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

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What does ^> mean in a grep pattern?

What does this command do? grep "<[^>]*>" inuux.xml What is searching for?
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AWK print regex pattern

I am trying to print a regex pattern for the following piece of mail log. In particular I am trying to get the ID between the square brackets (see the second line for reference). Mar 29 03:48:13 ...
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How to extract the similarities between two strings

I have two strings in two different sentences: string 1: 30 mutation alanine for valine string 2: alanine at position 30 is there away to find the similarities between them as it is clear they ...
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To remove \n but not \n\n

Data 23. Lorem A) he B) ha C) hu c 2. Ipsun yes right to write something here? A) Ok B) No C) yes b 292. Ipsun A) Apex B) hello b 289. He A) hu B) Ha C) He The right answer is: 1) Ab 2) Abc 3) ...
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Bash Combine Replacement and Sub String Extraction in One Step

For a string in this format: ./my-site.sub.domain.com I would like to remove the .,-, and /, and trim the remainder to 16 characters: mysitesubdomainc I've done this ...
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How can I use grep to search a file for string combinations?

What I'm trying to do is use grep to search my Apache logs. What I want is to find is every entry from a certain IP address that also has .html or .php in the line. In other words, I want to see what ...
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grep + operator

According to the grep manual: * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. Let's test it echo 'agb' | grep 'a.*b' # returns ...
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Why does this regex find a match for \x63 with a pattern [\80-\BF]

I am trying to filter valid/invalid UTF-8 bytes, but I get strange results from the following regex (which is intended to handle a 3 byte form of UTF-8). I have intended the pattern should not ...
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Vim: Substitute based on another match in the line

I have rather large files in which I need to substitute NX for N1 but only if the line already contains NX as a pattern. So far I do it manually by first searching for occurrences of NX with: /NX ...
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grep log lines of a specific id request

So, I have the following log sample: 2015-03-30 10:19:44,200 DEBUG [Default : 1] [Application:ABC BIW: IDA:6d87de8e-1276-4496-b49d-dd4cd375cbe4 Info:P23 Code:ABCD] A log message 1 2015-03-30 ...
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Simple way to extract value from HTML

I have a very simple html file with a value inside. Value is 57 in this case. <eta version="1.0"><value uri="/user/var/48/10391/0/0/12528" strValue="57" unit="%" decPlaces="0" ...
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Regex to grep filler followed by signed float

I want to extract the last column from lines that look like: 880.952 NAV_Y uSimMarine -146.17516 The number isn't always negative, and isn't a fixed length (i.e. doesn't ...
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Use grep with or [duplicate]

How do I search in a textfile with grep for the occurrence of a word or another word? I want to filter the apache log file for all lines including "bot" or "spider" cat ...
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bash - reading user variable into bash script grep

I've tried every possible combination to get this bash script working. It's part of a larger script, and it basically prompts for a username (to check if it exists) and returns the appropriate ...
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Asking ls to only list files in a path that match a specific glob/regex

In Zsh: Is there a way to use ls to only list files and folders in the current directory that match a specific globbing or regex pattern? For example, say I have multiple files that start with the ...
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How to use variables in substitution with vim regular expressions

I have a big file that contains among others serveral lines of the following form: USet07-1 USet07-2 USet08-1 USet08-2 . . . USet22-2 . . . I want to remove the hyphen/dash - from these strings in ...
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effect of [0-9]* in a regular expression

What is the function of [0-9]* in the following statement, which will write all lines that start with an even number, followed by a space, to the file even: sed -n 's/^[0-9]*[02468] /&/w even' ...
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What regular expression in grep searches for strings of three same letters in a row?

I have a text file and I am using the grep command with a regular expression to get only the lines which contain three same successive letters, e.g.: aaa bbb ccc ddd What regular expression do I ...
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To match only innermost environment by Regex

I want to match the innermost environment of begin{question} and its corresponding end{question}. Example data \section{Takayasu arteritis} \begin{question} {You get a patient. What do you notice ...
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Finding all kinds of extensions referenced in a html file

Here is my problem statement : There is a folder with many html and text files. I need to recursively go through each one of them and find all kinds of file extensions referenced in these html/text ...
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Regex and patterns on a ksh command line

I'm wondering what's the difference between using * and .* in a regex string. I guess, * stands for "0 to n characters" but I don't see what .* stands for. For example, what is the difference ...
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How to ask for specific parameters with grep?

I need to look in /usr/share/dict/words for a 5-letter word that starts with d or D, followed by a lowercase vowel, and ends with s. I have tried everything but to no avail.
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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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regex suggestion

echo "223255/12345678 " | grep '[0-9a-zA-Z/\-\?:\(\)\.,"\+]{1,34}' According to the regex, it can have any of 0-9 a-z A-Z / - ? : ( ) . , " + of upto 34 chars in any order. Am I ...
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How to replace multiple occurrences of a pattern with sed

I use the following command to remove surrounding spaces between array keys that are strings or integers in PHP files: sed -ri "s/\[ ([0-9]+|(\x27|\x22).*(\x27|\x22)) \]/[\1]/g" file.php I thought I ...
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To improve this regex about digit separation

Code m/([+-]?\d+\.\d+)[\s\t]+([+-]?\d+\.\d+)/ Data 22.585698 3601.767090 D:\measurements\LabCourse_2015\6\90deg\image0001_23_mT.png 20.051883 3580.268555 ...
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Bash detect ascii art [closed]

For bash script, is there a easy way to detect if a text contains ascii art? An example of ascii art:
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Using regular expressions to search a word list. Finding 2 letter words instead of 3. Why?

I am studying regular expressions and I am stumped. Here is my process so far.... I downloaded this file. wget http://www.mieliestronk.com/corncob_lowercase.txt mv corncob_lowercase.txt words.txt ...
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What is the meaning of (^| )ABC( |$) as an extended REGEX ?

I came here across the command grep -E '(^| )ABC( |$)' file1 I am confused how to interpret the regular expression therein, because I know the ^ and $ character as beginning and end signifier, but in ...
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How to find with grep lines that end in a certain string?

I know that to find a REGEX that ends in a certain string I have to write "string$". Although I tried the following variations of grep : cat foo | grep "string$", cat foo | egrep "string$", grep -E ...
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Using sed to remove digit separation commas enclosed in quotes and quotes itself from CSV? [duplicate]

How can I can use sed to remove from before-last column the group digit char comma and quotes itself? Please note that in the sample below the target column is not contained in double quotes. ...
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Regex gone Wrong

I am using a Bash script to use awk to look for this: (0010,0080) The awk will generally look for any numeric value seperated by a comma in between parenthesis. I have done everything I can think of ...
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Strip the file base name, keep the directory part

I have a string which looks something like this dir/subdir/othersubdir/file.txt But it can also look like dir/file.txt or dir/subdir/file.txt Now, I am making a script where $P is the full ...
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Grep finding phone numbers in files

How would I look for files in the /etc directory (but not subdirectories) that contain a standard United States long distance phone number, written using the pattern of 1-###-###-####, where each # is ...
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Expansion of *,#,% - What do they mean? [duplicate]

for j in * .* ; do cp $j ../$name-S$i.gid/${j%%. * }$i.${j#*.} done Could someone tell me what this for loop does? What do *, % and # mean? ($name is a path of a directory in which there are ...
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Grep lines from foe to foe2 (not included), regexp

The file is organized in entries of the form: foe, 1.... 2.... 3.... foe2, 1.... 2.... All sub-items begin with four spaces, and then text or number item. All entries like foe, begin ...
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How do I join the next line when a line matches a regex for whole document in VI?

As title, for example, I have lines like abcdefg join! abcdef no join abcdefg join! If a line matches regex ^a.+g$ then I would like them to be joined, so it would be: abcdefgjoin! abcdef no join ...
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sed how to do “or”

I have the following two lines that work ok: /\.to <\=/ s/<\=/be <\=/ /\.to_not <\=/ s/<\=/be <\=/ I would like to combine them and I tried: /\.to( |_not )<\=/ s/<\=/be ...
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Replacement in VIM with regular expression matched part unchanged

Suppose I want to append two digit numbers in my file with "some_thing". Like from this: 12 23 45 to 12_something 23_something 45_something How can I do this using regular expression ...
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What characters should I escape while modifying a file using sed? [duplicate]

I am using the following sed command(with word boundary): sed "7 s/\<<Filevalue=.*/>\>/<Filevalue="true"/>/" < config.xml And I am getting this error: sed: command garbled: 7 ...
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Filtering Log Output on Separate Lines

I did a recursive grep in a directory to find all files that would match as follows grep -ER "match_string1|match_string2" /path/to/dir/ What I get as output is: ...
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Vim: Count all occurrences (including multiple on the same line) of char or word

I try to count all occurrences of a char or word in a file with Vim. This means multiple occurrences of the same word in the same line should be taken into account as well. This has been discussed in ...
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Interactive less search with wildcards [duplicate]

I'm using less to view a large file and I want to search for a pattern with wildcards — e.g., " x 1??" where ? is any character. Does less support that, and if so how would I do that ...
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How to search parenthesis by ack

I want to search for a parentheis ( using ack, but neither using ( nor \( worked. The first one ("(") is recognized as a multiple line command. The second one ("\(") is treated as an invalid regular ...
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What is the Difference between Regex `[]*` and `[]+`?

I started learning regex recently. I know that * modifier means match 0 or more times while + modifier means match 1 or more times. However when you use these modifiers with square brackets, how ...
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regex find replace strings starting or beginning with backslash

I have a compilation album in my music library that has song titles in the form of ARTIST/ TITLE, which is making it really difficult to cp or mv these files because of the slash. So I'd like to ...
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Regex long list of numbers

What is the command in Linux to find the regular expression e for every number from 37 to 200 included in a list with such numbers?
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How to escape unbalanced brackets or slash in sed?

I'm trying to use sed, but my pattern contains [] brackets and slashes (/). I've tried quotes, but it doesn't help. How do I escape it? Examples: $ sed -i'.bak' "s/^includes[] =/;includes[] ...
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Shell pattern matching vs. regular expressions occurence [duplicate]

I am relatively new to Unix, and I stumbled across one curiosity. Some shell constructs like case or find, employ pattern matching, but it is not quite regex. Other commands, like ed, sed, vi, and ...
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Print text between tags (inclusive) if certain text is found

I've got a task to extract data from several Apache servers. The task is to print out: <Directory ...> ... </Directory> where +ExecCGI is located within. Let me give an example to ...