a normal grep which supports
Perl-regexp
parameter P
will do this job.
(?s)
called DOTALL modifier which makes dot in your regex to match not only the characters but also the line breaks.
Grep Extended Regex
Avinash RajAvinash Raj
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I solved this one for me using grep and -A option with another grep.
The -A 1 option prints 1 line after the found line. Of course it depends on your file and word combination. But for me it was the fastest and reliable solution.
mansurmansur
Supppose we have the file test.txt containing :
The following code can be used :
For the following output :
Nicolas Pollin-BrotelNicolas Pollin-Brotel
If we want to get the text between the 2 patterns excluding themselves.
Supppose we have the file test.txt containing :
The following code can be used :
For the following output :
Grep Regex Log Analyzer Tool For Mac
How does it work, let's make it step by step
/foo/{
is triggered when line contains 'foo'n
replace the pattern space with next line, i.e. the word 'here'b gotoloop
branch to the label 'gotoloop':gotoloop
defines the label 'gotoloop'/bar/!{
if the pattern doesn't contain 'bar'h
replace the hold space with pattern, so 'here' is saved in the hold spaceb loop
branch to the label 'loop':loop
defines the label 'loop'N
appends the pattern to the hold space.
Now hold space contains :
'here'
'is the':gotoloop
We are now at step 4, and loop until a line contains 'bar'/bar/
loop is finished, 'bar' has been found, it's the pattern spaceg
pattern space is replaced with hold space that contains all the lines between 'foo' and 'bar' that have saved during the main loopp
copy pattern space to standard output
Done !
Nicolas Pollin-BrotelNicolas Pollin-Brotel