Simple Commands (Bash Reference Manual)
3.2.2 Simple Commands
A simple command is the kind of command encountered most often. It’s just a sequence of words separated by
blanks, terminated by one of the shell’s control operators (see Definitions). The first word generally specifies a command to be executed, with the rest of the words being that command’s arguments.
The return status (see Exit Status) of a simple command is its exit status as provided by the POSIX 1003.1
waitpid function, or 128+
n if the command was terminated by signal