Commands by rxw (2)

  • Check if SSH tunnel is open and open it, if it isn't. NB: In this example, 3333 would be your local port, 5432 the remote port (which is, afaik, usually used by PostgreSQL) and of course you should replace REMOTE_HOST with any valid IP or hostname. The example above let's you work on remote PostgreSQL databases from your local shell, like this: psql -E -h localhost -p 3333


    -1
    while true; do nc -z localhost 3333 >|/dev/null || (ssh -NfL 3333:REMOTE_HOST:5432 USER@REMOTE_HOST); sleep 15; done
    rxw · 2015-09-21 02:25:49 1
  • Online games have pretty good lag compensation nowadays, Sometimes though, you really want to get some warning about your latency, e.g. while playing Diablo III in Hardcore mode, so you know when to carefully quit the game b/c your flatmate started downloading all his torrents at once. This is done on Darwin. On Linux/*nix you would need to find another suitable command instead of `say` to spell out your latency. And I used fping because it's a little bit easier to get the latency value needed. Something similar with our regular ping command could look like this: while :; do a=$(ping -c1 google.com | grep -o 'time.*' | cut -d\= -f2 | cut -d\ -f1 | cut -b1-4); [[ $a > 40 ]] && say "ping is $a"; sleep 3; done


    0
    while :; do a=$(fping -e google.de | grep -o '[0-9]+.[0-9]+'); [[ $a > 40 ]] && say "ping is $a"; sleep 3; done
    rxw · 2015-09-21 02:14:02 0

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

Set laptop display brightness
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video). $ cat /proc/acpi/video/VGA/LCD/brightness to discover the possible values for your display.

uniq without pre-sorting
Reads stdin, and outputs each line only once - without sorting ahead of time. This does use more memory than your system's sort utility.

Preview of a picture in a terminal
This command allows you to see a preview of a picture via the terminal. It can be usefull when you are ssh'ing your server without X-forwarding. To have en example of the output you can get with this command see http://www.vimeo.com/3721117 Download at http://inouire.net/image-couleur.html Sources here: http://inouire.net/archives/image-couleur_source.tar.gz

Remove empty directories
You can also use, $ find . -depth -type d -exec rmdir {} \; 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"

Double your disk read performance in a single command
(WARN) This will absolutely not work on all systems, unless you're running large, high speed, hardware RAID arrays. For example, systems using Dell PERC 5/i SAS/SATA arrays. If you have a hardware RAID array, try it. It certainly wont hurt. You may be can test the speed disk with some large file in your system, before and after using this: $ time dd if=/tmp/disk.iso of=/dev/null bs=256k To know the value of block device parameter known as readahead. $ blockdev --getra /dev/sdb And set the a value 1024, 2048, 4096, 8192, and maybe 16384... it really depends on the number of hard disks, their speed, your RAID controller, etc. (see sample)

Save your terminal commands in bash history in real time
Use this command if you want your terminal commands be saved in your history file in real time instead of waiting until the terminal is closed

Image to color palette generator
Extract a color palette from a image useful for designers. Example usage: $extract-palette myawesomeimage.jpg 4 Where the first argument is the image you want to extract a palette from. The second argument is the number of colors you want. It may be the case where you want to change the search space. In that case, change the -resize argument to a bigger or smaller result. See the ImageMagick documentation for the -resize argument.

Execute a command at a given time
This is an alternative to cron which allows a one-off task to be scheduled for a certain time.

Show highlighted text with full terminal width
Show a full terminal line inverted with custom text.


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: