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 Chapter 2
[Definitions], page 3). 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 Section 3.7.5 [Exit Status], page 33) 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 n.

(BASH 官方参考手册 3.2.1)

*************

简单命令是最常用到的一类命令，它只有由 空格 分开的一个序列。一般，第一个字，指定的要运行的命令，后面接着的都是参数。例如：

echo $PATH $HOME