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Get rid from a blank display without reboot
Killall5 will kill your session and redirect to login screen. -Very useful when suffering display problems. -Can use F1-F6 -Need to login in the particular console if not already

Buffer in order to avoir mistakes with redirections that empty your files
A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file. It can be easily avoided because of : 1) warnings "-bash: file.txt: cannot overwrite existing file" 2) options (often "-i") that let the command directly modify the file but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file. Lots of things could probably done in a better way, if you know one...

rotate a one page pdf to 90 Degrees Clockwise
This can be taken from the pdftk docs http://www.pdflabs.com/docs/pdftk-man-page/ http://www.pdflabs.com/docs/pdftk-cli-examples/ , but the command examples are not simple.

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"

check the status of 'dd' in progress (OS X)
Your platform may not have pv by default. If you are using Homebew on OSX, simply 'brew install pv'.

Create arbitrary big file full of zeroes but done in a second
If you want to create fast a very big file for testing purposes and you do not care about its content, then you can use this command to create a file of arbitrary size within less than a second. Content of file will be all zero bytes. The trick is that the content is just not written to the disk, instead the space for it is somehow reserved on operating system level and file system level. It would be filled when first accessed/written (not sure about the mechanism that lies below, but it makes the file creation super fast). Instead of '1G' as in the example, you could use other modifiers like 200K for kilobytes (1024 bytes), 500M for megabytes (1024 * 1024 bytes), 20G for Gigabytes (1024*1024*1024 bytes), 30T for Terabytes (1024^4 bytes). Also P for Penta, etc... Command tested under Linux.

Get all ip address for the host

Extract all of the files on an RPM on a non-RPM *nix

Show line numbers in a text file

Process command output line by line in a while loop
This snippet allows to process the output of any bash command line by line.

Stay in the loop…

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