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

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sed one-liner to delete any line that begins with a digit

Pretend I am working with this file. The beginning of the first visible line is obscured, so ignore that. 43 is the beginning of the next line, and that line would be deleted. The next line (which ...
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773 views

sed, grep, or tr command that returns only Latin characters from a UTF-8 file

I am working with the text of the 300 tang poems, which unfortunately is a single file containing both Chinese and English. Since I am interested in 'extracting' the English, I hope to use sed, ...
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Can tr work with regex?

I have a file like this: AAAA BBBB CCCC DDDD etc Words in separate lines. I want to add them quotes using tr. So I tried the following: 1) To add a quote in the start of each word ...
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How to find files with a certain subpath?

I need to find all xml-files that are placed in folders named config. Also config must be somewhere under a folder named trunk. For example, I am interested in all files like below: ...
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217 views

How can I remove lines matching foo but not matching bar?

Assume I want to remove the 2nd and 3rd, but not the 4th line in the following file (those which match foo but do not match bar), can I easily do this with e.g. sed? text foo some more text even more ...
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Apply item replacement inside enumerate in Perl regex?

Data 7. Masi is the same as \begin{enumerate} A B ABC ha lorem \end{enumerate} 1. ABC is \begin{enumerate} P B Lorem maam \end{enumerate} which I want to be 7. Masi is the same as ...
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Extract IP address from a string

The Linux host command returns: hostA.domain.com has address xx.xxx.xxx.xx How do I get just the IP address and put it in the $ipaddr variable? open(FILE, "hostlist.txt") or die("Unable to open ...
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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 change only start of line and preserve end of line

Basically I have a situation where I frequently need to modify my hosts file to access different servers at my workplace. In an attempt to automate the process. I've been trying to use sed to make the ...
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Pulling out keywords using standard command line utilities?

As an example, this is the pronunciation of "when" according to Wiktionary. enPR, IPA and X-SAMPA are different schemes for showing pronunciations. when:* {{a|US}} {{enPR|wĕn|hwĕn}}, ...
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Find word in sentence with Bourne Shell (sh)

I'm trying to determine if a particular word appears in a sentence using Bourne Shell (sh). For example: #!/bin/bash INPUT='Lorem ipsum dolor sit amet.' if [[ "$INPUT" == *dolor* ]] then echo ...
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Remove backslashes from a text file

I have Input: NISHA =\455 Output: NISHA = 455 I want to remove \ from output. I tried to use command sed "s/[\]//g" P but it is not working and it flags an error: character found ...
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395 views

Regex doesn't work with grep

I have a string like this TEST="/dev/sda1 on /media/sda1 type vfat (rw,relatime,fmask=0000,dmask=0000,allow_utime=0022,codepage=cp437,iocharset=iso8859-1,quiet)" (Result from mount | grep sda1) ...
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Why don't I need to escape a character class in sed but I need to escape the rest?

I am confused with sed. I had a file with the following contents: [ 2014/02/10 14:45:15 | INFO ] Saving data for customer: 273667 [ 2014/02/10 14:45:15 | INFO ] Saving data for customer: ...
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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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Understanding -regex with GNU find

Background I have what I think should be a simple case. I want to find all files with "cisco" in the name and do something with those files (via xargs). Finding files with ls Before I use xargs, ...
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awk, sed, grep, perl… which to print out in this case?

I have this syntax in a file (http response times from analog): <thead><tr><th class="x">seconds</th><th class="R">reqs</th><th ...
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356 views

changing pattern by removing spaces?

file : hi hello,new york, , ,brazil site ,brazil january,month is feb , , ,indiana jones task: delete all horizontal space (spaces and tab) between any two comas (like , ,) if ...
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405 views

Detect pattern repetition in a file

I want to make sure a file follows the following pattern: ... ... ... foo ... foo_KO ... ... ... bar ... ... ... ... bar_KO ... The file is extremely long, so, in other words, I want to make sure ...
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240 views

bash - extract filenames from html file containing multiple links

I have downloaded an html file autogenerated by a script on a webpage. The file contains multiple links, including links to images I am trying to extract the full names of the images, for example ...
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161 views

sed regexp HEX char

i have this string: echo -e "a12\x8fb12\x9f"|xxd 0000000: 6131 328f 6231 329f 0a a12.b12.. i want delete this sequence string 12\x9f and 12\x8f with sed. i can do it with this ...
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Find a pattern with no repeated numbers in egrep

I need help finding a regular expression to match all digit sequences which has no repeated digit. Example: 198345 -> matched. 198315 -> not matched (1 repeated twice ) How can I achieve this in ...
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extract last match from logfile till end

Using sed, grep, awk, or ruby, what's a simple way to find the last match of a string in a larger log file, and send every line following it (inclusive) to another file? Example: grep -A222 ...
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remove white space before delimiter with sed

I have data of the following format that I want to input into LibreOffice calc data | num | num | num | num For some reason Libreoffice does not think the string "3214 " is a number by ...
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193 views

sed one-liner to delete word-medial spaces

I have a text file that consists of some N ORMAL E NGLISH W ORDS in all-caps. Unfortunately, these words all have a space between the first and following letters, which is not acceptable. I tried ...
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Filtering paths to a specific depth

I'm using rsync and the flags -nPaAXz ~/ to check which files are going to be copied. This is far too verbose to make any sense of. How could I filter the output so I view the list of files/folders ...
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regex - Searching for only character pairs

I have the following data from which I mean to extract only those lines which contain "bb" only. Not "b" or "bbb" or anything else just "bb". abb abbb aabbcc aabab abbbbc Now when I use the ...
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510 views

grep to find words with all vowels

Using grep -E and regular expressions I need to find words containing all of a group of characters in no particular order. For instance a word containing all vowels (aeiou) however the vowels can ...
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Yum regular expression or wildcard search?

Fedora documentation says: 5.2. Advanced Searches If you do not know the name of the package, use the search or provides options. Alternatively, use wild cards or regular expressions with ...
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can regex capture groups be used in GNU find command?

With the GNU find command (GNU findutils 4.4.2), a regular expression can be used to search for files. For example: $ find pool -regextype posix-extended -regex ...
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Condition string matches reg.expression

So, in my script, I have to decide whether one of the parameters is a valid email address. I was trying, but it failed. if $maddr="^.$*\(@\)\(*\)\(.\)\(??*\)" then ... It's meant to mean: at least ...
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How to print strings matching a pattern with grep?

I want to get a list of strings matching the following pattern: CLASS_NAME:"*" where * represents any number of characters. I tried: grep -o CLASS_NAME:\".*\" script.js and grep -o ...
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225 views

Counting consecutive repetitions of a specific character (e.g. ,)

Say I have a file with lines like the two following: foo,bar,,baz,xy foo,,bar,baz,xy,, I would like to count how many times I have ,, (two consecutive commas surrounded by any other character) in ...
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Trouble getting regex to work with find

I'm having a lot of trouble getting find to work with regex flags. Im using egrep on its own to find a date pattern in a file, like this: egrep '[0-9]{4}-[0-9]{2}-[0-9]{2}' which will return dates ...
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How to Replace Path in Search field using VIM

I'm trying to replace this text in VIM Actual Path /home/omipenguin/Servers\ Information/systemscript.sh/sysinfo.txt with this new path /home/sysinfo I tried %s/\/home\/omipenguin\/Servers\ ...
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regular expressions with grep

I have this command right here: grep -B10 -A10 '14:14:50 {"channels":["/alerts/6979/new"],"data":"New alerts for unit 6979"}' mygateway.log Rather than searching for 14:14:50 I would like the 50 to ...
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202 views

grep all words with specified length, without letter x

So I am stuck here: grep -E '^....c...c...$' shows all words with the expr I need. Now from this words I only need the ones that don't have a x. Who can help me?
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AWK match string, not Regex

How do I match a string with AWK? Say I have the string [(*.+ it should only match strings containing the string [(*.+. The string is entered by the user, so if you know a cli utility that can ...
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How can I find all files in a folder that contain a match of a regular expression in the file name?

I'd like to find all of the files in my home folder on Linux (Ubuntu, in this case) that contain a match a particular regular expression. Is there a simple Unix command that I can use in order to do ...
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Stripping all vowels but the first from a set of strings

I have a string comprised of multiple substrings, separated by underscores. For example: AbcdAEfd_hEgdgE_AbAAAAA. I need to remove all vowels except the first from each substring. So: AbcdAEfd -> ...
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How to do a regex search in a UTF-16LE file while in a UTF-8 locale?

EDIT: Due to a comment Warren Young made, it made me realize that I was not clear on one quite relevant point. My search string is already in UTF-16LE order (not in Unicode Codepoint order, which is ...
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1answer
262 views

Delete repeated words between brackets inline

Our input looks something like 2012-04-17 [GBPGBP] 2012-04-13 [GBP GBP] 2012-04-13 [GBP] 2012-04-11 [GBPGBP] 2012-04-11 [GBP GBP] 2012-04-10 [GBPGBP] 2012-04-06 [GBP GBP GBP] 2012-04-17 ...
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Find all lines in a file with a certain character at a certain position

I have a lab question asking me to use grep with a regex pattern to match every word where the third letter from the beginning of the line is an "a" and save it with a redirect. How can I do that?
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expr help - managing strings

I need to take text like this: A234321=http://www.google..... a normal URL And pull out only the URL, getting rid of the first part. I think I can use expr to do it, but I can't figure out the ...
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Regex : match 2nd and 3rd character

I was doing some exercises on regular expressions, but I can't seem to be able to crack this one : egrep in a file where the 2nd and 3rd character are the same. I tried : egrep '^..{2}' ...
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Checking if an input number is an integer

I'm trying to check if an input is an integer and I've gone over it a hundred times but don't see the error in this. Alas it does not work, it triggers the if statement for all inputs ...
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Awk regular expression syntax with number of repetition - different handling between gawk 3 and gawk 4

I am having trouble understanding or explaining why the following expression fails in gawk 3.1.x and yet works in gawk 4.1.x: (Minimum working example) echo ";#ADCDE#" | awk '/#.{5}#$/' -> produces ...
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Search for “not newline” in vim?

To search for A T\n in vim I can just do /A T\n What would be the equivalent for not newline at the end? /A T[^\n] did not work.
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Print some fields of /etc/passwd

I have a question concerning the usage of wild cards in Linux. Here I have some lines from a long list of lines in the /etc/passwd -file. root:x:0:0:root:/root:/bin/bash ...
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mv files to a different path which is constructed via a regex replacement

I have a directory full of files stored in subdirectories according to their filename, i.e.: 20d1/d325/52d1/20d1d32552d1a95249e62662fbdf924dd72c4027.jpg ...