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clean up memory on linux
where proc filesystem mounted under /proc

Add temporary entry to authorized_keys
If you frequently need to connect to your ubersecure mainframe from various uberunsafe machines, you have to face difficult decision: (a) type the password everytime during the session (lame), (b) add local public key to mainframes authorized_keys file (unsafe), (c) as above, but remove this key at the end of the session (pain in the a55). So let's say you save The Command to tempauth file in bin directory of your mainframe's account and make it executable. Then, while you're on one of these unsafe ones, do: $ cat $HOME/.ssh/id_rsa.pub|ssh 5z474n@mainframe.nl bin/tempauth 30 and password prompts stop the harassment for 30 minutes and you don't have to care to remove the unsafe key after that.

Flush and then immediately start watching a file
This is useful for keeping an eye on an error log while developing. The !^ pulls the first arg from the previous command (which needs to be run in a sub-shell for this shortcut to work).

Sort the size usage of a directory tree by gigabytes, kilobytes, megabytes, then bytes.
Since coreutils 7.6 provides sort -h

get diskusage of files modified during the last n days
get diskusage of files (in this case logfiles in /var/log) modified during the last n days: $ sudo find /var/log/ -mtime -n -type f | xargs du -ch n -> last modified n*24 hours ago Numeric arguments can be specified as +n for greater than n, -n for less than n, n for exactly n. => so 7*24 hours (about 7 days) is -7 $ sudo find /var/log/ -mtime -7 -type f | xargs du -ch | tail -n1

Rename .JPG to .jpg recursively
Recursively rename .JPG to .jpg using standard find and mv. It's generally better to use a standard tool if doing so is not much more difficult.

What is my ip?

Produce a pseudo random password with given length in base 64
Don't copy trailing '=' or use head -c to limit to desired length.

Get a range on line with sed (first two)
Get the two first lines of a file and quit.

ssh tunnel with auto reconnect ability


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