Executing an external command.

This module provides a simple interface for executing external commands. For a more complex, but more powerful, interface, see the System.Process module.

Computation system cmd returns the exit code produced when the operating system processes the command cmd.

This computation may fail with

• PermissionDenied: The process has insufficient privileges to perform the operation.
• ResourceExhausted: Insufficient resources are available to perform the operation.
• UnsupportedOperation: The implementation does not support system calls.

On Windows, system is implemented using Windows's native system call, which ignores the SHELL environment variable, and always passes the command to the Windows command interpreter (CMD.EXE or COMMAND.COM), hence Unixy shell tricks will not work.

The computation rawSystem cmd args runs the operating system command cmd in such a way that it receives as arguments the args strings exactly as given, with no funny escaping or shell meta-syntax expansion. It will therefore behave more portably between operating systems than system.

The return codes and possible failures are the same as for system.