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

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Match multiple regular expressions from a single file using awk

I'm trying to parse a HTML file using shell scripting. There are 4 different regular expressions that i need to catch: name= , age= , class= , marks=. Using grep "name=\|age=\|class=\|marks=" ...
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Find all characters “[1-777])” at the beginning of the line

Pseudocommand perl -pe 'g/^[1-777])/g' data.txt where I try to all numbers at the beginning of a line with ")" following them etc 1), 67) and 777). Data where all question numbers should (etc 1), ...
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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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grep: display filename once, then display context with line numbers

Our source code has error codes scattered throughout. Finding them is easy with grep, but I'd like a bash function find_code that I can execute (eg. find_code ####) which will provide output along ...
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How to replace text between two markers in a file with a section of text from another file?

Say I had a block of text in the ~/.bashrc: #~/.bashrc # ...some commands... # aliases alias suicide='sudo rm -rf /' # end aliases # other commands I wish to replace that block of text with some ...
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Why do I have to escape a “dot” twice?

I know that we can escape a special character like *(){}$ with \ so as to be considered literals. For example \* or \$ But in case of . I have to do it twice, like \\. otherwise it is considered ...
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Lowercase all but the first (Uppercase) letter from UPPERCASE in cyrillic

To make all letters a lower case except the first letter. The first letter would look like "Uppercase" after I changed (from UPPERCASE in cyrillic). The rest (not UPPERCASED) leave unchanged. I'm ...
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How can I find and replace only if a match forms a whole word?

My script is: n="y" while [ "{n}" = "y" ] if [ $n == "n" ]; then break; fi echo "n is $n" do read -p "Enter the word to find = " word read -p "Enter word to replace = " replace ...
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2answers
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BSD sed: Replace only the Nth occurrence of a pattern

Using BSD sed; How can I perform the following substitution?: Before: hello hello hello hello hello hello After: hello world hello hello hello hello In other words; how can I replace only the ...
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1answer
379 views

Trouble with grep -o regex

I'm trying to use a grep command with the --only-matching flag, but it's not behaving as I would expect it to. This command: echo "1/2/3/4/5" | grep -oE "^([^/]+/){0,2}" Gives this output: 1/2/ 3/...
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Is there a tool in linux that allows multi-line regex expressions?

I'm wanting to find the results of a multi-line regular expression in linux. I tried grep, but like most linux utilities it's line based. Is there something similar that allows me to search across ...
4
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1answer
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Bash regular expression pattern matching spaces, within double brackets test, using “~=” operator

Simply said, I just can't find a way to match a variable against some pattern containing spaces. Here is what I expected to work (echo 'ok' string) item='foobar baz' pat=".+bar baz" if [[ "$item" =~ ...
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Find and regex

What am I doing wrong with this find expression? ; touch ook ooks ; find . -name 'ook' -or -name 'ooks' -type f ./ook ./ooks ; find . -name 'ook[s]?' -type f [returns nothing] ; echo $? 0
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1answer
459 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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3answers
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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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3answers
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sed - how to (not) match unmatched brackets

How can I do my operation only on lines that close their brackets? For example I want to change ".is" lines and add a bracket but not for lines with unclosed brackets. so these are changed ...
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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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1answer
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How to grep exact word with only space as word separator

For Example: I have file like following: AA ABC-AA-AA AAA ABC-AA ABC.AA ABC AA ABC.A AA If I use grep -w "ABC" file1, I am getting all the lines. But I should only get 3rd line: ABC.AA ABC It is ...
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2answers
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Insert “return 0” between all braces in a file?

I'm setting up a fairly large (~50 functions) test library in C++. I forgot that the functions have to return integers. I actually forgot to put a return type at all, how dumb is that? I added the int ...
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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 ...
2
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1answer
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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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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 ".*/mypackage-([a-zA-Z0-9.]+-[0-9]{1,2}...
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“bad flag in substitute command: '{” while replacing a string with sed from one file to another file

I am trying to replace strings found in File1 with strings in File2 File1 <IMG SRC="/Repository/GetImage.dll?baseHref=Orange/2011/03/27&amp;EntityID=Ad12911&amp;imgExtension=" /> <...
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2answers
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how to replace a sed expression (change and print only matched line) with a perl expression?

I am trying to move to perl (from sed). But how can I replace this sed expression with perl in a similarly short way? sed -n '/patternmatch/s%stuff%changed%p' file I need to search for a pattern, ...
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how to replace a sed/perl expression (change and print only matched line) with a python expression?

I have asked this question to learn how perl could replace sed. Now I want to know how the following commands (which do the same thing) would look like for python: sed -n '/patternmatch/s%stuff%...
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1answer
135 views

How can I use regex to extract the text following two conditions into a variable?

I'd like to extract a setting for a given host in the ssh_config file and put it into a variable. Host mysite HostName 123.1.1.1 User myuser Port 13245 GSSAPIAuthentication no ...
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1answer
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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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3answers
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How to print only the first match with grep

I'm trying to grep username: users | grep "^\b\w*\b" -P How can I get it to only show the first match with grep?
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1answer
2k views

How to highlight the whole log-line in color with multitail

I'm trying to use multitail to tail logs with color highlights. I defined a custom color scheme in multitail.conf, something like this: colorscheme:my-color cs_re:red:^\[E cs_re:yellow:^\[W cs_re:...
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Curl and grep html text

Is there a way to grep html text from a curl request and output grab the value that is between two html tags? More specifically the input value of a form?
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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 ...
0
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1answer
175 views

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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1answer
245 views

Replacing all `&` but not the one in XML entity `&amp;` with `#` with sed in a given XML tag

I needed to replace all & with #, inside and only inside the <faultstring> ... </faultstring> tag. Additionally, the & in &amp; should not be changed. Sample input: 123&&...