Tip #2: waitfor.exe
waitfor.exe a in-box tool that waits or sends a signal.
waitfor.exe is a windows built-in tool, that lets you send signals and it can wait for signals even over the network. So, that’s 😎 and all, but for what can it be used for.
Let’s say you have long-running script/task/batch and you want to react upon completion (or in between) with another script. There are sure thousands of ways of doing so, but I found this quite useful, as you can LotL1 waitfor.exe on Windows.
Let me illustrate this with an example:
Receive signal script (receive.bat)
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echo Waiting for baton1
waitfor baton1
echo baton1 received
Send signal script (send.bat)
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echo Pass baton1
waitfor /si baton1
You would first start receive.bat and then send.bat. The waitfor baton1 would pause the receive.bat, until send.bat sends waitfor /si baton1
Some examples where this can be useful:
- copy jobs
- backup jobs
- setup’s
- etc…
Protocol
The tool is based on SMB mail slot listening on UDP 138. The send signal is broadcasted unless a computer is specified, e.g. waitfor /s targetdevicename /si baton1. Which means, if you send a signal e.g. waitfor /si baton1, all devices in your broadcast domain that are waiting for the signal baton1, e.g. waitfor baton1 would receive it.
Wireshark capture of SMB mail slot
Footnotes
Living of the Land –> inbox ↩︎