Resource tips and examples: Exec on Windows

Puppet can execute binaries (exe, com, bat, etc.), and can log the child process output and exit status. To ensure the resource is idempotent, specify one of the creates, onlyif, or unless attributes.

Since Puppet uses the same exec resource type on both *nix and Windows systems, there are a few Windows-specific caveats to keep in mind.

Command extensions

If a file extension for the command is not specified (for example, ruby instead of ruby.exe), Puppet will use the PATHEXT environment variable to resolve the appropriate binary. PATHEXT is a Windows-specific variable that lists the valid file extensions for executables.

Exit codes

On Windows, most exit codes should be integers between 0 and 2147483647.

Larger exit codes on Windows can behave inconsistently across different tools. The Win32 APIs define exit codes as 32-bit unsigned integers, but both the cmd.exe shell and the .NET runtime cast them to signed integers. This means some tools will report negative numbers for exit codes above 2147483647. (For example, cmd.exe reports 4294967295 as -1.) Since Puppet uses the GetExitCodeProcess Win32 API, it will report the very large number instead of the negative number, which might not be what you expect if you got the exit code from a cmd.exe session.

Microsoft recommends against using negative/very large exit codes, and you should avoid them when possible. To convert a negative exit code to the positive one Puppet will use, subtract it from 4294967296.

Shell built-ins

Puppet does not support a shell provider for Windows, so if you want to execute shell built-ins (e.g. echo), you must provide a complete cmd.exe invocation as the command. (For example, command => 'cmd.exe /c echo "foo"'.) When using cmd.exe and specifying a file path in the command line, be sure to use backslashes. (For example, 'cmd.exe /c type c:\path\to\file.txt'.) If you use forward slashes, cmd.exe will error.

Optional PowerShell exec provider

An optional PowerShell exec provider is available as a plugin and is is particularly helpful if you need to run PowerShell commands easily from within Puppet. To use it, install:

• The puppetlabs/powershell module

Inline PowerShell scripts

If you choose to execute PowerShell scripts using Puppet’s default exec provider on Windows, you must specify the remotesigned execution policy as part of the powershell.exe invocation:

exec { 'test':
  command => 'C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -executionpolicy remotesigned -file C:\test.ps1',
}