如何检查最后一个字符串字符是否等于 Bash 中的“*”？
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How to check if the last string character equals '*' in Bash?
提问by JonaSc
I need to check if a path contains the '*' character as last digit.
我需要检查路径是否包含“*”字符作为最后一位数字。
My approach:
我的做法：
length=${#filename}
((filename--))
#use substring to get the last character
if [ ${img:$length:1} == "*"] ;then
echo "yes"
fi
This returns the [: too many argumentserror.
这将返回[: too many arguments错误。
What am I doing wrong?
我究竟做错了什么？
回答by John1024
[ "${filename:$length:1}" == "*" ] && echo yes
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 ].
在您的帖子中，"*"和之间没有空格]。这会混淆 bash。如果语句以 开头[，bash 坚持其最后一个参数是]。如果没有空格，最后一个参数是"*"]which 在去除引号后变成*]which is not ]。
Putting it all together:
把它们放在一起：
length=${#filename}
((length--))
[ "${filename:$length:1}" == "*" ] && echo yes
MORE:As per the comments below, the three lines above can be simplified to:
更多：根据下面的评论，上面的三行可以简化为：
[ "${filename: -1}" == "*" ] && echo yes
The -1is shorthand for getting the last character. Another possibility is:
该-1是简写形式，得到的最后一个字符。另一种可能是：
[[ $filename = *\* ]] && echo yes
This uses bash's more powerful conditional test [[. The above sees if $filenameis matches the glob pattern *\*where the first star means "zero or more of any character" and the last two characters, \*, mean a literal star character. Thus, the above tests for whether filename ends with a literal *. Another solution to this problem using [[can be found in @broslow's answer.
这使用了 bash 更强大的条件测试[[。上面查看是否$filename与 glob 模式匹配，*\*其中第一个星号表示“零个或多个任何字符”，最后两个字符\*, 表示文字星号字符。因此，上述测试文件名是否以文字结尾*。[[可以在@broslow 的回答中找到使用此问题的另一种解决方案。
回答by Reinstate Monica Please
Just use regex
只需使用正则表达式
if [[ "$filename" =~ '*'$ ]]; then
echo "yes"
fi
Couple of issues in your syntax.
您的语法中有几个问题。
- You need a space before the last
] - Make sure to quote variables inside single brackets
${variable:${#variable}:1}won't return any characters,${variable:$((${#variable}-1))}should work (note though the 1 length at the end is redundant)
- 在最后一个之前需要一个空格
] - 确保在单括号内引用变量
${variable:${#variable}:1}不会返回任何字符，${variable:$((${#variable}-1))}应该可以工作（请注意，尽管末尾的 1 长度是多余的）
