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

learn more… | top users | synonyms (1)

1
vote
5answers
93 views

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 ...
1
vote
3answers
261 views

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....
1
vote
4answers
180 views

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 ...
1
vote
1answer
102 views

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 ...
1
vote
2answers
552 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 ...
1
vote
1answer
420 views

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 ...
1
vote
3answers
2k views

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 ...
1
vote
2answers
357 views

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 ...
1
vote
1answer
145 views

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 ...
1
vote
4answers
2k views

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] ...
1
vote
3answers
4k views

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 ...
1
vote
2answers
515 views

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 ...
1
vote
1answer
32 views

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 ...
1
vote
1answer
50 views

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. ...
1
vote
2answers
41 views

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 '^\&...
1
vote
1answer
29 views

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: ...
1
vote
2answers
43 views

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 ...
1
vote
1answer
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 ...
1
vote
1answer
60 views

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&&& ...
1
vote
2answers
37 views

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-...
1
vote
2answers
37 views

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....
1
vote
2answers
60 views

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 ...
1
vote
1answer
36 views

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 ...
1
vote
1answer
56 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 ...
1
vote
1answer
47 views

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="[^"]*"' *....
1
vote
3answers
67 views

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/...
1
vote
1answer
56 views

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 ...
1
vote
2answers
111 views

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 \( ...
1
vote
2answers
89 views

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 ...
1
vote
1answer
54 views

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 ...
1
vote
1answer
59 views

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,< ========== ...
1
vote
2answers
311 views

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 [...
1
vote
2answers
100 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 ...
1
vote
1answer
145 views

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 ...
1
vote
1answer
807 views

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 ...
1
vote
2answers
5k views

Pages don't get blocked with Squid over HTTPS

I have set up Squid to block pages on my own system (i.e not on a network), and I'm trying to get SSL to work with page blocking. To this end, I've set up ssl-bump and installed the certificate to my ...
1
vote
2answers
173 views

Remove a line if regex exists only in 1st column of each line in a csv file

I have the following comma-delimited data (spaces used for visual clarity): 1 2014 23 2352 19.24 7.18 1 2014 23 2353 19.78 4.65 24 2014 23 2354 20.26 25.34 1 2014 23 2355 26.65 42.76 1 2014 23 ...
1
vote
1answer
220 views

How to find strings using regular expressions in grep

So I have a file list with list of the people in a company. Each line contains Position(a short string), years, name(first and last), salary and nationality(three capital letters). They are divided ...
1
vote
1answer
65 views

Search and remove with regular expression

How do you use regular expression in bash to search any given string and remove occurrence of particular word? This is the expression I've come up with ^([A-Za-z-]+)(-).*(el6.*)$ What I would like ...
1
vote
1answer
186 views

perl rename: Prepending something to a set of file names across subdirectories

Although perl's rename tool has become an invaluable companion for my daily work, there are still some quirks that make work more difficult - especially when files are not in current work directory. ...
1
vote
1answer
181 views

How to nest global matches with sed?

If I do: sed 's/match/replace/g' I know that sed will substitute replace for every occurrence of match on a line. But what if...? echo "match <please dont match this?>" | sed 's/match/...
1
vote
1answer
2k views

Interpret an interpolated variable as a literal string in Perl regex

I am using perl to colorize a matched string MATCH=aaa printf "aaa\n/dev/aaa\nccc\n" | perl -pe "s/($MATCH)/\e[1;31m\1\e[0m/g" This works well until I try to match a string containing special ...
1
vote
1answer
687 views

awk date identification from input file

I currently have daily files that come in via FTP with incorrect dates in the first column of the file. I have figured out how to deduct one day to derive the correct date and print this to a new file....
1
vote
2answers
100 views

How can I append multiple extensions to a string with sed?

I want to create a script that will let me download images from entire subreddits at once, but I'm currently stuck on just getting the links right (one problem at a time! ^^). Anyway, since I can't ...
1
vote
2answers
1k views

Why is my grep + regex not working?

I recently decided that enough was enough -- I was going to learn to use grep fluently. It's been all of three hours and I'm already stumped by this toy problem. I'm currently syncing a RAID5 array, ...
1
vote
2answers
273 views

Ensure /etc/export contains rule using bash

What's a working example of modifying /etc/export using bash? Example: I want to ensure the following rule is present and valid: /export/home 2400:123::/32(rw,no_root_squash) And it should: Add ...
1
vote
3answers
118 views

a string representation using regex (modified)

I would like to use regular expression to represent a pattern with the following type of characteristics 1) It includes a continuous sequence of digit values. The length of this sequence it at least ...
1
vote
2answers
166 views

Remove 2 and 3 newlines in a text file but not 1

I'm developing on a max osx 10.8 and have no preferences to which tool to use probably sed but it doesn't matter. Update after comment: The input file uses windows new lines if that's complicates ...
1
vote
1answer
272 views

Comment the if statement and the matching endif keyword

In vim, I can find the matching if statement and prepend the appropriate comment symbol. (e.g. %s/.alarm./#\0/g), but then I am left with dangling endifs that I have to find manually. I could simplify ...
1
vote
1answer
62 views

cclive: what kind of regexes are allowed?

Is there a place where I can look, what kind of regexes I can use with the --tr option from cclive?