Commands by penpen (13)

  • Today I learned that is not a alone in its conquest for further the knowledge about the command line. Allow me to introduce you to

    penpen · 2009-08-20 11:47:35 2
  • Using DynDNS or a similar service not only allows access to your home machine from outside without needing to know what IP the ISP has assigned to it but it also comes in handy if you want to know your external IP address. The only purpose of the sed command is to remove the leading " has address " part from the output. If you don't need to discard it you can simply use host $HOSTNAME

    host $HOSTNAME|cut -d' ' -f4
    penpen · 2009-08-08 12:39:00 2
  • To change to $HOME in that manner you need to set a shell option. In zsh it is auto_cd, hence setopt -o auto_cd in bash4 it is autocd, hence shopt -s autocd What the option does is allow you to cd to a directory by just entering its name. This also works if the directory name is stored in a variable: www=/var/www/lighttpd; $www sends you to /var/www/lighttpd. CAUTION: If a command or function name identical to the directory name exists it takes precedence.

    penpen · 2009-07-24 10:43:53 3
  • Depending on the installation only certain of these man pages are installed. 12 is left out on purpose because ISO/IEC 8859-12 does not exist. To also access those manpages that are not installed use opera (or any other browser that supports all the character sets involved) to display online versions of the manpages hosted at for i in $(seq 1 11) 13 14 15 16; do opera$i.7.html; done

    for i in $(seq 1 11) 13 14 15 16; do man iso-8859-$i; done
    penpen · 2009-03-31 19:40:15 1
  • Let me suggest using wget for obtaining the HTTP header only as the last resort because it generates considerable textual overhead. The first ellipsis of the sample output stands for Spider mode enabled. Check if remote file exists. --2009-03-31 20:42:46-- Resolving Connecting to||:80... connected. HTTP request sent, awaiting response... and the second one looks for Length: 438 [text/html] Remote file exists and could contain further links, but recursion is disabled -- not retrieving. Show Sample Output

    wget --server-response --spider
    penpen · 2009-03-31 18:49:14 6
  • Without the -dump option the header is displayed in lynx. You can also use w3m, the command then is w3m -dump_head Show Sample Output

    lynx -dump -head
    penpen · 2009-03-31 18:41:36 1
  • In the above example 'muspi merol' (the output of the first rev command) is sent to stderr and 'lorem ipsum' (the output of the second rev command) is sent to stdout. rev reverse lines of a file or files. This use of tee allows testing if a program correctly handles its input without using files that hold the data. Show Sample Output

    rev <<< 'lorem ipsum' | tee /dev/stderr | rev
    penpen · 2009-03-31 13:12:09 2
  • rot13 maps (A..MN..Z) to ( and so does this alias.

    alias rot13="tr '[A-Za-z]' '[N-ZA-Mn-za-m]'"
    penpen · 2009-03-30 19:08:49 2
  • An improved version of that uses Perl to pretty-print the output. Note that the GNU-style '--no-title' option has been replaced by its one-letter counterpart '-t'. Show Sample Output

    watch -tn1 'bc<<<"`date -d'\''friday 21:00'\'' +%s`-`date +%s`"|perl -ne'\''@p=gmtime($_);printf("%dd %02d:%02d:%02d\n",@p[7,2,1,0]);'\'
    penpen · 2009-03-29 19:53:36 3
  • Here $HOME/shots must exist and have appropriate access rights and sitecopy must be correctly set up to upload new screen shots to the remote site. Example .sitecopyrc (for illustration purposes only) site shots server username user password antabakadesuka local /home/penpen/shots remote public_html/shots permissions ignore The command uses scrot to create a screen shot, moves it to the screen shot directory, uploads it using screen uses xsel to copy the URL to the paste buffer (so that you can paste it with a middle click) and finally uses feh to display a preview of the screen shot. Note that $BASE stands for the base URL for the screen shots on the remote server, replace it by the actual location; in the example would be fitting. Assign this command to a key combination or an icon in whatever panel you use. Show Sample Output

    scrot -e 'mv $f \$HOME/shots/; sitecopy -u shots; echo "\$BASE/$f" | xsel -i; feh `xsel -o`'
    penpen · 2009-03-26 12:08:39 0
  • A web server using $HOME/public_html as user directory is required, $HOME/public_html/shots must exist and have appropriate access rights and $HOSTNAME must be known to and accessible from the outside world. The command uses scrot to create a screen shot, moves it to the screen shot directory, uses xsel to copy the URL to the paste buffer (so that you can paste it with a middle click) and finally uses feh to display a preview of the screen shot. Assign this command to a key combination or an icon in whatever panel you use.

    scrot -e 'mv $f \$HOME/public_html/shots/; echo "http://\$HOSTNAME/~\$USER/shots/$f" | xsel -i; feh `xsel -o`'
    penpen · 2009-03-26 11:32:09 1
  • Have netcat listen on port 8000, point browser to http://localhost:8000/ and you see the information sent. netcat terminates as soon as your browser disconnects. I tested this command on my Fedora box but linuxrawkstar pointed out that he needs to use nc -l -p 8000 instead. This depends on the netcat version you use. The additional '-p' is required by GNU netcat that for example is used by Debian but not by the OpenBSD netcat port used by my Fedora system. Show Sample Output

    nc -l 8000
    penpen · 2009-03-25 23:09:38 2
  • 'watch' repeatedly (default every 2 seconds, -n 1 => every second) runs a command (here ':', a shorthand for 'true'), displays the output (here nothing) and the date and time of the last run. I thought it to be obvious but it seemingly is not: to exit use Ctrl-C.

    watch -n 1 :
    penpen · 2009-03-25 23:00:28 1

What's this? 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

Copy text to the clipboard
Great for little scripts that dig up obscure info that you are going to have to paste into another app anyway.

Show an application's environment variables

ls -qahlSr # list all files in size order - largest last
I find it useful, when cleaning up deleting unwanted files to make more space, to list in size order so I can delete the largest first. Note that using "q" shows files with non-printing characters in name. In this sample output (above), I found two copies of the same iso file both of which are immediate "delete candidates" for me.

Convert "man page" to text file
You can convert any UNIX man page to .txt

Create a mirror of a local folder, on a remote server
Create a exact mirror of the local folder "/root/files", on remote server 'remote_server' using SSH command (listening on port 22) (all files & folders on destination server/folder will be deleted)

Restrict the use of dmesg for current user/session
Linux offers an interesting option to restrict the use of dmesg. It is available via /proc/sys/kernel/dmesg_restrict. You can check the status with: $ cat /proc/sys/kernel/dmesg_restrict Alternatively you can use sysctl: $ sudo sysctl -w kernel.dmesg_restrict=1 To make your change persistent across reboot, edit a fille in /etc/sysctl.d/.

Rename files in batch

Make directory including intermediate directories
This will create the intermediate directories that do not exist. I did not know about this for a long time.

convert .bin / .cue into .iso image
bchunk [-v] [-p] [-r] [-w] [-s]

Get absolut path to your bash-script
Another way of doing it that's a bit clearer. I'm a fan of readable code.

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.


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: