$ my-num=1
my-num=1: command not found
$ mynum=1
我想知道为什么第一次作业失败了?
为什么bash认为它是一个命令?
-
bash 中有一些特殊字符吗?
谢谢。
答案1
POSIX 标准规定如下:
3.229 Name
In the shell command language, a word consisting solely of underscores, digits, and
alphabetics from the portable character set. The first character of a name is not a digit.
在 Shell 语法规则的 POSIX 标准部分中,它指出:
7. [Assignment preceding command name]
a. [When the first word]
If the TOKEN does not contain the character ’=’, rule 1 is applied.
Otherwise, 7b shall be applied.
b. [Not the first word]
If the TOKEN contains the equal sign character:
— If it begins with ’=’, the token WORD shall be returned.
— If all the characters preceding ’=’ form a valid name (see XBD Section 3.229, |
on page 65), the token ASSIGNMENT_WORD shall be returned. (Quoted
characters cannot participate in forming a valid name.)
— Otherwise, it is unspecified whether it is ASSIGNMENT_WORD or WORD
that is returned.
Assignment to the NAME shall occur as specified in Section 2.9.1 (on page 2263).
由于变量名称包含无效字符,因此它不会尝试赋值,而是将其视为简单命令。