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

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How to search and replace multiple needles by one word via one expression?

Assume you have a text file: foo fnord bar bizz foo poit And now I would want to replace both "foo" and "bar" into "narf". I know I could use: sed -e 's/foo/narf/g' -e 's/bar/narf/g' fileName ...
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Search and replace strings that are not substrings of other strings

I have a list of replacements like so: search_and -> replace big_boy -> bb little_boy -> lb good_dog -> gd ... I need to make replacements for the above, but at the same time avoid ...
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Using a perl compatible regex with GNU grep -P

I'm using this regex (?<=\[')[^,]* on a file containing the following line disk = ['OVS/sdasd/asdasd/asdasd/something.img, w'] I want that to return OVS/sdasd/asdasd/asdasd/something.img How do I ...
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Using regular expressions with cp

This is a simple question. I'm trying to copy all of the files in the current directory that start with "axis-2" and end with ".jar" into a target directory, let's say it's ~/MyDirectory. My first ...
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How to select first occurrence between two patterns including them

How can I select first occurrence between two patterns including them. Preferably using sed or awk. I have: text something P1 something content1 content2 something P2 something text something P1 ...
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Finding the number of time a particular number in a file where range also specified

I have a file with numbers separated by ,(comma). In between it also contains a number range like 300-400. Say for example I have a text file, namely testme.txt which looks like, ...
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How can I extract the numbers in the file using sed or any other tool?

I have a file that has this format [ 2014/05/01 10:48:26 | 13963 | DEBUG ] It took 11.16837501525879 seconds to complete the process So I have thousands of lines like this and I would like ...
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Sed: replacing digits

I am trying to write some install scripts for when I install/upgrade Ubuntu. I'm having trouble with fixing logrotate.d: /var/log/ufw.log { rotate 7 weekly missingok notifempty compress delaycompress ...
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What is the python equivalent of grep -v?

I like grep -v. I use it all the time. But I am also doing some text processing in python, and there is one crucial thing that I lack. Usually, I use grep -v to take extraneous stuff out of text. ...
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grep caret appears to have no effect

I was under the impression that a caret symbol means "beginning of the line" with Extended POSIX regular expressions. However, when I use it with grep it behaves unexpectedly. #grep --version GNU ...
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command: ls /etc | sort | grep d* is yielding no results but ls /etc | sort | grep p* lists entire directory

I am playing around with piping and grep tonight. I know that grep uses regex and that * means 0 or more occurrences of the preceding character. So the way I understand it is that if I do the ...
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How to grep for pipe |

How can I grep for line containing pipe character | or for character >: files content: |this is test where is > this is none now what I need using grep command is grep -iE "<some ...
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Sort input file by the results of a regex

I'd like to sort a file based on the results of a regex expression. For example, if I have the following property declarations in Obj-C @property (nonatomic, strong) id <AlbumArtDelegate, ...
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Match regex in ksh

I am looking to do something like this in KSH: if (( $var = (foo|bar)[0-9]*$ )); then print "variable matched regex" fi Is it possible at all? For the record I'm using Ksh Version M-11/16/88i ...
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In a regular expression, which characters need escaping?

In general, which characters in a regular expression need escaping? For example, the following is not syntactically correct: echo '[]' | grep '[]' grep: Unmatched [ or [^ This, however, is ...
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Use sed to delete all but a certain pattern

How do I get just the link part in the http-source of a link? I have <a href="http://unix.stackexchange.com/users/20661/">Unix &amp; Linux and would like to get just ...
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how to use regex in alias?

I want to create the alias for the command "ssh user@10.32.44.225" as 10.32.44.225 alias [0-9][0-9][0-9].[0-9][0-9][0-9].[0-9][0-9][0-9].[0-9][0-9][0-9]="ssh user@$0" I have created it, but it is ...
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Insert Lines after Multi-Line Regex Match

I've got an XML file I need to append to after a specific set of tags. Basically the file structure looks like this: <key>servers</key> <dict> ... Server Details ... </dict> ...
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Why does grep treat '[D]ebug' string differently?

I've created simple text file named "T" to test the unusual behavior of grep: 1 Debug 2 debug 3 determined 4 Determined Tried different syntax: $ grep De T 1 Debug ...
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Why sed prints first string from file even if it's failed to find matching groups

I'm trying to write sed expression which will extract matching groups from file. E.g. I have .cue sheet and I want to extract it's genre tag. It has following format: $ cat file.cue | grep GENRE REM ...
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Remove string from a particular field using awk/sed

I have a file (>80,000 lines) that looks likes this: chr1 GTF2GFF chromosome 1 249213345 . . . ID=chr1;Name=chr1 chr1 GTF2GFF gene 11874 14408 . + . ...
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with sed, how can I replace word within a matching line?

I am trying to write a sed expression to detect lines similer to this: s0:12345:respawn:/sbin/agetty -8 -s 115200 ttyS0 linux and replace the "ttys0" with "something_else" I do not want to detect ...
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match files based on an md5 using find

I have a bunch js and css files in a directory. Some of them have been given a name based on an md5() of their content (looks like f10521a21bb013cb81e0909809818ad6.js). I'd like to match these files ...
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VIM substitute occurrences of pattern after a particular word in a line

I have such lines in my text. text before pattern = garbage** text after pattern is pattern If in VIM I do %s/pattern/saturn/ it replaces all occurrences of pattern. But I only want to replace ...
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escaping a single dot with double backslash - awk

"effective awk programming" book has an example on Field-Splitting. here is the example: If you want fields to be separated by a literal period followed by any single character, use ‘FS = ...
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Replace a substring of filenames in a directory

There exists a directory, which includes several levels of sub-directories. Under these directories, there are a set of files whose names include a common word, e.g, .cc. How can I replace the .cc ...
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substrings and regexps

I have a string contained in a variable, and I want to extract substrings based on position relative to another substring. My solution seems to work unless the string is sent to a function as an arg. ...
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320 views

Trouble with grep -o regex

I'm trying to use a grep command with the --only-matching flag, but it's not behaving as I would expect it to. This command: echo "1/2/3/4/5" | grep -oE "^([^/]+/){0,2}" Gives this output: 1/2/ ...
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Find files in multiple folder names

I am trying to list all the files from dir1, dir2, dir3 and dir4 which might be anywhere in as a sub directory of my cwd using the find command. I tried the following with no success: find . -type f ...
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substituting third occurrence of a pattern using sed

Here is a sed command. I want to substitute third occurrence of 00 to 11 echo "0000000000000000" | sed -e 's/00/11/3' The output is: 0000110000000000 But I thought output would be: ...
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Substituting the first occurrence of a pattern in a line, for all the lines in a file with sed

Is it possible to do it in one liner? I have an output like this: "First line" - Description " Second line" - Description "Third line" - Description " Fourth line" - Description This input ...
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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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How to find files with names having a long string after the first dot

My Samsung Galaxy S doesn't like files where the name contains a long string after the first dot. I guess some part of the software has a too short buffer for the file extension. How can I find all ...
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Print repeating pattern

I have a marathon file from which I want to print the names of the runners, who have made multiple runs. Something like: M, 2:08:58.0, John Lukas, USA, 1997-07-25, Paris, France F, 2:15:04:0, Abebbe ...
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regexp which matches all tokens independent of order

I have a quick (and hopefully simple) question about regexps. I'm trying to think of a regexp which matches all of a set of tokens irrespective of order. So for example I have a file with the names ...
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greedy and lazy regular expressions (comprehension question)

I am teaching myself regular expressions, and I got stuck at »greedy« vs. »lazy« repeatings. What I found out so far is that »greedy« means that the RegExp ...
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find command with regex {1,2}

I have been trying to create a find command string that will find all files that end with a number 1-99 but exclude all others. e.g. I want to find myfile1 myfile99 but not myfile456 and not ...
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How can I find and replace only if a match forms a whole word?

My script is: n="y" while [ "{n}" = "y" ] if [ $n == "n" ]; then break; fi echo "n is $n" do read -p "Enter the word to find = " word read -p "Enter word to replace = " replace ...
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Regex this question format into LaTeX

1. Lorem ipsun la la la? 1. Sopor 2. Stupor 3. Torpor 2. A patient has Lorem? 1. Sopor 2. Stupor 3. Somnolentia 4. La 5. Coma 3. Doesn't Response to strong external irritants is short. Tendon, ...
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Match word containing characters beyond a-zA-Z

To match a word one can use \v(\w+) From the vim help :h \w: \w word character: [0-9A-Za-z_] This works exactly as described in the manual. However, I want to match words that contain ...
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File manager which is able to filter using regular expressions

Is there any graphical file-manager which supports thumbnails for linux like thunar or nautilus, which allows me to filter a directory by a regular expression. For example typing /home/user/*tex ...
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Replace using vim - Replace a pattern […] by a string

I have a file containing lines in below e.g. format - [foo@host.com, bar@host.com], Payment processed - 23499, params = {'invoice':3243} I only want the account numbers i.e. 23499. It's a number. ...
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sed regex issue

I'm trying to replace a string in a file: $RELEASE = '1234'; The whitespace between RELEASE and the = symbol could be either spaces OR tabs. The quotes around the version number could be either ...
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Using Regex in vim movment

Is there any way to use regular expression for movement in vim. For example, I want to move my cursor to the first occurrence of the pattern abc. So can I do something analogous to fa but now a ...
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Is there a tool in linux that allows multi-line regex expressions?

I'm wanting to find the results of a multi-line regular expression in linux. I tried grep, but like most linux utilities it's line based. Is there something similar that allows me to search across ...
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Are there zero-width assertions in sed?

Is it possible to make lookahead or lookbehind zero-width assertions in sed? I want to emulate Perl's (?=) and family. My sed is not GNU sed version 4.0.
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Parsing XML from a shell script

I have a datafile like this: <Key name="com.ahsay.afc.cpf.UserGroup" content="" allowMultiple="Y"> <Value name="rsv-id" inheritParentAttribute="Y" type="string" data="1328200856753" ...
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How to grep the n-th substring between given delimiters?

Let's say we have a string and its delimiter is ?: Leslie Cheung April 1 ? Elvis August 16 ? Leonard Nimoy February 27 I know how to grep the first substring between delimiters: echo $above_string ...
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Decreasing a number with sed

I extracted the metadata of a PDF in a .txt file using pdftk, and now I am trying to decrease the BookmarkPageNumber value for each bookmark by an integer. The .txt has these lines: BookmarkBegin ...
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Multiline regex blank line delimiters,

I have a program which prints out data in blocks. Each block is delimited by blank lines. I would like to discard most blocks and only keep those blocks that contain something that matches a regex. ...