IBM's CMS Operating System, which is a single-user operating system which runs as a guest under IBM's VM Hypervisor, has an interesting file-structure.
Files consist of three elements, File Name, File Type, and File Mode. The File Mode consists of two elements, a single alphabetic, which for ease of explanation can be regarded in a similar way to the Drive Letter for Windows/MS-DOS, and a single numeric digit.
The single numeric digit has meaning, http://publib.boulder.ibm.com/infocenter/zvm/v5r4/index.jsp?topic=/com.ibm.zvm.v54.dmsa3/hcsd0b10127.htm, and for this task it is the number 3 which is interesting:
File Mode Number 3
File mode number 3 means that files are erased after they are read. You can use file mode number 3 if you do not want to maintain
copies on your minidisks or in your SFS directories.
So, spend hours writing your script and file it as `LOST FOREVER A3'. Run it, it works first time. Set off home, job well done.
Note, no message is produced indicating the erasure. After all, everyone knows what that
3 means, don't they?
It is actually of course very useful. You can, once testing is complete, use the
3 for temporary files, and not have to clean up afterwards, because they are read-once files.
viin a single terminal environment has this effect, no escape from it unless you reboot :) Just a joke here. \$\endgroup\$
echo "If you try to execute me again, it means you are an idiot.";<-- Nobody will execute more than once :P \$\endgroup\$