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

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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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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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39 views

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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558 views

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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91 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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1answer
252 views

How to insert both vimscript variable and string into vim search and replace

I've only just found out about Vimscript's existence as of today, so forgive me if this question is more basic than it seems, but I've been struggling to find an answer to this question for the better ...
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1answer
99 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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421 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
590 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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241 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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2answers
246 views

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 ...
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4answers
303 views

regex to match identifiers without double _

I want a regex to match identifiers consisting of letters, digits and _, without double underscores. My current attempt: ^(?!_)(?!.*?_$)[a-zA-Z][a-zA-Z0-9_]+$ Example: Abdfsdfsdf__ 1B2345_ ...
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618 views

Regex for phrase matching with case statement in ksh

I am trying to start or stop a service on AIX in ksh. I am trying to start to build in fool proofing for checking things like if the services is already down, etc. Here is my script #!/bin/ksh ...
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Replace the shortest match of a string pattern

I have this string: update mytable set mycol=myvalue where mycol=yourvalue; I need to convert it to: insert into mytemp select * from mytable where mycol=youvalue; I can accomplish it like this ...
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491 views

remove trailing zeros in awk not working. syntax error

regex = "\\.*0+$"; subst = ""; system("echo "id "| awk '{sub(\\.*0+$," subst"); print}'"); It is giving the following error: awk: cmd. line:1: {sub(\.*0+$,); print} awk: cmd. line:1: ^ ...
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937 views

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 block the Google Analytics Script using Privoxy

Related subject: Privoxy: blocking twitter, facebook and google outside of their domains + HTTPS Never mind what rule I am adding to the default.filter file, I don't make it to block these scripts. ...
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lookbehind and using it with grep in Vi?

Trying to get into Vi (not Vim), after learning Vim. Vim has a lookabehind like /\(Not this\)\@<!$, how to do it in Vi? If I want to search recurvively down directory in Vim, I could do :vimgrep ...
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Regex `/pattern/g` and ed `:g/pattern/`: which came first, and why `g`?

The g option (e.g. s/pattern/replacement/g) for many tools that use regex-style pattern matching and the :g command in ed/ex/vi/vim have pretty similar usage and meaning: match the given regex ...
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229 views

lftp exclude syntax confusion

I am confused with the syntax description given for lftp from their website: -x RX, --exclude=RX exclude matching files -X GP, --exclude-glob=GP exclude matching files How ...
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348 views

Regular expressions with ExpectJ

I've been used the ExpectJ Java library to automate some jobs on a Linux server, however now I need to automate a job that sends a different text response for each execution. Here is the output: Last ...
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(Mac Terminal) sed to parse JSON … what am I doing wrong?

In Mac Terminal, I'm trying to parse the "name" out of this JSON response: {"created_at":"2012-08-27T20:04:27Z","deleted_at":null,"id":21462840,"item_type":"video","name":"CastingBy-v12 ...
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119 views

Check some property for every line of a file

I have several (427 to be precise) text files with a million lines each containing 31 numbers separated be spaces (possible double spaces). However there might be some data corruption and there may be ...
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60 views

How can I reformat tabular data using AWK?

I have a file contain following output. ora.abc.db 1 ONLINE ONLINE serverA Open 2 ONLINE ONLINE serverB Open ora.xyz.db 1 ...
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107 views

Why `rename` behaves differently whenever I use full path instead current path?

Ok, I'm answering a question where the OP have several repositories in Ubuntu that might be causing a problem installing unrelated software. I recommend disabling the PPA's using a single liner rename ...
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757 views

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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54 views

Stuck in separating chars into strings in my approach. Found a working approach but can not understand it

I am trying to figure out how to break a string to be on character per line. I.e ahebhaaa to be: a h e b h a a a I tried: $ echo ahebhaaa | sed 's/\(.\)\(.\)/\1\n\2/g' I.e. my ...
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Print lines where first field has only four characters using regex in awk?

John Goldenrod:(916) 348-4278:250:100:175 Chet Main:(510) 548-5258:50:95:135 Tom Savage:(408) 926-3456:250:168:200 Elizabeth Stachelin:(916) 440-1763:175:75:300 output should contain the lines ...
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grep equivalent of the kwrite regex [A-Z][A-Z]+

So, it took me ages, but I finally learned to think in terms of regular expressions, thanks to using them in kwrite. But I still don't know how to translate that knowledge to grep. I love my grep, ...
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911 views

Difficulty making a regular expression to find at least 2 occurrences of a character in a file

I have a file containing random codes. Each code has ten characters in it, and I am trying to grep codes in the file that have at least 2 occurrences of a character. I am doing this: grep DD* ...
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Using grep to match only a match group in a regular expression?

I need to set my keyboard layout with setxkbmap before launching Wine games, as I use Dvorak for typing and this breaks every game's controls. What I'd like to do is simply write a script that grabs ...
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Escaping * with Regular Expressions and Grep

I have a file that has unique lines that start with 2 stars (**). However when I run a grep command for grep \*\* fileName I get all of the lines in the file. This is very unusual, and what I ...
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383 views

Trying to remove all ids from an HTML file with grep

I'm trying to remove all id=" "s from an .html file but I'm not sure where I am going wrong. I tried using regular expressions but all I am getting is the .html file rendering in my Ubuntu terminal. ...
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Regular expression problem(s) in Bash: [^negate] doesn't seem to work

When I execute ls /directory | grep '[^term]' in Bash I get a regular listing, as if the grep command is ignored somehow. I tried the same thing with egrep, I tried to use it with double and single ...
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678 views

Differing outputs of the commands “ls .*” and “ls *.”

The command ls .* when run gives as output the following : All the files in the current directory starting with a . (hidden files) All the files in the hidden directories present in the ...
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58 views

Pattern repetition and regexp

Take the pattern [UGLER]* Can the string UUG match against it? I mean to say, is repetition allowed?
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275 views

grep for an alphanumeric strings of any length with a colon on each side

How would you grep for an alphanumeric strings of 1 to 50 characters (ideally, any length would work too) with a colon on each side – a typical result would be all the lines containing the string ...
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604 views

Using grep command and backreferencing

This is a pretty basic question, but I can't get my head around it. I'm learning Linux and one of the questions i've been given is; *The word sentimentalment includes the same three characters ...
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460 views

Weird zsh grep -P behaviour

I connect to server with PuTTY from Windows. I have a long yet not touched (I suppose) by hands of local admin config: $ cat /opt/jira/.subversion/config ... ### must be enabled, which is ...
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481 views

What does this egrep command do?

What does this egrep command do? egrep '[^A-M][0-9]+' /etc/passwd So far I think it searches for any file in /etc/passwd that starts with A-M and includes the number(s) 0-9. Is that right?
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What does the dot in regex “^[A-Za-z]{2}[1-9]{2}.*” do?

I am very new with regexp. I would like to know the pattern defined by this regexp : ^[A-Za-z]{2}[1-9]{2}.* It starts with 2 alphabetic characters then 2 numeric characters then a . and * which is ...
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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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use search result in replace statement with vim substitute

I know this is gonna be a stupid question, but I've tried here, google and the official documentation. I've got a file with a whole heap of words of the form 'foo' and i want to change them to ...
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139 views

What does this regex mean?

I was working on the conversion of Unix newline to Windows newline. I tried to unix2dos but it gave me some binary error, so I looked it up and stumbled upon this regex sed 's/$'"/`echo \\\r`/" ...
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Grep and regex, Why does the following return only a specific portion?

Why in the following: echo this is a line. | grep -o -E "[a-z]+\." The result is line. and not this is a line.? There is no word boundary or any other restriction on the regex.
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164 views

Regex and piped commands with sed

I'm finding really hard to use sed command, plus I can't seem to find well written tutorials. Let me say that I worked with regular expression in other languages (Python, JavaScript, Java), so that ...
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50 views

Regular expressions help

what the different between these two regex expression ? AB\{4\} and (AB)\{4\} for the first expression I think that it repeat B 4 times, then for second expression it repeats AB 4 times. When I ...