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

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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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104 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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3answers
182 views

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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2answers
270 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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2answers
1k views

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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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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1answer
192 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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3answers
741 views

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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3answers
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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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3answers
95 views

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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2answers
52 views

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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2answers
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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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1answer
246 views

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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1answer
205 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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2answers
154 views

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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2answers
140 views

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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1answer
189 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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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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2answers
410 views

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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4answers
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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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4answers
601 views

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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1answer
256 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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2answers
7k views

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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3answers
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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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105 views

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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1answer
285 views

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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1answer
121 views

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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355 views

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 ...
2
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3answers
171 views

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 ...
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1answer
2k views

Forcing Bash to use Perl RegEx Engine

As you may already know, a lot of the features modern RegEx engines support (back referencing, lookaround assertions, etc.) are not supported by Bash RegEx engine. Following is a simple Bash script I ...
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How to reverse-match a string in the Vim programming language?

I want to find the last index of any character in the [abc] set in the abcabc string but the search should start from the end of the string: " Returns the 0th index but I want the 5th. let ...
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1answer
4k views

sed special character replace not working in shell script

I want to write a script 'test.sh' that will take a user's input and replace all special characters with a '\' + the character. My script: #!/bin/bash echo 'input='"$1" arg=`echo "$1" | sed ...
2
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1answer
189 views

prepend digit to filenames which begin with digits (with zmv, please)

I have a directory with files named like 19.png, 20.jpeg, and README00.txt I want to rename these to 119.png, 120.jpeg, and README00.txt. I would like to do this with zmv as it works well in so many ...
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1answer
325 views

How to join vCards lines

vCard uses a special way to split long lines: At 75 characters, insert a DOS newline and a space. Joining therefore means to replace all occurrences of the sequence "CR, LF, space" with an empty ...
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Sort by regular expressions

I've got a set of POSIX regular expressions* ^BEGIN:VCARD\r$ ^VERSION[^A-Z] ^FN[^A-Z] ^N[^A-Z] ^NICKNAME[^A-Z] ^EMAIL[^A-Z] ^X-\([A-Z-]*\) ^TEL[^A-Z] ^ADR[^A-Z] ^ORG[^A-Z] ^TITLE[^A-Z] ^BDAY[^A-Z] ...
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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 ...
2
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1answer
602 views

Emacs: query-replace, regular expression, reuse of search result

How do I combine something like query-replace with a regular expression search-and-replace that in part reuses the search result? In my case, how to transform The programmers are "sort of" ...
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2answers
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How do I transfer multiple files with a common suffix and prefix using an offset?

I have thousands of files whose names are of the form: sequence_1_0001.hmf sequence_1_0002.hmf sequence_1_0003.hmf ... sequence_1_0001.jpg sequence_1_0002.jpg sequence_1_0003.jpg ... ...
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128 views

Does find support OR in its regexes?

For example, I want to find all files in a directory that end in 'm' or 'sh'. The following works correctly: find . -regex '.*.m' -o -regex '.*.sh' But this fails: find . -regex '.*.(m|sh)' What ...
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2answers
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How to treat a file as a single line with grep to apply a regexp search pattern?

I want to match everything that is between some lines with regexp but not this that match the start and the end. This sound to me as positive lookbehind and positive lookahead start text bla ...
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1answer
555 views

Regex : how to verify that there are 13 greek letters with an odd number of consonants

Another regex that I can't seem to crack :( I tried with egrep '([qwrtzpsdfghjklxcvbnmy]{1})|([qwrtzpsdfghjklxcvbnmy]{3})|([qwrtzpsdfghjklxcvbnmy]{5})|([qwrtzpsdfghjklxcvbnmy]{7})' greek.txt ...
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Arithmetic operations in regex

I am using gedit regex plugin (Python style regex). I would like to do some arithmetic operation on a backreference to a group. For example: PART 1 DATA MODELS Chapter 2 Entity-Relationship Model ...
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4answers
71 views

replace several comma out side one or more sets of curly braces and exception that in one or more sets of curly braces

In the text file I have multi records. Every record has multi column with comma separated, some column have one sets of curly brace and other have more than one curly brace. I need: If a comma is ...
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2answers
43 views

What is the regex to validate Linux users?

When adding a new user, how is the string validated? I suppose there is a regular expression. What is that regular expression?
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2answers
79 views

Find characters in the file

I need to find lines in the text file that have at least one x and at least two ys. I tried the following: grep -E "x.*y{2}" file.txt This method did not work. Is there another way to do it?
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4answers
180 views

Matching string with a fixed number of characters using grep

I am trying to find all 6 letter words using grep. I currently have this: grep "^.\{6\}$" myfile.txt However, I am finding that I am also getting results such as: étuis, étude. I suspect it has ...
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1answer
245 views

Removing non-printable characters using POSIX sed

Files created with roff and other "old-school" tools (for example man pages on many Unix systems) generate bold and underlined text in minimalistic terminals using tricks involving non-printable ASCII ...
2
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1answer
53 views

Context of the matching regular expression

I'm using egrep with the -o option in order to just get the matching part of the line, e.g. cat /usr/share/dict/words | egrep -o '(aa|ii)' Now I'd like to see some context of the match, i.e. a few ...
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A challenge for sed convert code from Mathematica to Matlab

I have the following output from Mathematica to C code: $ cat file.txt Complex(1.3, 2.7)*Power(kappa, 2.0) + Complex(0.3, 2.0)*Power(kappa,5.0)*log(alpha) The file is extremely long (many tens of ...