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

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How to match Markdown Setext headers in in exuberant ctags

I am working on a language definition for pandoc markdown in ctags. However, I have problems matching Setext headers in the regex which obviously are defined by multiple = or - in a new line under the ...
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1answer
166 views

How can I grep two things where one has option -w?

I have a json file from where I want to get the value of two items which are in an array using grep. Let's say I'm trying to get data from values foo and bar, the problem is that baralso matches ...
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7answers
64 views

Rename files add dashes after fourth and sixth characters

I have some files such as: 20150716_something-here 20150716_something-heretoo 20150716_something-hereaswell They need to be renamed as 2015-07-16_something-here 2015-07-16_something-heretoo ...
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3answers
649 views

How do you remove dot character from string without calling sed or awk again?

I have a file called hostlist.txt that contains text like this: host1.mydomain.com host2.mydomain.com anotherhost www.mydomain.com login.mydomain.com somehost host3.mydomain.com I have the ...
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2answers
35 views

grep for single quote and double quote in a string

so i am trying to write a grep which finds the .epl file names or file paths in a given file. I have tried the follwoing regexs Part 1 : REGEX Used grep -rEco "/(.+).epl|(.+).epl" ./index.epl Result ...
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Exploit in bash script parameter possible?

I want to pass an e-mail address from a web form to a bash script. I'm using the following regex: /[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}/ Is this sufficient? Or could one embed an ...
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2answers
21k 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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2answers
61 views

Credit card number validation with bash

I have used the following regular expression to detect the valid card numbers. [2-6][0-9]{3}([ -]?)[0-9]{4}([ -]?)[0-9]{4}([ -]?)[0-9]{3,4}([ -]?)[0-9]{0,3}[^a-zA-Z] But it does not detect the ...
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1answer
86 views

LFTP exclude file extensions

I am trying to mirror directories with lftp but I don't want to download filetypes that are notoriously large like .mp4 and .swf. But I am having trouble with the regex - and seeming like the ...
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2answers
4k views

Pages don't get blocked with Squid over HTTPS

I have set up Squid to block pages on my own system (i.e not on a network), and I'm trying to get SSL to work with page blocking. To this end, I've set up ssl-bump and installed the certificate to my ...
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How can I parse an ini file whose values may contain certain characters?

I have looked at a couple bash ini parsing scripts and I've seen this one used a few times here so I'm trying to see if it will work for me. It looks like it reads the ini file line by line multiple ...
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50 views

Command line tool for easy multiline regex search and replace

I use PCRE regular expressions for search and replace very often when working with a text editor and I was left quite unhappy after I found out that in powerful Unix command line tools like perl, awk ...
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1answer
24 views

Card Number regular expression help [closed]

I have used the following command+REGEX to list all the files contain card numbers in a set of files. grep -r -l -e '[3-6]\d{3}([\ \-]?)\d{4}([\ \-]?)\d{4}([\ \-]?)\d{3,4}' * I have tested this ...
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1answer
27 views

how to find and delete certain regex in geany text editor?

I have a sample text like this: \documentclass[a4paper]{article} \usepackage[a4paper,margin=2cm]{geometry} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{color} ...
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1answer
31 views

Can anyone explain in detail the following two commands regular expressions

The following two commands used to count no of non-zero integers of second column in the text file. Can anyone please explain the regular expression in detail. grep -c '^[^,]*,[^0][^,]*,' < ...
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686 views

Using regex to get mouse MAC address

What would be the most handy way to grab the mouse's mac address from the following output: ~ ➜ bt-device --list Added devices: Logitech K811 (00:1F:20:EB:06:E0) Plattan ADV Wireless ...
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291 views

Remove files by regular expression

I want to keep files whose names match [0-9A-Z]{1,2}_\d{4}_\w+?\.dat, for example, A1_2001_pm23aD.dat, K_1998_12.dat, and remove the rest. However, the ls and rm commands do not support such regexes. ...
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5answers
5k views

Print line after nth occurrence of a match

I am looking to display the line 4598 in the following file. Effectively I want to display the line AFTER the nth occurrence of a match. In this case, the line after the 3rd occurrence of <Car>. ...
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2answers
42 views

How to get numbers of specified (range of) length from string with grep?

Here I have a bash "one-liner": cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 16 | grep '[0-9]', which generate 16 lines of 16 character alphanumeric strings. Example of output: ...
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1answer
39 views

Replacing mysql settings with sed

I am creating a backup web server but I want the backup server to only have one root user. So after moving all the databases I need to replace all the mysqli_connect(...) lines in db.txt. I have ...
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8answers
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How can I use sed to replace a multi-line string?

I've noticed that, if I add \n to a pattern for substituting using sed, it does not match. Example: $ cat > alpha.txt This is a test Please do not be alarmed $ sed -i'.original' 's/a test\nPlease ...
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Regular Expression for finding double characters in Bash

I am looking for a regular expression that finds all occurences of double characters in a text, a listing, etc. on the command line (Bash). Main Question: Is there a simple way to look for sequences ...
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3answers
189 views

sed regular expression behaving differently than in vim and perl?

Here's a sample 'test.txt' abcdX1yad45das abcdX2fad45das abcdX3had45das abcdX4wad45das abcdX5mad45das sample desired output: X1yad X2fad X3had X4wad X5mad I could get it working in vim with: :% ...
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Regex that would grep numbers after specific string

So I have a line: ID: 54376 Can you help me make a regex that would only return numbers without "ID:"? NOTE: This string is in a file.
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36 views

Using grep with the --exclude-dir flag to exclude multiple directories

I am searching through a Ruby on Rails application for a word using grep on OSX, and I would like to exclude directories that match a certain pattern. I am using the following command: grep -inRw ...
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2answers
1k views

Why isn't sed using the extended regex mode by default?

I am using sed. I was using a regex that was correct as far as I could see but sed did not do anything. Turns out that I was using \s+ which sed can not understand (?) and when I switched to [ ]+ it ...
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1answer
194 views

Grep word boundaries

Accorging to GNU documentation: ‘\<’ Match the empty string at the beginning of word. ‘\>’ Match the empty string at the end of word. My /etc/fstab looks like this: /dev/sdb1 ...
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2answers
35 views

Regex in find - OS X

I cannot figure out what's wrong with my regex, it seems to be working with grep but now with find. I'm trying to find all the files which follow the common expression in TV shows e.g. S02E21. find ...
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46 views

Finding special characters in name

How do I find files that have ~ * and other special characters in the name? e.g. find . -name "*\*" should match "any characters" and then *, but it matches nothing; how can I get the command to ...
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2k views

Why does my regular expression work in X but not in Y?

I wrote a regular expression which works well in a certain program (grep, sed, awk, perl, python, ruby, ksh, bash, zsh, find, emacs, vi, vim, gedit, …). But when I use it in a different program (or on ...
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78 views

Pattern matching [duplicate]

I am trying to follow Bash Cookbook to learn about Bash Scripting. I am on example 6.8 Testing with Regular Expression. I have the following script: #!/usr/bin/env bash # cookbook filename: ...
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1answer
50 views

egrep doesn't work as expected on SunOS system

Here is what I want to achieve on SunOS: Only pattern like [text_text=text], [text=text], [text] or text are valid patterns, where by text I mean anything in 0-9,a-z,A-Z, space, newline, tab, enter. ...
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1answer
1k views

Why does `grep fil*` fail?

I found echo file|grep fil* fails, but echo abcd|grep abc* succeeds. I don't understand it, can someone explain? Thanks
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256 views

How to subtract 1 from numbers matched by regular expression?

I'm trying to write a script that reduces each number in line by "1", but I'm getting all "0"s instead: awk '{a=gensub(/([0-9]+)/,"\\1","g",$0); if(a~/[0-9]+/) {gsub(/[0-9]+/,a-1,$0);} ...
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4answers
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How can I extract/parse a complete URL from a semi random string?

I'd like to have bash parse/extract a full URL (and only the url) from a random short string. Examples: bob, the address is http://www.google.com or https://foo.com/category/example.html is up ...
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2answers
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only regular expressions : i want the lastnames that start with A or R [duplicate]

name ,lastname,phonenumber Hace, Apoio, 703-2101 Yoliot, Apostolos, 4222-1124 Jenny,Thano,105-4122 Aeriom,Koun, 510-4122 Dekon, Atolo, 502-2522 Feow, R,685-3431 I did this but doesnt worked and ...
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3answers
95 views

Puppet doesn't ignore whitespace

I have an entry that may or may not appear in /etc/rsyslog.conf: # Added for Kiwi *.err;*.emerg;*.alert;*.warning;*.debug;*.notice;*.crit;*.info @10.19.24.50 Since some of these servers ...
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0answers
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What is the meaning of :- in unix? [duplicate]

Trying to understand the existing script where they have assigned ${3:-} to variable. Script : partition_parameter=${3:-} if [ -z $partition_parameter ]; then readonly drop_partition=false ...
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1answer
29 views

How do I match beginning/end of string in regex?

I know that there's ^ and $ but those are for the beginning and end of line, I am trying to match the beginning and end of string/word. I tried to use \b, which didn't work. For example: echo "lol ...
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2answers
59 views

Use of \$ at end of variable name passed to grep

I was going through one of the shell scripts and found a line: ls $dir | grep -c "$NAME.${var}\$" I understand that $ would expand the variables NAME and var, but is it required to put \$ at the ...
90
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5answers
71k views

Can grep output only specified groupings that match?

Say I have a file: # file: 'test.txt' foobar bash 1 bash foobar happy foobar I only want to know what words appear after "foobar", so I can use this regex: "foobar \(\w\+\)" The parenthesis ...
2
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1answer
21 views

Simple Regex match not working

I have the data below which I am trying to parse out the tittle with each of the following RegEx, Some Entries have a (Year) or other do not. same with the database number. is seem to get different ...
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2answers
3k views

Regexp in .ssh/config

At work, I often have to log into hosts which follow a common naming scheme, e.g. qc01 - qc12, hc01 - hc10, and so on. All of these need to get the same config values in my laptop's .ssh/config. Of ...
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2answers
35 views

Why is this command to open man page and perform search not working? [duplicate]

This open-man-page-and-search-for-string-in-a-single-command question half covers what I'm trying to do: Instead of doing man chmod and then /a+x to jump to the first section in the chmod man ...
3
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1answer
806 views

Aptitude regex engine

I was trying to lookup the versions of libdb in the debian archives with something like that: $ aptitude search '~S~ndev$(~nlibdb~(\d~|-~)!~v~rnative)' which didn't work as expected so I changed ...
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3answers
5k views

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 ...
3
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3answers
769 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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3answers
275 views

Grep exact number of digits and some other characters

I'd like to parse a file containing 5 digit numbers separated by comma or dash, lines like : 12345,23456,34567-45678,12345-23456,34567 My goal is to find lines which have incorrect formatting eg. ...
3
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3answers
48 views

Grep that works with overlapping patterns

I want to count the number of repeating patterns aa in a very big file. So I use the following command: grep -o "aa" ./bwt/dblp.txt | wc -l This works, except when I have a string such as aaa, ...
2
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3answers
57 views

Print up to (and including) the nth occurence of a pattern in a line

Let's say I have multiple lines similar to below in a file. Turbo is a cat. cats are good. cats are not dog. Coco is a black cat. cats are furry. cats are not dog. now, if want to grep all the ...