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

learn more… | top users | synonyms (1)

3
votes
1answer
52 views

Accept only y or yes with a one-line regular expression

I want to check if an input is y or yes (inputs in lowercase) and reject everything else What I have now is ^y[e]{'0,1'}[s]['0,1']$ But this accepts y, ye, ys, yes. I don't want ye and ys to be ...
2
votes
3answers
90 views

bash: regular expressions in if expression

In my script on my ubuntu machine I declare a string like this: DEBUG_PACKAGE_LIST=$(apt-cache search dbg | awk '{ print $1 }' | grep -e "-dbg") For you to help you understand my problem here is ...
2
votes
4answers
633 views

Matching string with a fixed number of characters using grep

I am trying to find all 6 letter words using grep. I currently have this: grep "^.\{6\}$" myfile.txt However, I am finding that I am also getting results such as: étuis, étude. I suspect it has ...
0
votes
2answers
44 views

add bracket across numbers at only end of each line

I have a file having lines as: ram_reg_10/raja_reg_9/raghu_reg_8 abc_reg_4/bcd_reg_5 cad/pqr_reg_91 I want to convert string "_reg_number" into [number] at only last of every line in vi ...
5
votes
3answers
617 views

How to remove dot and space from beginning of filenames

I'm trying to change jpg files named with a dot and a space at the beginning and with a missing dot before the end (like this . Startjpg to Start.jpg The dot makes the files hidden from sed and ls ...
2
votes
3answers
629 views

Reverse match in sed, replace opposite of what was found

Say I have this output from my syslog, precalculated src_hash => 20 bytes @ 0x7f811c001e20 A6 2D E5 CD 2A BA F0 42 56 66 19 D4 61 1A E3 A0 .-..*..BVf..a... C7 5E 5F 77 ...
4
votes
6answers
231 views

Finding the number of time a particular number in a file where range also specified

I have a file with numbers separated by ,(comma). In between it also contains a number range like 300-400. Say for example I have a text file, namely testme.txt which looks like, ...
4
votes
2answers
95 views

sed regex issue

I'm trying to replace a string in a file: $RELEASE = '1234'; The whitespace between RELEASE and the = symbol could be either spaces OR tabs. The quotes around the version number could be either ...
4
votes
3answers
775 views

Regex alternation/or operator (foo|bar) in GNU or BSD Sed

I cannot seem to make it work. GNU sed documentation says to escape the pipe, but that doesn't work, nor does using a straight pipe without the escape. Adding parens makes no difference. $ echo ...
1
vote
4answers
1k views

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 ...
2
votes
1answer
457 views

Removing non-printable characters using POSIX sed

Files created with roff and other "old-school" tools (for example man pages on many Unix systems) generate bold and underlined text in minimalistic terminals using tricks involving non-printable ASCII ...
5
votes
1answer
782 views

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 ...
4
votes
3answers
280 views

Search and replace strings that are not substrings of other strings

I have a list of replacements like so: search_and -> replace big_boy -> bb little_boy -> lb good_dog -> gd ... I need to make replacements for the above, but at the same time avoid ...
2
votes
3answers
292 views

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 ...
0
votes
3answers
404 views

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 ...
1
vote
1answer
34 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 ...
3
votes
1answer
87 views

How do back-references match in sed?

I found a one-line sed command on this site which removes duplicate entries in $PATH. There is one concept that I can't get my mind around. It uses saved matches in the match section to detect the ...
1
vote
1answer
109 views

Why does the same sed regex (after grep) fail when run in a bash script vs bash command line?

Here's the script. It is successful when I run it from the BASH prompt, but not in the script. Any ideas? When I say "fails," I mean the sed regex doesn't match anything, so there is no replaced ...
0
votes
0answers
14 views

Using regex in locate [duplicate]

I would like to search for both words pdf and hack in all filenames and their paths. The order of the two words doesn't matter. I use the command locate with a regex pattern: locate --regex ...
6
votes
5answers
246 views

Strategy to extract movies's name from this ununiform dataset?

I am working on a movie database problem to improve regular expressions, this is the problem I'm running into. My dataset looks like this: Movie Name (variable space and tabs) year Movie1(can ...
4
votes
3answers
649 views

Which regular expression methods to validate input could be used in shell scripting?

#!/bin/sh re="\/$" if [ $1 =~ $re ]; then echo "${ATTENTION_PREFIX}$1 DIRECTORY MAY NOT CONTAIN A \"/\" OR LITERAL SLASH!${ATTENTION_POSTFIX}" exit 1 fi Executing sudo file.sh ...
2
votes
1answer
56 views

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 ...
7
votes
3answers
892 views

Print all lines not containing punctuation

I want a regex pattern which can print all lines not containing punctuation : Input : .I am line 1 I am ! line 2 I am line (3) I am line 4 Output: ( should be) I am line 4 What I've tried so ...
2
votes
3answers
77 views

A challenge for sed convert code from Mathematica to Matlab

I have the following output from Mathematica to C code: $ cat file.txt Complex(1.3, 2.7)*Power(kappa, 2.0) + Complex(0.3, 2.0)*Power(kappa,5.0)*log(alpha) The file is extremely long (many tens of ...
2
votes
1answer
206 views

sed regexp HEX char

i have this string: echo -e "a12\x8fb12\x9f"|xxd 0000000: 6131 328f 6231 329f 0a a12.b12.. i want delete this sequence string 12\x9f and 12\x8f with sed. i can do it with this ...
2
votes
2answers
86 views

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 ...
1
vote
4answers
346 views

Enclose multiple lines in quote Vim

I have blocks of the following form: String that is not supposed to be enclosed in quotes String that is supposed to be enclosed in quotes String that is not supposed to be enclosed in ...
2
votes
1answer
72 views

How to match a particular form of optional sequence from a manual synopsis, including variations?

In this Q&A there is a reference to the manpages synopses being based "loosely" on the Extended Backus–Naur Form of metasyntax notation. It's interesting and serves as background. That being said, ...
1
vote
5answers
66 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
votes
2answers
99 views

How to get `expr match` to extract colon-delimited key-value pair?

Given: myvar="present-value: 1", I'd expect expr match "$myvar" '\([0-9]\)' to output 1. However, instead it outputs blank and exits with a non-zero status code indicating no match. How can I get it ...
3
votes
1answer
779 views

How to perform a multiline grep across multiple files?

I'm trying to grab this pattern wherever it occurs in multiple log files (Note:these patterns can vary greatly in size, i.e. the amount of Blahs): Found an txt File Blah Blah 10019874 ...
0
votes
3answers
105 views

Finding and replacing text inside awk block

I want to find and replace a value inside awk block. Here is a sample input file to my script P1 10,9:11/18013013582 ,10:1 ,167:0 ,487:5/E.164 11,9:15/310410532169026 ,10:60 ,167:0 ,487:4/IMSI ...
1
vote
2answers
479 views

Aix grep wildcard not working

I have a file called message that has the line CSC/UT/USA/WBIMB/SAP/orders05:orders05/ORDERS05/NONE/ORDRSP/758 I am doing a grep (Platform is AIX 6.1) grep ...
3
votes
3answers
142 views

History of Bash globbing

Is there a historical reason why Bash "globbing" and regular expressions are not identical? For example, I believe that in Bash [1-2]* matches anything that starts with a 1 or a 2 followed by anything ...
1
vote
3answers
54 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 ...
2
votes
3answers
115 views

Apply item replacement inside enumerate in Perl regex?

Data 7. Masi is the same as \begin{enumerate} A B ABC ha lorem \end{enumerate} 1. ABC is \begin{enumerate} P B Lorem maam \end{enumerate} which I want to be 7. Masi is the same as ...
2
votes
3answers
316 views

Find a pattern with no repeated numbers in egrep

I need help finding a regular expression to match all digit sequences which has no repeated digit. Example: 198345 -> matched. 198315 -> not matched (1 repeated twice ) How can I achieve this in ...
2
votes
1answer
163 views

csplit not obeying backslash r \r as carriage return

I have a file with \r\n line endings (CRLF carriage return line feed). This command works: $ csplit --silent --prefix=email-emailbad.txt- \ --digits=3 emailbad.txt '/^\.^M/'+1 '{*}' This ...
0
votes
2answers
230 views

How to match date in Perl — assuming UNIX regex is the same as Perl's

I want to match dates of the form Monday May 26 My attempt to do this is the following: /(.*day Jan.*|Feb.*|Mar.*|Apr.*|May|Jun.*|Jul.*|Aug.*|Sep.*|Oct.*|Nov.*|Dec.* [1-31])/ The regex form in ...
3
votes
3answers
334 views

How can I get the first column of a 300GB txt file?

let me first explain my problem in detail. It's actually pretty simple. I have a huge .txt file, 300GB to be more preciese, and I would like to put all the distinct strings from the first column, that ...
1
vote
1answer
719 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 ...
2
votes
6answers
3k views

Regex that would grep numbers after specific string

So I have a line: ID: 54376 Can you help me make a regex that would only return numbers without "ID:"? NOTE: This string is in a file.
0
votes
4answers
88 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
2answers
389 views

Regular expression find 3 or 4 numbers

So, I have 50+ words and I have to match the numbers in them. These numbers can be 3 or 4 digit numbers. I think I tried every way there is, but nothing seems to work (I need to remember the number as ...
3
votes
5answers
136 views

How to “grep” a string of a returned result

How to grep the number 50.0 from the string temp=50.0'C In JavaScript I can use the expression /temp=(.*?)'C/ to get it. But I cant get it running in grep.
0
votes
1answer
185 views

Search for pattern across multiple files and replace a sub-part in all occurences

I am helping a friend with her thesis written in LaTeX and I need a quick solution for a "search and replace". Using a terminal in Linux, how can I find the following pattern: \caption{*\cite{*}} ...
1
vote
5answers
129 views

Extract one occurrence of a pattern from file

I have large file containing logs similar to one shown below. I would like to find all transactions(TR#) that were affected with the error. I need to extract one occurrence of each TR# ID. How could ...
-1
votes
2answers
95 views

Regular expressions in a shell [duplicate]

I have two questions about using regular expressions inside a shell. 1. Use of * According to wikipedia page on regular expressions: *: The asterisk indicates there is zero or more of the ...
0
votes
1answer
216 views

bash using grep and sed

This is for our weekly prac, no marking or grade (we don't even get the answers!) I'd really appreciate it if anyone has the time to help explain this exercise to me, as I'm trying to get this work ...
1
vote
2answers
116 views

Lazy regex using Bash

I'm trying to match just the text contained within the HTML tags using Bash's built-in regex function: string='<span class="circle"> </span>foo</span></span>' regex='<span ...