Operating system functions.
System.os.posix: Common POSIX functions and constants.args: Arguments passed in from the shell.dylib_extension: The dynamic library extension on this system.chdir(newcwd): Changes the current working directory.newcwd: The directory to change to.chmod(name, permission): Changes permissions for a file or directory.name: The file/directory to modify.permission: The permissions to set (e.g. 0755)envGet(var): Retrieve contents of environment variable.var: Environment variable to return.envSet(var, val): Set contents of environment variable to given value.var: Variable to set.val: Value to set variable to.fork(): Forks off a new process.getcwd(): Gets the current working directory.mkdir(name): Creates a new directory.name: The directory to create.rmdir(name): Removes a directory.name: The directory to remove.system(cmd): Executes system command.cmd: Command to execute.