Commands using perl (369)

  • Pick a random line from a file

    This is from perldoc -q random.*line, which says: This has a significant advantage in space over reading the whole file in. You can find a proof of this method in The Art of Computer Programming, Volume 2, Section 3.4.2, by Donald E. Knuth. Who am I to argue with Don Knuth?


    1
    perl -e 'rand($.) < 1 && ($line = $_) while <>;'
    unixmonkey20842 · 2011-04-25 21:28:26 3
  • Perl Command Line Interpreter

    Can also just use the debug mode like this. Show Sample Output


    1
    perl -dwe 1
    bashrc · 2011-05-05 20:28:03 6
  • Mark packages installed with build-dep for autoremove (on Debian/Ubuntu)

    Replace PACKAGE with desired package name. Found here: http://mikebeach.org/2011/04/undo-apt-get-build-dep/


    1
    sudo aptitude markauto $(apt-cache showsrc PACKAGE | grep Build-Depends | perl -p -e 's/(?:[\[(].+?[\])]|Build-Depends:|,|\|)//g')
    Lexton · 2011-05-08 14:18:52 6
  • Delete empty directories

    Recursively delete empty directories. Use with care.


    1
    perl -MFile::Find -e"finddepth(sub{rmdir},'.')"
    igorfu · 2011-05-23 08:45:34 7
  • Scan for [samba|lanman] NetBIOS names and ip addresses in LAN by ARP.


    1
    arp-scan -I eth0 -l | perl -ne '/((\d{1,3}\.){3}\d{1,3})/ and $ip=$1 and $_=`nmblookup -A $ip` and /([[:alnum:]-]+)\s+<00>[^<]+<ACTIVE>/m and printf "%15s %s\n",$ip,$1'
    bandie91 · 2011-07-08 07:41:41 3
  • Syntax Highlight your Perl code


    1
    perl -mText::Highlight -E 'say Text::Highlight->new(ansi => 1)->highlight(Perl => do { local (@ARGV,$/) = shift; <> }) ' path/to/perl-file.pl
    dbr · 2011-07-12 04:55:12 5
  • change microdvd subtitles framerate

    this command example converts to 25 fps subtitles that were originally created for 24 fps movie


    1
    cat subtitles.txt | perl -pe 's/} /}/g; s/{(\d+)}/=1=/; $f1=(24/25*$1); s/{(\d+)}/=2=/; $f2=(24/25*$1); $f1=~s/\..*//; $f2=~s/\..*//; s/=1=/{$f1}/; s/=2=/{$f2}/; ' > subtitles_newfps.txt
    ciekawy · 2011-07-30 15:34:43 18
  • Lookup errno defintions

    Calls the POSIX strerror() function to look up the meaning of integer ERRNOs set by some functions.


    1
    perl -MPOSIX -e 'print strerror($ARGV[0])."\n";' ERRNO
    sethjust · 2011-09-21 18:16:19 5
  • Multiline Search/Replace with Perl

    from http://stackoverflow.com/questions/1030787/multiline-search-replace-with-perl added greedy trick in wildcard match (.*?) from http://www.troubleshooters.com/codecorn/littperl/perlreg.htm#Greedy Show Sample Output


    1
    perl -i -pe 'BEGIN{undef $/;} s/START.*?STOP/replace_string/smg' file_to_change
    hute37 · 2011-10-05 11:22:36 10
  • one-line log format for svn

    the output of svn log is annoying to grep, since it spreads the useful info over multiple lines. This compacts the output down to one line so eg you can grep for a comment and see the rev, date & committer straight away. Updated: MUCH shorter, easier to remember. Now it just replaces newlines with spaces, except on '---' lines. Show Sample Output


    1
    svn log | perl -l40pe 's/^-+/\n/'
    bazzargh · 2011-10-14 16:02:22 6
  • wc in perl


    1
    perl -ane 'END{printf(" %d %d %d\n", $x, $y, $z)} $x+=1; $y+=@F; $z+=length' file.txt
    kev · 2011-10-24 06:14:02 10
  • Create new user with home dir and given password

    The crypt function takes a password, key, as a string, and a salt character array which is described below, and returns a printable ASCII string which starts with another salt. It is believed that, given the output of the function, the best way to find a key that will produce that output is to guess values of key until the original value of key is found. from http://en.wikipedia.org/wiki/Crypt_(Unix)


    1
    useradd -m -p $(perl -e'print crypt("passwordscelta", "stigghiola")') user
    0disse0 · 2012-02-06 19:53:01 7
  • One line Perl Script to determine the largest file sizes on a Linux Server

    This one line Perl script will display the smallest to the largest files sizes in all directories on a server. Show Sample Output


    1
    du -k | sort -n | perl -ne 'if ( /^(\d+)\s+(.*$)/){$l=log($1+.1);$m=int($l/log(1024)); printf ("%6.1f\t%s\t%25s %s\n",($1/(2**(10*$m))),(("K","M","G","T","P")[$m]),"*"x (1.5*$l),$2);}' | more
    Q_Element · 2012-02-07 15:49:19 10
  • Tracklist reaplace backspace to '-'

    Requires perl 5.14 or greater


    1
    perl -e 'rename $_, s/ /-/gr for <*.mp3>'
    ironcamel · 2012-02-21 17:07:18 4
  • Perl oneliner to print access rights in octal format

    This prints file access rights in octal - useful when "stat" is unavailable. Show Sample Output


    1
    perl -e 'printf "%04o\n", (stat shift)[2] & 0777;' file
    zlemini · 2012-03-22 15:05:04 9
  • multiline data block parse and CSV data extraction with perl

    extract data in multiline blocks of data with perl pattern matching loop Show Sample Output


    1
    cat z.log | perl -ne 'BEGIN{ print "DATE;RATE\n"; } /\[(\d.*)\]/ && print $1; /CURRENT RATE: +(\S+) msg.*/ && print ";" .$1 . "\n"; '
    hute37 · 2012-04-03 13:52:20 3
  • Perl One Liner to Generate a Random IP Address


    1
    perl -e 'printf "00:16:3E:%02X:%02X:%02X\n", rand 0xFF, rand 0xFF, rand 0xFF'
    Gular · 2012-07-02 09:59:43 5
  • Encode file path to URL

    Really helpfull when play with files having spaces an other bad name. Easy to store and access names and path in just a field while saving it in a file. This format (URL) is directly supported by nautilus and firefox (and other browsers) Show Sample Output


    1
    convert_path2uri () { echo -n 'file://'; echo -n "$1" | perl -pe 's/([^a-zA-Z0-9_\/.])/sprintf("%%%.2x", ord($1))/eg' ;} #convert2uri '/tmp/a b' ### convert file path to URI
    totti · 2013-07-01 08:54:45 7
  • Update a namecheap @ A record to point to your current internet-facing IP address

    Sets the @ A record for your domain hosted by namecheap to your current internet-facing IP address, logs success or failure with syslog, and logs the data returned to /root/dnsupdate. Change the XXX's as appropriate. More info at: http://www.namecheap.com/support/knowledgebase/article.aspx/29/ Show Sample Output


    1
    logger -tdnsupdate $(curl -s 'https://dynamicdns.park-your-domain.com/update?host=@&domain=xxx&password=xxx'|tee -a /root/dnsupdate|perl -pe'/Count>(\d+)<\/Err/;$_=$1eq"0"?"Update Sucessful":"Update failed"'&&date>>/root/dnsupdate)
    MagisterQuis · 2013-08-11 16:27:39 7
  • send raw data (hex written)using UDP to an IP and port

    Use it to send raw data to a networked device. Used to interact with relay controller board whose documentation is lost, so use wireshark to sniff the sent data and replayed using the command.


    1
    echo -n 023135 | perl -pe 's/([0-9a-f]{2})/chr hex $1/gie' | nc -4u -q1 -p5001 192.168.0.100 2000
    sucotronic · 2013-09-18 14:31:47 7
  • Convert control codes to visible Unicode Control Pictures

    Converts control codes and spaces (ASCII code ≤ 32) to visible Unicode Control Pictures, U+2400 ? U+2420. Skips \n characters, which is probably a good thing. Show Sample Output


    1
    /bin/echo -e '\002Hello, Folks\t!\r' | perl -pwle 'use v5.14; s/([\N{U+0000}-\N{U+0020}])/chr(9216+ord($1))/ge;'
    scruss · 2014-06-30 01:45:40 11
  • 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


    1
    perl -pE's/(\S+\s*){0,1}//'
    pung96 · 2015-05-09 15:14:58 12
  • Get all shellcode on binary file from objdump

    Better than the others, and actually works unlike some of them. Show Sample Output


    1
    objdump -d $1 | grep -Po '\s\K[a-f0-9]{2}(?=\s)' | sed 's/^/\\x/g' | perl -pe 's/\r?\n//' | sed 's/$/\n/'
    Daytona · 2015-05-23 01:21:58 10
  • Get the SAN (subjectAltName) of a site's certificate.

    Based on http://stackoverflow.com/questions/13127352/checking-alternative-names-for-a-san-ssl-cert Replace "facebook.com" with the desired hostname. Show Sample Output


    1
    echo "quit" | openssl s_client -connect facebook.com:443 | openssl x509 -noout -text | grep "DNS:" | perl -pe "s/(, )?DNS:/\n/g"
    lgarron · 2015-08-13 22:50:45 9
  • Find all file extension in current dir.


    1
    find . -type f | perl -ne 'print $1 if m/\.([^.\/]+)$/' | sort -u
    wuseman1 · 2018-11-11 01:09:42 530
  • ‹ First  < 5 6 7 8 9 >  Last ›

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Check These Out

Get MX records for a domain
command is shorter, output unnecessary longer

Save a file you edited in vim without the needed permissions (no echo)
Write a file you edited in Vim but that you do not have the permissions to write to (unless you use sudo.) Same as #1204 but without the echo to stdout that I find annoying.

Extract audio from Mythtv recording to Rockbox iPod using ffmpeg
There are some pretty good live performances on late night TV. With Mythtv I record David Letterman, Jimmy Fallon, and Conan nightly all in HD from over the air broadcasts. If I find a live performance I like I copy it to my Rockboxed iPod using this command. The Rockbox firmware knows how to downmix 5.1 audio. The command above extracts the audio from the video starting at 58 minutes and 15 seconds. It ends at the end of the file since this was the last performance of the recording. The command creates an ac3 file. I copy the ac3 file to my Rockbox iPod and rock on.

Job Control
background and disown, but with a proper one-line syntax

find and reduce 8x parallel the size of PNG images without loosing quality via optipng

list files recursively by size

Extract audio from a video
With the -vn switch we make our intentions clear and ask FFmpeg not to bother itself with the video. Next we specify the audio codec copy, which tells FFmpeg to use the same codec to encode the audio, which it uses to decode it. To keep things simple, we'll just keep the sampling and bitrate values the same.

Replace php short open tags
Tired of front end developers using short open tags in your views? This will replace all instances of

list files recursively by size

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: