问题描述
这可能是一个非常愚蠢的问题，但是...如果[！ -n"$ 1"]的意思是，如果不超过1个参数，则......这样我就能知道它是如何工作的，但是-n是数字的缩写吗?我一直在阅读《高级bash编程指南》，他们只是开始使用它，我试图找到它，并提出它必须是内置"默认参数，第二个问题是是否有一个命令来显示默认值参数在Linux中.
This is probably a really dumb question, but... if [ ! -n "$1" ], means, if not more than 1 argument do... so I get how it works but what is -n is it the abbreviation of number?I've been reading through The Advanced bash programming guide and they just start using it, I've tried to find it and come up with it must be a "built-in" default parameter, second question is there a command to show default parameter's in Linux.
推荐答案
test(又名[)的-n参数表示不为空".您发布的示例的意思是如果$1不为空.这是说[ -z "$1" ];($1为空)的一种a回方式.
The -n argument to test (aka [) means "is not empty". The example you posted means "if $1 is not not empty. It's a roundabout way of saying [ -z "$1" ]; ($1 is empty).
您可以通过help test了解更多信息.
You can learn more with help test.
$1和其他($2，$3 ..)是位置参数.它们就是作为参数传递给您所在的脚本或函数的内容.例如，将名为foo的脚本作为./foo bar baz运行将导致$1 == bar，$2 == baz
$1 and others ($2, $3..) are positional parameters. They're what was passed as arguments to the script or function you're in. For example, running a script named foo as ./foo bar baz would result in $1 == bar, $2 == baz
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