如何检查Bash中最后一个字符串字符是否等于'*'? [英] How to check if the last string character equals '*' in Bash?

问题描述

我需要检查路径是否包含'*'字符作为最后一位数字.

I need to check if a path contains the '*' character as last digit.

我的方法:

length=${#filename}
((filename--))
#use substring to get the last character
if [ ${img:$length:1} == "*"] ;then
   echo "yes"
fi

这将返回 [: too many arguments 错误.

This returns the [: too many arguments error.

我在做什么错了?

推荐答案

[ "${filename:$length:1}" == "*" ] && echo yes

在您的帖子中，"*"和]之间没有空格.这使bash感到困惑.如果语句以[开头，则bash坚持要求其最后一个参数为].没有空格，最后一个参数是"*"]，在删除引号后，它变为*]，而不是].

In your post, there was no space between "*" and ]. This confuses bash. If a statement begins with [, bash insists that its last argument be ]. Without the space, the last argument is "*"] which, after quote removal, becomes *] which is not ].

将它们放在一起:

length=${#filename}
((length--))
[ "${filename:$length:1}" == "*" ] && echo yes

更多:根据下面的评论，以上三行可以简化为:

MORE: As per the comments below, the three lines above can be simplified to:

[ "${filename: -1}" == "*" ] && echo yes

-1是获取最后一个字符的简写.另一种可能性是:

The -1 is shorthand for getting the last character. Another possibility is:

[[ $filename = *\* ]] && echo yes

这使用了bash更强大的条件测试[[.上面的代码查看$filename是否与glob模式*\*相匹配，其中第一个星号表示任何字符中的零个或多个"，而后两个字符\*表示字面上的星形字符.因此，以上测试文件名是否以文字*结尾.使用[[解决此问题的另一种方法可以在@broslow的答案中找到.

This uses bash's more powerful conditional test [[. The above sees if $filename is matches the glob pattern *\* where the first star means "zero or more of any character" and the last two characters, \*, mean a literal star character. Thus, the above tests for whether filename ends with a literal *. Another solution to this problem using [[ can be found in @broslow's answer.

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