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

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Check syntax of all Perl modules or scripts underneath the current directory
Finds all *.p[ml]-files and runs a perl -c on them, checking whether Perl thinks they are syntactically correct

Inverted cowsay
It's quite fun to invert text using "" (ref: ). Slightly more challenging is to flip a whole "cowsay". :-)

To print a specific line from a file
Just one character longer than the sed version ('FNR==5' versus -n 5p). On my system, without using "exit" or "q", the awk version is over four times faster on a ~900K file using the following timing comparison: $ testfile="testfile"; for cmd in "awk 'FNR==20'" "sed -n '20p'"; do echo; echo $cmd; eval "$cmd $testfile"; for i in {1..3}; do time for j in {1..100}; do eval "$cmd $testfile" >/dev/null; done; done; done Adding "exit" or "q" made the difference between awk and sed negligible and produced a four-fold improvement over the awk timing without the "exit". For long files, an exit can speed things up: $ awk 'FNR==5{print;exit}'

Exclude inserting a table from a sql import
Starting with a large MySQL dump file (*.sql) remove any lines that have inserts for the specified table. Sometimes one or two tables are very large and uneeded, eg. log tables. To exclude multiple tables you can get fancy with sed, or just run the command again on subsequently generated files.

Shows the torrent file name along with the trackers url
Replace * with any filename matching glob or an individual filename

Sort the current buffer in vi or vim.
vim 7 or higher has internal sort, too 'sort n' for numbers

Stream youtube videos
Streams youtube-dl video to mplayer. Usage: syt '' '' Uses mplayer controls

list block devices
Shows all block devices in a tree with descruptions of what they are.

Generate a binary file with all ones (0xff) in it
This is similar to how you would generate a file with all zeros $ dd if=/dev/zero of=allzeros bs=1024 count=2k

Bind a key with a command
the -x option is for binding to a shell command

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