I use this in a script on my openwrt router to check if my DynDNS needs to be updated, saves your account from being banned for blank updates.

Strips the non-ip information from the dig output. Could be combined with "head -1" to ensure a single ip is returned. Useful for outputting as a variable for use in scripts.

Gets the internal and external IP addresses of all your interfaces, or the ones given as arguments

Will return your internal IP address.

Having to escape forwardslashes when using sed can be a pain. However, it's possible to instead of using / as the separator to use : .

I found this by trying to substitute $PWD into my pattern, like so

Of course, $PWD will expand to a character string that begins with a / , which will make sed spit out an error such as "sed: -e expression #1, char 8: unknown option to `s'".

So simply changing it to

did the trick.

Since the original command (#1873) didn't work on FreeBSD whose stat lacks the "-c" switch, I wrote an alternative that does. This command shows also the fourth digit of octal format permissions which yields the sticky bit information.

I use this as an alias:

alias authplain "printf '\!:1\0\!:1\0\!:2' | mmencode | tr -d '\n' | sed 's/^/AUTH PLAIN /'"

then..

# authplain someuser@somedomain.com secretpassword

AUTH PLAIN c29tZXVzZXJAc29tZWRvbWFpbi5jb20Ac29tZXVzZXJAc29tZWRvbWFpbi5jb20Ac2VjcmV0cGFzc3dvcmQ=

#

I wanted all the 'hidden' .flv files from the http link in the command line; wget seemed appropriate, fed with output from lynx, grep the flv files and the normalised via sed (to remove the numeric bullet). Similar to the 'Grab mp3 files' fu. Replace link with your own, grep arg with something more interesting ;) See here for something along the same lines...

http://www.commandlinefu.com/commands/view/1006/grab-mp3-files-from-your-favorite-netcasts-mp3blog-or-sites-that-often-have-good-mp3s

Hope you find it useful! Improvements welcome, naturally.

Useful if you f.i. want to block/allow all connections from a certain provider which uses successive netnames for his ip blocks. In this example I used the german Deutsche Telekom which has DTAG-DIAL followed by a number as netname for the dial in pools.

There are - as always ;) - different ways to do this. If you have seq available you can use

or without seq you can use bash brace expansion

or if you like while better than for use something like

and so on.

Strangely enough, there is no option --lines=[negative] with tail, like the head's one, so we have to use sed, which is very short and clear, you see.

Strangely more enough, skipping lines at the bottom with sed is not short nor clear. From Sed one liner :

# delete the last 10 lines of a file

$ sed -e :a -e '$d;N;2,10ba' -e 'P;D' # method 1

$ sed -n -e :a -e '1,10!{P;N;D;};N;ba' # method 2

When you've got a list of numbers each on its row, the ECHO command puts them on a simple line, separated by space. You can then substitute the spaces with an operator. Finally, pipe it to the BC program.

I'm pretty sure everyone has curl and sed, but not everyone has lynx.

Display the amount of memory used by all the httpd processes. Great in case you are being Slashdoted!

slashdot.org webserver adds an X-Bender or X-Fry HTTP header to every response!

On a Gentoo system, this command will tell you which packets you have installed and sort them by how much space they consume. Good for finding out space-hogs when tidying up disk space.

Useful for deleting old unused log files.