Commands tagged regex sorted by votes

Commands tagged regex (60)

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Remove lines that contain a specific pattern($1) from file($2).

The -i option in sed allows in-place editing of the input file. Replace myexpression with any regular expression. /expr/d syntax means if the expression matches then delete the line. You can reverse the functionality to keep matching lines only by using: sed -i -n '/myexpression/p' /path/to/file.txt
This is sample output - yours may be different.
11

sed -i '/myexpression/d' /path/to/file.txt

jgc · 2009-11-09 11:40:45 10
Interactively build regular expressions

txt2regex can be interactive or noninteractive and generates regular expressions for a variety of dialects based on user input. In interactive mode, the regex string builds as you select menu options. The sample output here is from noninteractive mode, try running it standalone and see for yourself. It's written in bash and is available as the 'txt2regex' package at least under debian/ubuntu. Show Sample Output
This is sample output - yours may be different.
```
$ txt2regex --make date --prog vi,perl

### date LEVEL 1: mm/dd/yyyy: matches from 00/00/0000 to 99/99/9999

 RegEx vi  : [0-9]\{2\}/[0-9]\{2\}/[0-9]\{4\}
 RegEx perl: [0-9]{2}/[0-9]{2}/[0-9]{4}
```
8

txt2regex

bwoodacre · 2009-04-29 04:00:22 9
Match a URL

For the record: I didn't build this. Just shared what I found that worked. Apologies to the original author! I decided I should fix the case where http://example.com is not matched for the next time I need this. So I read rfc1035 and formalized the host name regex. If anyone finds any more holes, please comment.
This is sample output - yours may be different.
6

egrep 'https?://([[:alpha:]]([-[:alnum:]]+[[:alnum:]])*\.)+[[:alpha:]]{2,3}(:\d+)?(/([-\w/_\.]*(\?\S+)?)?)?'

putnamhill · 2009-11-28 15:41:42 33
Search for a word in less

Although less behaves more or less like vim in certain aspects, the vim regex for word boundaries (\< and \>) do not work in less. Instead, use \b to denote a word boundary. Therefore, if you want to search for, say, the word "exit", but do not want to search for exiting, exits, etc., then surround "exit" with \b. This is useful if you need to search for specific occurrences of a keyword or command. \b can also be used at just the beginning and end, if needed.
This is sample output - yours may be different.
5

\bTERM\b

kFiddle · 2009-04-11 22:05:12 6
Comment out a line in a file

This will comment out a line, specified by line number, in a given file.
This is sample output - yours may be different.
5

sed -i '19375 s/^/#/' file

BoxingOctopus · 2009-10-07 17:50:40 7
validate the syntax of a perl-compatible regular expression

Place the regular expression you want to validate between the forward slashes in the eval block. Show Sample Output
This is sample output - yours may be different.
```
$ perl -we 'my $regex = eval {qr/*/}; die "$@" if $@;'
Quantifier follows nothing in regex; marked by <-- HERE in m/* <-- HERE / at -e line 1.
```
5

perl -we 'my $regex = eval {qr/.*/}; die "$@" if $@;'

tlacuache · 2009-10-13 21:50:47 10
grep expression (perl regex) to extract all ip addresses from both ip and ifconfig commands output

It uses the following GNU grep options: "-o" which shows only the matching part of the line and "-P" which allows the use of Perl regular expressions. Show Sample Output
This is sample output - yours may be different.
```
[root@docker ~]# ip a | grep -oP '(?<=inet |addr:)(?:\d+\.){3}\d+'
127.0.0.1
10.0.2.15
172.17.0.1

[root@docker ~]# ifconfig  | grep -oP '(?<=inet |addr:)(?:\d+\.){3}\d+'
96.126.108.191
192.168.135.145
127.0.0.1
```
4

ip a | grep -oP '(?<=inet |addr:)(?:\d+\.){3}\d+'

acavagni · 2019-03-21 20:53:06 44
Use Perl like grep

If you've ever tried "grep -P" you know how terrible it is. Even the man page describes it as "highly experimental". This function will let you 'grep' pipes and files using Perl syntax for regular expressions. The first argument is the pattern, e.g. '/foo/'. The second argument is a filename (optional). Show Sample Output
This is sample output - yours may be different.
```
% printf "some\nfake\ntext\n" | prep '/^\s?[Ff]ake\s?$/'
fake
 
% printf "some\nfake\ntext\n" > file.txt

% prep '/^\s?[Ff]ake\s?$/' file.txt
fake
```
3

prep () { perl -nle 'print if '"$1"';' $2 }

dbbolton · 2011-08-13 14:29:26 7

Extract rpm package name, version and release using some fancy sed regex

This command could seem pretty pointless especially when you can get the same result more easily using the rpm builtin queryformat, like: rpm -qa --qf "%{NAME} %{VERSION} %{RELEASE}.%{ARCH}\n" | sort | column -t but nonetheless I've learned that sometimes it can be quite interesting trying to explore alternative ways to accomplish the same task (as Perl folks like to say: There's more than one way to do it!) Show Sample Output

rpm -qa | sed 's/^$.*$-$[^-]\{1,\}$-$[^-]\{1,\}$$/\1 \2 \3/' | sort | column -t

acavagni · 2019-03-14 21:11:45 35

Grab an interface's IP from ifconfig without screen clutter

Sometimes, you don't really care about all the other information that ifconfig spits at you (however useful it may otherwise be). You just want an IP. This strips out all the crap and gives you exactly what you want. Show Sample Output
This is sample output - yours may be different.
```
eth1: 192.168.100.73
```
2

ifconfig eth1 | grep inet\ addr | awk '{print $2}' | cut -d: -f2 | sed s/^/eth1:\ /g

BoxingOctopus · 2009-11-03 19:26:40 10
Open in TextMate Sidebar files (recursively) with names matching REGEX_A and not matching REGEX_B

This does the following: 1 - Search recursively for files whose names match REGEX_A 2 - From this list exclude files whose names match REGEX_B 3 - Open this as a group in textmate (in the sidebar) And now you can use Command+Shift+F to use textmate own find and replace on this particular group of files. For advanced regex in the first expression you can use -regextype posix-egrep like this: mate - `find * -type f -regextype posix-egrep -regex 'REGEX_A' | grep -v -E 'REGEX_B'` Warning: this is not ment to open files or folders with space os special characters in the filename. If anyone knows a solution to that, tell me so I can fix the line.
This is sample output - yours may be different.
1

mate - `find * -type f -regex 'REGEX_A' | grep -v -E 'REGEX_B'`

irae · 2009-08-12 22:24:08 3
VIM subst any char different from literal " + EOL with searched string + white space

---- this line ends here but must be concatenated with this one "this line ends here" and should NOT be concatenated with this one
This is sample output - yours may be different.
1

:%s/$[^\"]$$\n$/\1 /g

godzillante · 2010-09-03 11:03:49 4
recursive transform all contents of files to lowercase

In this way it doesn't have problems with filenames with spaces.
This is sample output - yours may be different.
1

find . -type f -print0 | xargs -0 perl -pi.save -e 'tr/A-Z/a-z/'

depesz · 2010-11-25 13:55:34 5
Are the two lines anagrams?

This works by reading in two lines of input, turning each into a list of one-character matches that are sorted and compared.
This is sample output - yours may be different.
1

(echo foobar; echo farboo) | perl -E 'say[sort<>=~/./g]~~[sort<>=~/./g]?"anagram":"not anagram"'

doherty · 2011-02-17 02:15:46 124
Alternative way to generate an XKCD #936 style 4 word password usig sed

This is what I came up to generate XKCD #936 style four-word password. Since first letter of every word is capitalized it looks a bit more readable to my eyes. Also strips single quotes. And yes - regex is a bit of a kludge, but that's the bes i could think of. Show Sample Output
This is sample output - yours may be different.
```
EyestrainOctogenariansCatechisingDepression
```
1

shuf -n4 /usr/share/dict/words | sed -e ':a;N;$!ba;s/\n/ /g;s/'\''//g;s/\b$.$/\u\1/g;s/ //g'

vasti · 2011-08-11 19:49:21 4
Use Perl like grep

Much better alternatives - grep-alikes using perl regexps. With more options, and nicer outputs.
This is sample output - yours may be different.
1

ack; pcregrep

depesz · 2011-08-14 18:01:36 4
Recursively search and replace old with new string, inside every instance of filename.ext

This is a slightly modified version of http://www.commandlinefu.com/commands/view/4283/recursive-search-and-replace-old-with-new-string-inside-files (which did not work due to incorrect syntax) with the added option to sed inside only files named filename.ext
This is sample output - yours may be different.
1

find . -type f -name filename.exe -exec sed -i "s/oldstring/oldstring/g" {} +;

eddieb · 2013-05-20 19:17:10 12
Find files of two different extensions and copy them to a directory
This is sample output - yours may be different.
1

find * -regextype posix-extended -regex '.*\.(ext_1|ext_2)' -exec cp {} copy_target_directory \;

shawn_abdushakur · 2014-02-06 15:58:32 9
Print the IP address and the Mac address in the same line

Print the IP address and the Mac address in the same line Show Sample Output
This is sample output - yours may be different.
```
mac:00:50:12:BD:5E:5B - adr:192.168.0.1
```
1

ifconfig | head -n 2 | tr -d '\n' | sed -n 's/.*$00:[^ ]*$.*$adr:[^ ]*$.*/mac:\1 - \2/p'

Koobiac · 2014-09-03 14:35:27 18
drop first column of output by piping to this

An advantage is that this doesn't modify remained string at all. One can change {0,1} with {0,n} to drop several columns
This is sample output - yours may be different.
1

perl -pE's/(\S+\s*){0,1}//'

pung96 · 2015-05-09 15:14:58 12
get rid of lines with non ascii characters

found here: https://stackoverflow.com/a/9035939
This is sample output - yours may be different.
1

grep -v $'[^\t\r -~]' my-file-with-non-ascii-characters

saps · 2019-03-13 14:46:02 34
extract email addresses from some file (or any other pattern)
This is sample output - yours may be different.
1

grep -Eio '([[:alnum:]_.-]{1,64}@[[:alnum:]_.-]{1,252}?\.[[:alpha:].]{2,6})'

mikhail · 2020-07-22 22:40:33 191
Test if the given argument is a valid ip address.

This command will output 1 if the given argument is a valid ip address and 0 if it is not. Show Sample Output
This is sample output - yours may be different.
```
1
```
0

perl -e '$p=qr!(?:0|1\d{0,2}|2(?:[0-4]\d?|5[0-5]?|[6-9])?|[3-9]\d?)!;print((shift=~m/^$p\.$p\.$p\.$p$/)?1:0);' 123.123.123.123

speaker · 2009-07-12 00:24:29 3
regex to match an ip

This obey that you don't match any broadcast or network addresses and stay between 1.1.1.1 - 254.254.254.254
This is sample output - yours may be different.
0

echo 254.003.032.3 | grep -P '^((25[0-4]|2[0-4]\d|[01]?[\d]?[1-9])\.){3}(25[0-4]|2[0-4]\d|[01]?[\d]?[1-9])$'

foob4r · 2009-09-17 12:59:44 7
Match a URL

From http://daringfireball.net/2009/11/liberal_regex_for_matching_urls Thought it would be useful to commandlinefuers. Show Sample Output
This is sample output - yours may be different.
```
http://foo.com/blah_blah
```
0

echo "(Something like http://foo.com/blah_blah)" | grep -oP "\b(([\w-]+://?|www[.])[^\s()<>]+(?:$[\w\d]+$|([^[:punct:]\s]|/)))"

matthewbauer · 2009-11-28 00:41:57 4
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Open a manpage in the default (graphical) web browser

An easy alias for opening a manpage, nicely HTML formatted, in your set internet browser. If you get a "command exited with status 3" error you need to install groff.

To create files with specific permission:

Dump audio from video without re-encoding.

This removes the video and subsequent file size and directly copies the audio.

Clean all .pyc files from current project. It cleans all the files recursively.

check for write/read permissions

su www-apache/ftp user and then check readable: find ~/ -type d $ -wholename '/dev/*' -o -wholename '/sys/*' -o -wholename '/proc/*' $ -prune -o -exec test -r {} \; -exec echo {} readable \; 2>/dev/null check writable: find ~/ -type d $ -wholename '/dev/*' -o -wholename '/sys/*' -o -wholename '/proc/*' $ -prune -o -exec test -w {} \; -exec echo {} writable \; 2>/dev/null

Which processes are listening on a specific port (e.g. port 80)

swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

tar exclude files or directories

If you want to exclude only one file or directory you should use as --exclude=file_or_directory

Terrorist threat level text

Convert seconds to [DD:][HH:]MM:SS

Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Count items in JSON array

Pipe any JSON to jq, then count with the appropiate expression and use the | length on the array

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Commands tagged regex (60)

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