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

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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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regex matching with “locate”

I'm trying to use the locate command to find files in my home folder, however whenever I try and run this I get no results: locate -i -l 4 --regexp '^\/home\/jack\/[A-Za-z0-9\/\ ]*(My.)*$' I've ...
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391 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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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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638 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 ...
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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 ...
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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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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 ...
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209 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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362 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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643 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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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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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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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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67 views

how to find files based on filename range?

I have some files with numeric names: 2341a.po, 4567211someword.po, 0012.po, etc. I would like to find a set of files based on the numeric range. such as [126 - 363]. Normally I use regular ...
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95 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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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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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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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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454 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 ...
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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 ...
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csplit not obeying backslash r \r as carriage return

I have a file with \r\n line endings (CRLF carriage return line feed). This command works: $ csplit --silent --prefix=email-emailbad.txt- \ --digits=3 emailbad.txt '/^\.^M/'+1 '{*}' This ...
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Rename file in Mac OS Terminal using Regex

Hundreds of images need to be renamed with a terminal command using regex on MacOS 10.9 Mavericks. The files are named this way: 0045AW489R3T(IPCAM)_0_20131124101245_931.jpg ...
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547 views

Expand regex on multiple lines in Vim

I am working on removing comments from a C source file. Let's focus on multiline comments /* ... */ and ignore the inline ones (//) The following command seems to work with (solaris) sed: ...
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How to cut the output to only gather the filename and get-parameter?

I have multiple files with multiple links that are formatted like this: <a href="http://example.com/fnord.layername.html?parameter=FOO-_-BAR-_-FNORD" class="poit"> <img ... /> ...
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regexp in ksh for extensions tgz, tar.tgz

I'm trying to get a regexp (in ksh) to identify files with only the following extensions: tgz, tar.gz, TGZ and TAR.GZ. I tried several but can't get them to work. I'm using this regexp to select only ...
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parsing through log file and printing out regex backreferences

I want to parse my /var/log/maillog to print out the email addresses in "from=<>" and "to=<>" (mainly to do a quick check for false positives in the DNS RBLs that I've configured) A maillog ...
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1answer
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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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121 views

To write this Pseudocode with Regex

I am doing a Makefile which I run regularly by Crontab every day at 0230 crontab -e; 30 2 * * * /bin/thePseudocode Python-like Pseudocode directories = ["Cardiology", "Rheumatology", "Surgery"] ...
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bash: regular expressions in if expression

In my script on my ubuntu machine I declare a string like this: DEBUG_PACKAGE_LIST=$(apt-cache search dbg | awk '{ print $1 }' | grep -e "-dbg") For you to help you understand my problem here is ...
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How to match a particular form of optional sequence from a manual synopsis, including variations?

In this Q&A there is a reference to the manpages synopses being based "loosely" on the Extended Backus–Naur Form of metasyntax notation. It's interesting and serves as background. That being said, ...
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procmail recipe with a regex doesn't work

In my ~/.procmailrc I have the following lines: :0 \* ^Subject:.*(O|o)pen( \|)(S|s)(onic|urge) $MAILDIR/OpenSurge/ As you see, I would like to put any mail containing “Open Surge” (or any variant ...
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Using regular experision in “rpl” command

I need to replace text in lots of files. I'm using rpl for this purpose, but I can't find any way to make it use regular expressions. Can rpl use "regex"? how? Edit: I'm using rpl 1.5.2 from Ubuntu ...
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rsyslog: make %syslogtag% equal length

I have rsyslog configured to log in the following format: $template long-iso,"%$NOW% %timereported:8:15% %syslogtag% %msg%\n" which produces logs like this one: 2013-12-14 15:59:39 ...
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1answer
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Using BASH versus ASH on Synology

The majority of my photo files have the following naming convention / format IMG_20131204_120000.JPG, showing date and time the photo was taken (iPhone/Apple naming convention). However, not all my ...
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1answer
192 views

Regex to find NFS filesystems that aren't being mounted with nosuid, except for ones with special needs

I have a script that runs the command mount -v 2>/some/file, which I then parse with another script using the following regex: ^.*[\ \t]+type[\ \t]+nfs(?![\ \t]+.*\b(?:nosuid|nosetuid)\b).* The ...
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Alternative regex for {}

I am trying to replace all of this line, but the numbers: looktype="123" so only the numbers show up. Is this possible in any easy way? {sub ("look type=\"[0-9]{0,3}", "TEST")} I am trying this ...
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Why is this line included in the `logcheck` report email?

In addition to the Debian provided rulesets, I have added a file /etc/logcheck/ignore.d.workstation/wpasupplicant.local (owner root:logcheck, mode 0644) to my newly installed logcheck setup. I have ...
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192 views

How to negate a regex inside another regex

That is, given a POSIX regex X, what POSIX regex is the complementary of X? (in a more detailed way: how to get regex X' that matches all strings that are not matched by X, but doesn't match any ...
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538 views

Parse apache logs to exclude IP ranges

I need to look for some requests in a huge pile of apache logs. My only requirement is this: I need to only view the requests coming from any IP address that is NOT included in a list of 50 IP ranges ...
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4answers
926 views

Change currency format to generic number using sed

I am working on a large csv file with all coma separated entries. The entire document is composed of plain numbers, except for a few columns reflecting currencies that are formatted as text. For ...
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1answer
344 views

Why doesnt ctrl+d work with this?

I wanted a simple way to process text in my clipboard without having to create a file. I tried using the following line: awk '{print $1}' <(cat) but I couldn't send cat the EOF character using ...
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regex replace text in xml file within node from the command line

I have an XML file and I would like to replace everything that is between the open and closing tag within multiple instances of the g:gtin node with nothing. Is this possible from the command line, ...
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Match one part of a regular expression in a Kwrite find-and-replace regex

Among the joys of KDE, Kwrite is surely noteworthy. Having regular expression support built in by default into text editor is probably one of the top 10 best ideas of all time. Since I often need to ...
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perl regex replacing globally when global not selected

I'm using Ubuntu 11.04 and wrote a small script that searches within text files for certain "tokens" and replaces with some a prewritten snippet from a template file of the same name. The text files ...