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

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Add text between multiple lines with sed if previous line does not match pattern

I'm struggling to add <dl> tags around a definition list with sed, and perhaps there is an easier way to do it (I'd love to know). I would like to search a file for any lines that contain a <...
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“egrep: empty (sub)expression” when attempting to filter out words from a list

I'm trying to follow this question/answer from Server Fault: In tail -f, how do I filter out stuff that has certain keywords? The following is producing egrep: empty (sub)expression: # Respect user'...
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217 views

pkill with regex

I have few java processes running like below, java -jar /my/path/to/app/myapp.jar java -jar /my/path/to/app/prodapp.jar java -jar /my/path/to/app/testapp.jar java -jar /my/path/to/app/myapp_v.01....
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Regex quantifiers are not working well with locate

This output is rather self-explanatory: XXXXX@debianvirtualbox:~$ locate -r "^/var/lib/tomcat[0-9]/.*" -l 10 /var/lib/tomcat8/conf /var/lib/tomcat8/lib /var/lib/tomcat8/logs /var/lib/tomcat8/webapps /...
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Including or in grep pattern

I want to grep a word wrap in single quote or double quote eg. "myWord" 'myWord' I am using grep -rn "\"\|\'myWord\'\|\"" this should allow "myWord" , 'myWord" , "myWord' and 'myWord' , but ...
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Match regular expression between delimiters

I have a file with several different lines. I'm looking for lines that contain(more or less) pattern like this: \[.*<.*>.*\] In other words, I want the lines that have <something> ...
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Bash script with “execute” command and strange regexp

So I was looking through Paul Irish's dotfiles and found reference to this bash script: #!/bin/bash cd "$(dirname "$BASH_SOURCE")" \ && source 'utils.sh' declare -a FILES_TO_SYMLINK=( ...
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searching for the c++ in a string (regular expression)

I want to find if a string contains c++ in it (regular expression). what pattern should I use in grep function in R? This is my error: Error in grep(pattern = "c++", x = df[trow, "modeling"]) : ...
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How to detect end of line with sed

I'm looking for a way to only execute replacement when the last character is a newline, using sed. For instance: lettersAtEndOfLine is replaced, but this is not: lettersWithCharacterAfter& ...
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Delete text from a file using regular expressions

I have lots of text in a file. I want to delete all text that are between symbols === and <!!!>. E.g. Text ===some comments<!!!> lala ===aaa<!!!>" should be Text lala after running ...
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Problem with sed substition in multi-word regex

Take this simple example: echo "20150310 21:12:01.846338::: <?xml version="1.0"?><Haystack><Event " \ | sed 's/^\(.\{24\}\)::: \(<?xml.*><Haystack\|Foo\)>\(.*\)/\2 ts=\"\1\"...
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Search and replace two words with ex command

I want to search and replace 2 words with 2 other words with one g/.../s/.../.../g command. For example to replace word 'car' with 'truck' and 'cat' with 'dog' with one ex command in Vim.
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Erasing in stdin all instances of regexes defined in a file

I am after something like a combination of sed 's/pattern//g' and grep -f patternfile.txt. Basically I would like the input stream to be stripped of all instances of the regex patterns defined in ...
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49 views

awk regex matches wrong?

Playing around with awk I noticed this behavior: [root@ror6ax3 ~]# grep open * | awk '$2 ~ /opens*/ {print $0}' install.log:Installing openldap-2.4.23-32.el6_4.1.x86_64 install.log:Installing openssl-...
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grep for text that may or may not be present

Lets say I have a file batman; robin; superman; password = ""; wonderwoman green lantern if I want to check if there is a password present, i.e there is something entered in the "" . here is an ...
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To bold one line with Perl regex

I have 1. Lorem He he he % not sure spelling 2. Lorem ipsun I want to have \textbf{1. Lorem} He he he % not sure spelling \textbf{2. Lorem} ipsun My pseudocode attempt perl -000pe 's/\n\n\d....
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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 ...
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Need to remove lines till a pattern is matched

My C code needs to decode some application data that were received over a socket by another application. I used the Wireshark to export the packets(many) into a C array. But the array carries all ...
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588 views

How does “$” work in “apt-cache search something$”

I understand that $ apt-cache search package_name will search for matches in names and descriptions. But how does this work? $ apt-cache search package_name$ For example, $ apt-cache search ...
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using grep --perl-regexp

this is a sample output of ls $ ls -lAF -rw------- 1 martin martin 168 Jan 25 23:26 aaa -rw------- 1 martin martin 168 Jan 25 23:26 bbb -rw------- 1 martin martin 168 Jan 25 23:26 ccc I would ...
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How to get numbers by using regular expression, but only last one

In this example I can get 00. expr match "00 foo 99.jpg" '[^0-9]*\([0-9]\+\).*$' I want to know how to get last number from string, in this case 99 by using regular expression. The string may ...
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Backreferencing with sed

I have a database containing a list of unsigned longs representing a bunch of memory addresses followed by an offset within two brackets (e.g. Mem[offset], 0x2322AD4[3]), and some other data. What I ...
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What are the commands that you can use in the beginning of a sed command?

I initially learned to do sed search and replace like so: sed -e 's/<stuff>/<replacement>/' However I recently learned that these will do something different based on what command ...
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Replace text between brackets

I'm using awk '{ gsub(/BAR|WIBBLE/, "FOO"); print }' to replace text in data like: SOMETHING [BAR, WIBBLE] SOMETHING [BAR] This gives the desired result of: SOMETHING [FOO, FOO] SOMETHING [FOO] ...
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Replacing XML entity values with positive lookaround

I'm trying to do some pretty simple sedding of a file: sed 's:(?<=<Type>)default(?=</Type>):super:' < myfile.xml The concept's pretty simple, using positive lookaround, find the ...
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Regex : all greek letters with 5 unique letters (meaning that each letter only appears once)

Another one I can't seem to solve : all greek letters with 5 unique letters (meaning that each letter only appears once). my solution : egrep '(.)([^/1])([^/1/2])([^/1/2/3])([^/1/2/3/4])' greek.txt ...
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substitute at beginning of line

I want to search a pattern and insert a character at the beginning of a line using regsub in TcL. I have to use TcL only Input file mna1 x a1 vss vbn nch_svt_mac nfin=nfin_n1 l=ln1 mna2 x a2 vss vbn ...
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Command line tool for easy multiline regex search and replace

I use PCRE regular expressions for search and replace very often when working with a text editor and I was left quite unhappy after I found out that in powerful Unix command line tools like perl, awk ...
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egrep doesn't work as expected on SunOS system

Here is what I want to achieve on SunOS: Only pattern like [text_text=text], [text=text], [text] or text are valid patterns, where by text I mean anything in 0-9,a-z,A-Z, space, newline, tab, enter. ...
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Which of the following use of anchor is correct in regex using grep?

Both of the below commands gives the same output, however which one is the correct method to use it? grep ^'\<that\>' file.txt Searches for the line which has that as the first word grep '^\&...
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string substitution using sed

I have this string for example : asddsa "ll" sadd " fsgsg" "sdafaf" "lkkx" "fsgfgsg" I want to substitute all characters inside " " with a character x. Expected output in this case should be: ...
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Using sed to substitute a string containing variable integers

I have a text file and want to use sed to replace the following string (including the "s): " rel="lightbox[1846]" title=" with # The numbers between [ and ] are variable and change. I want to ...
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37 views

List lines that consist of a single non-vowel character

I need help with listing lines that consist of a single non-vowel character. I got this: ls | grep -nv '[aeiouy]' file But this doesn't give me a single character. How do I get just a single ...
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multi line awk regular expression [duplicate]

Consider text.txt with this content: blablabla &&&key word&&& I want all these text and numbers 123 and chars !"£$%& as output &&&key word&&& ...
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Egrep back referencing not working

I have trying top back reference the first captured group in the below command: $ ls -lR | egrep 'd(rw(x|s)|rw-|r-(x|s)|-w(x|s)|r--|-w-|--(x|s))(rw(x|s)|rw-|r-(x|s)|-w(x|s)|r--|-w-|--(x|s))---' drwxr-...
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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 sed....
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Use of \$ at end of variable name passed to grep

I was going through one of the shell scripts and found a line: ls $dir | grep -c "$NAME.${var}\$" I understand that $ would expand the variables NAME and var, but is it required to put \$ at the ...
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How do I keep a part of the pattern matched and use it to replace on BSD sed?

I have found a soultion for GNU sed, and I also found something like \1, but the Terminal tells me it's "not defined in RE". But what I want to do is this: If I have a string that looks like this ...
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60 views

check if row contains characters

I have file that looks like This row contains characters this row to *-=?§/ this is the lat row of the file how can i only print only rows that contains some characters aka all but ...
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usage of apostrofe in grep rexExp

I have recently started learning regExp and found nice example of it in shell using grep to extract only anchor tags url e.g <a href="unix.stackexchange.com"></a> grep - 'href="[^"]*"' *....
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Is it possible to make sed doing some logic in the replacement part (regex group)

I have few sed command: to extract relevant information My file sample.log (format is ncsa.log) looks like: 2012_04_01_filename.log:29874:192.168.1.12 - - [16/Aug/2012:12:54:21 +0000] "GET /cxf/...
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REGEX and GREP — Search string including optional and static words

I am trying to formulate a regex expression for use with grep such that I find a static word present at the beginning of each line, followed by only one word from a list of options. That is, I ...
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Find works fine in command line, but won't work in script

I am trying to write a script on a Debian Jessie host. I am having an issue with trying to run the following command (with a twist) in a script: find ~/* -path ~/FileSniper* \ -prune -o \ -type f \( ...
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how to swap text inside files [duplicate]

Inside my file I need to swap places of all instances of : grep 'search string' and sed '/string of text/,/string of text/{//!d}' In VI I have tried a regex with no luck - it says something ...
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Remove word after match

Consider the following line of text (taken from a MySQL insert): "description" varchar(255) COLLATE utf8_unicode_ci NOT NULL DEFAULT '', I want to return "description" varchar(255) NOT NULL ...
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grep also returning non matching lines

I'm trying to grep the output of strings and only find lines that start with a certain number of = chars. I tried strings data.txt | grep ^=* Sample output: 1~{, WX2 };K,< ========== ...
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Grep and ignoring leading whitespace

I've been working on a bash script to search for names of defines, and then grab the hex values for them and put them in the list. Once I have the list of names I'll attempt to search for "#define [...
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103 views

Regex for surrounding every word that contains & with $…$

I am thinking what is a robust approach for this. I try to match unsuccessfully by: [A-Za-z]*&[A-Za-z]* Which returns: so the mistake in \\&\hskip environment. How can you match ...
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Pattern matching inside awk

I intend to modify the output of ls -la to display the output of file command. The below command works well for the purpose find /opt -type f | xargs ls -let | awk 'BEGIN { OFS="\t" } { sprintf("file ...
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What is the email matching regex in basic regex for grep?

I created a text file and put some email addresses in it. Then I used grep to find them. Indeed it worked: # pattern="^[a-zA-Z0-9]+@[a-zA-Z0-9]+\.[a-z]{2,}" # grep -E $pattern regexfile but only as ...