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

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Collecting network information

I need to collect information about the network usage of each process. Nethogs presents the data I need in real time, I am trying to save the output to a file in order parse it and plot the data. ...
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Finding and removing words beginning / ending with numbers

I have a large file (>10000 lines) that contains one word per line, with a newline character after each word. The words contain no spaces. I'd like to list (or even better, output to a new file) any ...
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Joining certain lines of text together before modifying them

I have a cricket commentary like - 0.3 Richardson to RG Sharma, 2 runs, gentle, non-swinging length ball on off, Rohit seeks to pick it up. Hit high on the bat and spooned over the returning Mitch ...
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Python script to convert adblock list in a forbidden file for Polipo proxy (regex) [migrated]

On my system I currently running Polipo proxy, mainly for adblock purposes. By a search on internet I've found many shell scripts to convert adblock plus lists in Polipo forbidden file format; most of ...
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find command from regular expression

I have question about regular expression. There are two commands. find / -regex '.*[^-_./0-9a-zA-Z].*' find / If I'm right, these two commands should output same results. Because, the first ...
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Sort input file by the results of a regex

I'd like to sort a file based on the results of a regex expression. For example, if I have the following property declarations in Obj-C @property (nonatomic, strong) id <AlbumArtDelegate, ...
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How to print file content only if the first line matches a certain pattern?

I am writing a script, I want to check if the first line of the file matches a certain pattern and if it does then print out the file. How can I achieve this? How do I check for pattern? Is there a ...
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grep: Trailing backslash

I want to do a grep for \resources\. How do I do this? I've tried: grep \resources\ grep \\resources\\ grep "\resources\" grep "\\resources\\" None of these work.
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vim find and replace around a string

In VIM, if, for example, I have the text http://a.com http://b.com is it possible to find all lines (the whole line) and replace it with something before and after it, such as: <a ...
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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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5answers
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ls | grep works doesn't work with ls --color

I'm trying to list all hidden dirs with the following command ls -lhAF1 | grep -E '^d.*[0-9]{2}:[0-9]{2} \.' which works perfectly fine Explanation for Regex: I'm trying to get all rows that ...
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with sed, how can I replace word within a matching line?

I am trying to write a sed expression to detect lines similar to this: s0:12345:respawn:/sbin/agetty -8 -s 115200 ttyS0 linux and replace the ttys0 with something_else I do not want to detect ...
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scp a file to multiple folders

I wanted to scp file.txt to remote box my-remote-vm-1 In my-remote-vm-1 there are two folders conf-1-ver-2,conf-2-ver-2. The integer part in the folder name can go from [0-9]. What would be the best ...
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Postfix: Remove References to Server Software

Every time my postfix servers sent emails at the destination the emails headers include the following: by suppaserver.example.dev (Postfix) with ESMTPSA id 79D412E1A3A How can I remove the ...
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syntax of ls --hide= and ls --ignore=

ls --hide and ls --ignore provides the possibility leave out files defined through regular expressions set after the --ignore= part. The latter makes sure that this option isn't turned off via -a, -A. ...
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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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How do I replace this pattern with a newline inside it? [duplicate]

If I have a text file with this content: someline <!--\ file first read on 2015/01/11 And I want to delete <!--\ and everything until what comes after "on", how do I do it? The ...
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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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backreferences in `rename` regex

I have A LOT of files named "bar_foo.txt" in a directory, and I'd like to rename them to "foo_bar.txt" instead. In sed and vim the regex to to this would be something like ...
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1answer
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cshell alias: How to use nested single quotes(') in in cshell alias

I am trying below alias in cshell: alias sll 'ls -l \!* | grep -oE '[^ ]+$' | paste -s | xargs ls -l' For this CSH says, Illegal variable name. If I use \$, alias will be set without any error. ...
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How do you save a complex regex for multiple reuse in sed?

In using sed, I often create rather complicated and intricate regexes that I need to match twice in a file. Is there a way for me to save this regex and just reference it twice? Maybe something that ...
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Complex sed Command for Insert Command [migrated]

I have a bunch of php files which have many insert commands. In each query i want to insert a coloumn variable admin_id = '$admin_id' i.e. if the query is insert into users (ch_id, num_value) values ...
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What does [[.ch.]] mean in a regex?

Alternate title: What is a "collating sequence" or "collating element" in a POSIX-compliant regex? I found the exact technical definition in Section 9.3.5 of the POSIX specs, as item #4 in the list, ...
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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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grep content between two starting bracket

Below is file output that I want to access [1] RsyncCommand: 0 Number of files: 18 Number of files transferred: 0 Total file size: 24.01M bytes Total transferred file size: 0 bytes Literal data: 0 ...
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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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How to use find command to search for multiple extensions

I can get all jpg images by using: find . -name "*.jpg" But how can I add png files to the results as well?
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Simple sed replacement of tabs mysteriously failing

This ought to be really simple, but for some reason it is not working: sed -i.bak -E 's/\t/ /' file.txt Instead of replacing tab characters, it's replacing t characters. I've tried every ...
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perl: Replace string in file with double quotes

Following up question from http://unix.stackexchange.com/a/254637/18887 I have the following string in a bash variable This rule forbids throwing string literals or interpolations. While JavaScript ...
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2answers
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sed to match pattern between matching curly braces

From a pattern such as [string 1]{string 2} I want to extract string 2, the string between the last pair of matching curly braces -- that is delete [string 1] and the open { and close }. My ...
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Substitution with Regular Expressions in gedit

Say I want to remove all digits from a text file using gedit 3.10.4 advanced_find 3.6.0 I have selected the Advanced Find/Replace plugin to support regular expressions out of an internet search. ...
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Regular Expression to match (not x) and y (!x & y)

I received a desktop day-to-day calendar with puzzles. One such puzzle was deciphering a quote where the letters were substituted with symbols. I used some RegExs to find longer words, then used the ...
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Complex sed Command with AND/OR/NOT

I have a bunch of php files which have many select commands. In each query i want to insert a coloumn variable admin_id = '$admin_id' i.e. if the query is select * from users where abc='xyz' and ...
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109 views

regex matching and substring extraction

I have these files, manually created by many different people are coming in. Formatting, although following a certain rule, is not uniform. think of these three lines below ...
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1answer
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Replacing in files with sed using regex

i want to replace a string in many files like "Total:*points" using sed. I simply don't know how to use sed with regex. Below is what i got. Thank you in advance! find ./ -iname "skp-corr-*.txt" ...
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Why doesn't this find command work? Regex & Find variants for .mp3 .wav and .m4a files

2015.10.25 Move on and Be Blessed.wav dummy.m4a 2015.11.17 BS Full.wav.mp3 2015.11.17 BS MOL.wav.mp3 find . -name '*.mp3' -o -name '*.wav' -o -name ...
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1answer
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grc: Highlight capture groups only?

Recently I came across grc and I find it really simple. However, I would like to highlight some chunks of regex-matched text. For example, svn status properties conflict highlight I hoped to work: ...
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How to use regex with AWK for string replacement?

Suppose there is some text from a file: (bookmarks ("Chapter 1 Introduction 1" "#1" ("1.1 Problem Statement and Basic Definitions 23" "#2") ("Exercises 31" "#30") ("Notes and References 42" "#34")) ) ...
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bash extract a substring from “1.2.3-SNAPSHOT”

How can I substring a 1.2.3 from a 1.2.3-SNAPSHOT from bash? I tried echo '1.2.3-SNAPSHOT' | grep -o "^.*(?=(\-SNAPSHOT$))" but it didn't work Ideally I'd like a command to return 1.2.3 in both ...
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regex - find invalid character

Using regex='^[]0-9a-zA-Z,!^`@{}=().;/~_|[-]*$' in below script file I am checking if a given string has any invalid characters or not. str="$1" regex='^[]0-9a-zA-Z,!^`@{}=().;/~_|[-]+$' if [[ ...
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Any non-whitespace regular expression

Im trying to match a string agains a regular expression inside an if statement on bash. Code below: var='big' If [[ $var =~ ^b\S+[a-z]$ ]]; then echo $var else echo 'none' fi Match should be a ...
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1answer
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Extract URL from non-formatted text

I've found only examples on extracting substrings from formatted text like HTML files, but in my case I need to output a list of URLs for example: ... https://twitter.com/user1/status/xyza ...
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4answers
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Bulk data generation

I need to generate nearly 1 Billion records of unique integers. I tried with awk but it is not generating more than 5million records. Please help. Below is what I had tried so far - awk -v ...
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sed to match zero or more number of spaces in a string

function getVal { sedPattern='s/^.*"keyVal":"\([^"]*\)".*$/\1/' finalSedPattern=${sedPattern/keyVal/$2} echo $(sed $finalSedPattern <<< $1) } This is my Json parser written using ...
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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 ...
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In POSIX sed, does the period (dot) match a newline in a multiline pattern space?

In GNU sed it works. For example, this matches two blank lines in a multiline pattern space (created with N) /^\n$/ Is this standard?
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bash regex to find and save string from file

I'm a noob, so thanks for your assistance. Need some bash help... My file, hi.html, has many lines of text. I need to hunt down the line that starts with Hello abc123 blah blah blah and then save ...
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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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Replace only on the first matching line with sed

Using BSD sed (no GNU extensions), how can I perform an operation similar to the example provided below, but where instead of the line number, the replacement is performed on the first line in which a ...
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Parsing Log Files with sed -e. Need to count unique class names

I have a file, let's call it filename.log, in it I have something like this (2014-11-18 14:09:21,766), , xxxxxx.local, EventSystem, DEBUG FtpsFile delay secs is 5 [pool-3-thread-7] (2014-11-18 ...