Spawn of a Shell - Handling Sub Processes - Jordan Borean - PSConfEU 2026

PowerShell Conference EU June 1-4, 2026 Dorint Pallas Wiesbaden https://github.com/psconfeu/2026 (slides, code) Jordan introduces the session by explaining that he works at Red Hat on Ansible, with a focus on Windows content and PowerShell. He then outlines the talk’s main topic: the many ways to start and manage subprocesses in PowerShell, and why this area often causes confusion. He begins with process invocation methods, comparing direct invocation, the call operator, relative and absolute paths, and the use of variables in paths. He also explains dot sourcing, jobs, and Start-Process, and shows when each approach creates a new process, when it blocks, and when it does not. A central part of the session covers Invoke-Expression, which Jordan strongly advises against. He demonstrates how it can break when paths contain spaces and how it can execute unintended code when user input is embedded into a command string. He contrasts this with the safer use of the call operator. Jordan then turns to command-line argument handling, describing differences between Windows and non-Windows platforms. He explains how PowerShell binds arguments, how quoting is applied, and how tracing can help inspect parameter binding. He also covers arrays, splatting, and the differences between legacy, standard, and Windows argument-passing modes. The talk next focuses on standard input, output, and error streams. Jordan explains that native processes exchange bytes rather than PowerShell objects, so encoding matters. He discusses output encoding, raw byte handling, redirection, and how to capture output and error streams separately. Finally, he covers exit codes and how PowerShell handles them. He explains that non-zero exit codes are not treated as failures by default, and shows ways to check them manually or make PowerShell stop on failure. He ends by introducing a PowerShell mini-shell technique that uses script blocks and serialized objects, and notes that command-line size limits can become a problem. Chapters: 00:00:00 Spawn of a Shell - Handling Sub Processes - Jordan Borean - PSConfEU 2026 00:00:15 Introduction and Speaker Background 00:01:14 PowerShell Process Invocation 00:05:42 Why Invoke-Expression Fails 00:08:41 Blocking and GUI Processes 00:10:15 Waiting on Child Processes 00:11:42 Running Consoles in Background 00:14:27 Command-Line Argument Quirks 00:19:33 Escaping Rules and Passing Modes 00:22:47 Stop Processing and Splatting 00:25:48 Standard Input and Output 00:30:19 Encoding Output Correctly 00:32:30 Capturing Streams Separately 00:32:54 Raw Bytes Between Processes 00:35:02 JSON for Structured Output 00:36:21 Exit Codes and Failures 00:43:44 PowerShell Mini-Shell 00:46:23 Command Line Limits