Check These Out
Fool date by setting the timezone out by 24 hours and you get yesterday's date. Try TZ=XYZ-24 to get tomorrow's date. I live in TZ=GMT0BST so you might need to shift the number 24 by the hours in your timezone.
Create a encrypted tar.gz file from a directory on the fly. The encryption is done by GPG with a public key. The resulting filename is tagged with the date of creation. Very usefull for encrypted snapshots of folders.
This will create an exact duplicate image of your hard drive that you can then restore by simply reversing the "if" & "of" locations.
$ sudo dd if=/media/disk/backup/sda.backup of=/dev/sda
Alternatively, you can use an SSH connection to do your backups:
$dd if=/dev/sda | ssh user@ssh.server.com dd of=~/backup/sda.backup
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
works best in a shell script run at startup. It will ping localhost once and output to null, after it does that, acpi is called for temperature in fahrenheit and piped through to another loop that feeds notify-send for a tooltip. After waiting five minutes, it will start over.
man tcptraceroute
Just how much space are those zillions of database logs taking up ? How much will you gain on a compression rate of say 80% ? This little line gives you a good start for your calculations.
If you use 'tail -f foo.txt' and it becomes temporarily moved/deleted (ie: log rolls over) then tail will not pick up on the new foo.txt and simply waits with no output.
'tail -F' allows you to follow the file by it's name, rather than a descriptor. If foo.txt disappears, tail will wait until the filename appears again and then continues tailing.
This command creates a rar archive from all files in the current folder and names the archive after the folder name.
