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

Easily search running processes (alias).

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" }

postgresql SQL to show count of ALL tables (relations) including relation-size
Postgresql specific SQL - to show count of ALL tables including relation-size (pg_relation_size = used space on filesystem) - might need a VACUUM ANALYZE before showing all counts correctly !

Display a block of text: multi-line grep with perl
-n reads input, line by line, in a loop sending to $_ Equivalent to while () { mycode } -e execute the following quoted string (i.e. do the following on the same line as the perl command) the elipses .. operator behaves like a range, remembering the state from line to line.

Command line progress bar
This command tar?s up a directory and sends the output to gzip, showing a rate of 223MB/s. This may require you installing the pv command. For debian based users out there: $ sudo aptitude install pv

Count number of files in a directory

get all Google ipv4 subnets for a iptables firewall for example
a bit shorter, parenthesis not needed but added for clarity

list files recursively by size

Short one line while loop that outputs parameterized content from one file to another
There is a common command for outputting a field or list of fields from each line in a file. Why wouldn't you just use cut?

See system users

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: