From GridLAB-D Wiki
#system - Execute a command in an operating system shell
Synopsis
#system command
Remarks
The shell executes command and the return value is assigned to the return_code global variable.
If the system() call used to execute the command returns either 127 or -1, the call is deemed to have failed and the GLM loader fails. Any other return code is regarded as having been a successful call, even if the return code is non-zero.
Caveat
Shell commands are almost by definition not portable. Users seeking portable models should avoid using system in a GLM files.
Version
The system macro was introduced in https://sourceforge.net/p/gridlab-d/code//2996 and is targeted for Hassayampa (Version 3.0).