$ @在shell脚本中是什么意思？

Question

@在shell脚本中，美元符号后跟at符号（）是什么意思？例如：umbrella_corp_options $@

Answer 1

$@与几乎相同$*，均表示“所有命令行参数”。它们通常用于简单地将所有参数传递给另一个程序（从而形成对该另一个程序的包装）。

当您的参数中带有空格（例如）并$@用双引号引起来时，两种语法之间的差异就会显现出来：

wrappedProgram "$@"

# ^^^ this is correct and will hand over all arguments in the way

#     we received them, i. e. as several arguments, each of them

#     containing all the spaces and other uglinesses they have.

wrappedProgram "$*"

# ^^^ this will hand over exactly one argument, containing all

#     original arguments, separated by single spaces.

wrappedProgram $*

# ^^^ this will join all arguments by single spaces as well and

#     will then split the string as the shell does on the command

#     line, thus it will split an argument containing spaces into

#     several arguments.

示例：呼叫

wrapper "one two    three" four five "six seven"

将导致：

"$@": wrappedProgram "one two    three" four five "six seven"

"$*": wrappedProgram "one two    three four five six seven"

                             ^^^^ These spaces are part of the first

                                  argument and are not changed.

$*:   wrappedProgram one two three four five six seven

Answer 2

$@在大多数情况下，使用纯手段“会尽最大努力伤害程序员”，因为在大多数情况下，这会导致单词分隔以及参数中的空格和其他字符出现问题。

在（被猜测的）所有情况的99％中，要求将其括在"："$@"是可用于可靠地遍历参数的内容。

for a in "$@"; do something_with "$a"; done