Does Select-Object -First terminate native executable processes in the pipeline?

Answer

Select-Object -First does not send a termination signal to the upstream process. It stops reading from the pipeline after receiving the requested number of objects, which closes its read end of the pipe.

Confirmed facts

• When the read end of a pipe is closed, the operating system reports a broken‑pipe condition (ERROR_BROKEN_PIPE on Windows, SIGPIPE on Unix) on subsequent write attempts.
• Both Windows PowerShell 5.1 and PowerShell 7.x rely on this OS mechanism; they do not add any extra termination signal.

Likely explanation

If the native executable checks the result of each write and exits when the write fails, it will terminate shortly after Select-Object -First satisfies its request. If it ignores write errors or buffers output, it may continue running until it attempts to write more data and encounters the error.

Steps to verify for your case

1. Create or obtain a small test program that writes a line to STDOUT every second, checks the write result, and exits on failure.
2. Run . estprogram.exe | Select-Object -First 2 and observe whether the process exits after two lines (you can check with Get-Process or the program’s exit code).
3. Repeat with a variant that ignores write errors to see if the process stays alive despite the closed pipe.

Missing diagnostic detail

To give a definitive recommendation, we need to know whether the native executable you are piping checks the success of its write operations and terminates on failure. If it does, the process will likely stop early; if it does not, it may continue until it attempts further output.