Regular expressions are a means of matching a pattern of characters within a string.

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Delete XML node containing certain element

I want to remove all Placemarks from a KML file that contain the element <tessellate>. The following block should be wholly removed: <Placemark> ...
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How to “grep” a string of a returned result

How to grep the number 50.0 from the string temp=50.0'C In JavaScript I can use the expression /temp=(.*?)'C/ to get it. But I cant get it running in grep.
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How to use restricted characters in egrep?

I'm trying to use a regex in egrep on Centos 5.10, based on the one I made from this question on SO. T12345 .{1,100}[\n\r].{1,100}2014.03.04 I can successfully match the regex to the content in my ...
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“grep: Unmatched [” error when using regex

I'm trying to find a pattern similar to this: tail -n 100000 gateway.log | grep -B10 -A10 'Nov 22 11:13:56 Received Packet from [10.50.98.68' Where "11:13:56" could be any time. This is what I ...
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changing pattern of a text file

A text file has contents something like chair table pen desk Now i want it to be changed and stored in a variable say var as below ('chair','chair'),('table','table'),('pen','pen'),('desk','desk') ...
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Awk: check for length of field

In awk. I am working on Solaris 10, so it's probably an old(er) version of awk. I came up with this rudimentary one-liner that works, at least for my particular input. awk -F\; '$3 ~ /[ ...
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Using regex inside if clause in bash

Look at this if block: #!/bin/bash str="m.m" if [[ "${str}" =~ "m\.m" ]]; then echo "matched" else echo "not matched" exit 1 fi exit 0 This should print "matched", but it doesn't. ...
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Applying a regex to stdin

In programing we often see the use of Regular Expressions. One of the most common forms is: newText = text.replace( /regex/, 'replacementString' ) If stdin is text and stdout is newText, what ...
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Why awk understand FS=“*” but not for FS=“-*-”?

I got a test file, its content is: a -*- b I used awk 'BEGIN {FS="*"} {print $2}' test, it prints out - b Correct! But when I use awk 'BEGIN {FS="-*-"} {print $2}' test, I got: * I know that ...
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Regex match in CLI

Is there something like a logical for the cli? I want to achieve this mv -t newfolder *.(png|jpg) so that alls jpg and png files are moved into newfolder. I know it could be done with mv -t ...
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Extracting text from a text file in bash

I have a large text file that is all one line. In the text are several sections that looks like foo=12345 and I need to extract them all as separate lines, ignoring the rest of the file. For ...
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pattern match and capturing in unix

I have a file like this: A1-1915435_1_MIMAT0000069_MirBase_miR-16_microRNA_1_22-A1-1915435_1_ENSG00000206737_ENST00000384010_U1_snRNA_73_115 ...
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Using a variable in a regex

How can I use a variable string in a regular expressions while read line do if [[ line =~ *"$key"* ]]; then echo line fi done < "$filename" $key is a string ...
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sed - how to (not) match unmatched brackets

How can I do my operation only on lines that close their brackets? For example I want to change ".is" lines and add a bracket but not for lines with unclosed brackets. so these are changed ...
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Replace all occurences of \ except \N

I have a file like this: 1,2,subjects,\mat\hs,unix\,\Nato,\N,123,\N I want to replace all occurences of \ with #, except for \N, such that the output looks like this: ...
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Do procmail recipes have an alternator “or” operator?

Given the following procmail recipe: :0: * ^Subject:.*viagra.* * ^From:.*viagra.* /dev/null Procmail would only delete emails that were both from viagra, and had viagra in the subject. Is it ...
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What is the usage of pattern before substitute command in sed

There is an example in this link about sed: To delete the first number on all lines that start with a "#" use: sed '/^#/ s/[0-9][0-9]*//' What is the benefit of first pattern(/^#/)? It could be ...
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Find files starting with ~$ (MicroSoft Word Temp files)

For some reason my machine is full of M$ Word temporary files such as: ~$Filename.docx ~$AnotherFile.docx Can someone suggest a find/regex command to search $HOME and delete them?
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splitting textfiles according to a regular expression

By pasting into a text editor, I have a textfile gleaned from an online edition of Wilhelm's Yi Jing translation which I now want to split into 64 unequal parts, according to the 64 hexagrams of the ...
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Extract specific set lines matching a rule

I have a large file with the logs as shown below. There are about 30000 instance of such events logged. I need to extract those lines beginning with RINGING and CLOSE (included) and which does NOT ...
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simple command to strip header and footer from a file

I want a simple little command to strip an XML-Header and Footer from a file: <?xml version="1.0" encoding="UTF-8"?> <conxml> <MsgPain001> ...
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ANDed conditional using regexp and variables

I want to test whether a line, read in from a file, has a specific beginning AND an ending containing a word held in a variable. Here's some code: The input file is: line one #; line two #; line ...
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sed or tr one-liner to delete all numeric digits

So, I have this textfile, and it consists of mostly alphanumeric characters. It's a standard document. But since I copied it and pasted it from a PDF, there are page numbers in there. I don't much ...
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Capture in shell variables the arguments after a command (between brackets)

Suppose I have a file that contains, among many other things, \command{arg1,arg2,arg3} (arguments been paths, expressed with /, ., characters and numbers) But that a user can as well call it ...
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Strip off word pattern at the end of string using sed

I have following string: ksh -x SCRIPT2.ksh $BUSSINESSDATE & PID=$!; ksh -x SCRIPT1.ksh $BUSSINESSDATE & PID=$!; I want to strip off the last word & PID=$!;. Desired result is: ksh -x ...
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Sed: modify every non-first word repetition for every word in text

Can you help me to do something like that using sed? qq ab xyz ab qq aa ab Becomes: qq ab xyz +ab+ +qq+ aa +ab+
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Replacing a pattern in line preceding another pattern of interest

I have a log file with many instances of statements as shown below: 14 Aug 19 16:30:11.506: <DATA> |POS|IDLE|1|01131844090|5950|$hostIp|$size |$data 20 Aug 19 16:30:12.439: <DATA> ...
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Replacing string in all files found by grep. Can't get it to work

I'm trying to do what title says. So I find all needed files with grep: grep --include=\*.{php,ini,conf,sh} -ril -P "'([\d\w\-\_\.]+)(@domain.com)'" '/var/www_data/somepath/' Now I assume it's ...
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Why doesn't this regex work?

I want to look at the output of git status -s to determine whether there are any untracked files in the tree. I tried the following test, but the regex doesn't match. Why not? $ git status -s ## ...
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find utility does not recognize bracket notation

I've two files in the current folder: submitWeb.m submit.m the following find does not show the two files: find . -regex .*submit\(Web\)?\.m But the above regex expression works fine in ...
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How to add a line in many files

I have many .html files and I need to add a meta tag after <head>'s start tag in each file. How I can do that? Can vim help me?
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Why isn't this sed regex matching?

I've recently started learning sed. I did $seq 10 | sed '/[^049]/d' I was expecting 4 9 10 as output. But I got 4 9 Where am I making mistake in understanding this regex?
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Why does my grep expression need to use $'string' to match tab characters?

If you take this code: echo -e '\t\t\tString' | grep '^[\t]*String' the result is blank because it doesn't match, yet this: echo -e '\t\t\tString' | grep $'^[\t]*String' works. I swear that I ...
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Extracting just a single group from a regular expression

I am trying to get a list of numbers from some hacked-together log files using zgrep. So, I am using: zgrep -ie "total time: .* ms" * This returns the whole line that I care about. I'd just like ...
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Get all regex matches between two patterns and print them to file

I've got a file with a bunch of long lines. I'd like to grab every group between two patterns and print them to a new file, one match per line. I could manage to do this with Python, but I'd prefer ...
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Escaping of meta characters in basic/extended posix regex strings in grep

Is it possible to escape all meta characters of a string inside a variable before passing it to grep? I know similar question has been asked before on SE (here) and also a good explanation here, but I ...
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grep and escaping a dollar sign

I want to know which files have the string $Id$. grep \$Id\$ my_dir/mylist_of_files returns 0 occurrences. I discovered that I have to use grep \$Id$ my_dir/mylist_of_files Then I see that the ...
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What does . match?

In working with regular expressions, I have been told that a dot character . will match everything. Except for newlines \n. Are there any other exceptions? What about the NUL character \0, or the ...
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Grep - ^(\s*$) vs ^\s*$

I want to search for a field that only has spaces. When counting, this two commands gave me different results: grep "^\s*$" -E -c grep "^(\s*$)" -E -c Another thing. What is the correct way to say ...
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Using sed to replace only the first two regex catches with different strings

So I'm trying to change two instances of a regex pattern to two different strings with sed like: sed -E "s/\\t([A-Za-z]|[-])+$/\\t`get_addr.py -1`/" /path/to/file.ext sed -E ...
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Problem with regular expression in gawk ('\<' not working)

I am trying to get into bash a little bit. I was going through this guide but the second example in this subsection on gawk doesn't seem to work. The problem is this command: ls -l | awk ...
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Accept only y or yes with a one-line regular expression

I want to check if an input is y or yes (inputs in lowercase) and reject everything else What I have now is ^y[e]{'0,1'}[s]['0,1']$ But this accepts y, ye, ys, yes. I don't want ye and ys to be ...
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How to perform a multiline grep across multiple files?

I'm trying to grab this pattern wherever it occurs in multiple log files (Note:these patterns can vary greatly in size, i.e. the amount of Blahs): Found an txt File Blah Blah 10019874 ...
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pcregrep newline lookbehind assertion bug?

Attempting to use pcregrep to print the first line after a blank line. For example, contents of file first line second line I need second line to be printed. Here are a few tests using the same ...
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Merging text files based on their filename

I have hundred of files with the following format: 2013_01_19_xyxyxyx.txt 2013_01_19_xyxyxyx.txt 2014_03_21_xyxyxyx.txt 2014_03_21_zxzxzxz.txt 2014_03_22_abababa.txt 2014_03_22_cbcbcbc.txt etc. I ...
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Replacing 3 or more digits with equivalent number of *

I want to replace any 3 or more digit string in a text file with equivalent number of *.For example: abc-1234-45 --> abc-****-45 echo "abc-1234-45" | sed 's/[0-9]\{3,\}/*/' I tried this but it only ...
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Expanding comma-separated list into separate lines

I have a file with some data in this form: Prefix text: First Name, Second Name, Third-- The prefix differs by line. The number of names varies from one to several. The suffix (-- in the example) ...
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How to insert both vimscript variable and string into vim search and replace

I've only just found out about Vimscript's existence as of today, so forgive me if this question is more basic than it seems, but I've been struggling to find an answer to this question for the better ...
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Bash regex matching not working in 4.1

Upgraded to Bash4 and found that it is not matching regexes: $ echo $BASH_VERSION 4.1.2(1)-release $ [[ "20110228" =~ "^[0-9]{8}$" ]] && echo matches But Bash 3.0 is: $ echo $BASH_VERSION ...
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Using grep/sed/awk to classify log file entries

I need to process a very large log file with many lines in different formats. My goal is to extract unique line entries who have the same starting pattern, e.g. '^2011-02-21.*MyKeyword.*Error', ...