2

两者之间的确切区别是什么:

if [ $? -ne 0 ];

if [[ $? -ne 0 ]];
4

2 回答 2

3

如此处所述:

相反[[[防止变量值的分词。因此,如果 VAR="var with spaces",您不需要$VAR在测试中使用双引号 - 即使使用引号仍然是一个好习惯。此外,[[防止路径名扩展,因此带有通配符的文字字符串不会尝试扩展为文件名。使用[[,==并将!=右侧的字符串解释为要与左侧的值匹配的 shell glob 模式,例如:[[ "value" == val* ]].

于 2012-06-29T04:28:37.437 回答
2

空无一人。不过,[[...]]语法介绍了您可以使用条件表达式执行的其他一些操作。来自help [[

Returns a status of 0 or 1 depending on the evaluation of the conditional
expression EXPRESSION.  Expressions are composed of the same primaries used
by the `test' builtin, and may be combined using the following operators:

  ( EXPRESSION )    Returns the value of EXPRESSION
  ! EXPRESSION              True if EXPRESSION is false; else false
  EXPR1 && EXPR2    True if both EXPR1 and EXPR2 are true; else false
  EXPR1 || EXPR2    True if either EXPR1 or EXPR2 is true; else false

When the `==' and `!=' operators are used, the string to the right of
the operator is used as a pattern and pattern matching is performed.
When the `=~' operator is used, the string to the right of the operator
is matched as a regular expression.
于 2012-06-29T04:26:05.973 回答