After gsh parses the command-line, it will then execute the command and pass any arguments to the command. If, however, the command does not exist, gsh will report an error. The reason the command does not exist could be either the command name was typed wrong or the command does not exist.
$0 represents the command to be executed. Either the command name was entered incorrectly or the command does not exist. Recheck the spelling of the command and check $PATH to make sure the command exists in the pathname list.
$0 represents the command to be executed. Check to ensure that the filetype is correct.
Redirection was specified but the command-line had no command.
An error was encountered forking a process. The most likely culprit is there are too many processes running.