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You could also pipe to logger.
optipng and advancecomp (for the the advpng and advdef tools) are the best FOSS tools for losslessly compressing PNGs. With the above tool chain, you can cut off as much as 20% off a PNG's file size.
If you spot a dubious looking cp command running you can use this command to view what is being copied and to where.
1234 is the PID of the cp command being passed to the lsof utility.
3r.*REG will display the file/directory that is being read/copied.
4w.*REG will display the destination it is being written to.
My netcat (nc-1.84-10.fc6) doesn't have the -e option, so I have to do it like this. Of course, instead of bash, you can use any executable, including scripts.
Do the same as pssh, just in shell syntax.
Put your hosts in hostlist, one per line.
Command outputs are gathered in output and error directories.
Cycles continuously through a string printing each character with a random delay less than 1 second. First parameter is min, 2nd is max. Example: 1 3 means sleep random .1 to .3. Experiment with different values. The 3rd parameter is the string. The sleep will help with battery life/power consumption.
$ cycle 1 3 $(openssl rand 100 | xxd -p)
Fans of "The Shining" might get a kick out of this:
$ cycle 1 4 ' All work and no play makes Jack a dull boy.'
Mirror the entire NASA Astronomy Picture of the Day archive, all the way from 1995. The archive is close to 2.5 GB, with lots of files, so give it some time. The logs can be redirected to a file using '-o somefile'. You might also want to try '-nH' and the '--cut-dirs' options
whowatch is a interactive, ncurses-based, process and users monitoring tool, which updates information in real time. This is a perfect tool for local and remote servers.
It displays information about the users currently logged on to the machine, in real-time. Besides standard information (login name, tty, host, user's process), the type of the connection (ie. telnet or ssh) is shown. Display of users command line can be switch to tty idle time.
Certain user can be selected and his processes tree may be viewed as well as tree of all system processes. Tree may be displayed with additional column that shows owner of each process. In the process tree mode SIGINT and SIGKILL signals can be sent to the selected process. Killing processes is just as simple and fun as deleting lines on the screen.