> err 0xC0000005 # for hex 0xc0000005 / decimal -1073741819 STATUS_ACCESS_VIOLATION Check against Win32 error codes:
In the seemingly sterile output of a command-line program—a lone integer returned to the operating system—lies a sophisticated, often misunderstood contract between a process and its caller. On Windows, this integer is the exit code (or "return code"), and while the convention 0 for success and non-zero for failure is universal, the depth beneath is uniquely shaped by Windows' architecture, its legacy subsystems, and the perils of cross-platform assumptions. 1. The Kernel's Handshake: How Exit Codes Really Work When a Windows process terminates—whether by returning from main() , calling ExitProcess() , or suffering an unhandled exception—the kernel records a 32-bit unsigned integer inside the EPROCESS block. This value persists until the process object is reaped by WaitForSingleObject() or GetExitCodeProcess() . exit codes windows
This layering leads to a key insight: . The default for a thread is STATUS_THREAD_TERMINATED (0x00000100); for a process, it is STATUS_PENDING (0x00000103) until termination, then the final code. 2. The Semantic Wasteland: What Does Non-Zero Mean? Unlike Unix, where exit codes are small (0–255) and often mapped to sysexits.h conventions, Windows exit codes are full 32-bit values, blending several distinct categories: > err 0xC0000005 # for hex 0xc0000005 /
PowerShell-native commands return rich objects, not exit codes. When you run an external .exe , PowerShell captures its exit code in $LASTEXITCODE , but the PowerShell process's own exit code is set only by exit $n . A script that runs non-existent.exe will see $LASTEXITCODE = 0xC0000135 (STATUS_DLL_NOT_FOUND), but the PowerShell process itself exits with 0 unless you explicitly forward it. 4. The Debugger's Compass: Interpreting Exit Codes as Clues For a systems engineer, an unexpected exit code is a compressed diagnostic. Here’s how to decompress it: The Kernel's Handshake: How Exit Codes Really Work
This overlap is a trap: an exit code of 2 could mean "invalid parameter" (application-defined), or it could mean ERROR_FILE_NOT_FOUND from a failed CreateFile . Without the program's documentation, you cannot disambiguate. Three common scenarios produce exit codes that are technically correct but semantically useless: