在Bash中，为什么在函数中使用getopts只工作一次? [英] In Bash, why does using getopts in a function only work once?

问题描述

我正在尝试在macOS Sierra上创建一个简单的函数来计算字符串中的字符.可以正常工作(添加到我的bashrc文件中):

I'm trying to create a simple function on macOS Sierra that counts the characters in a string. This works fine (added to my bashrc file):

function cchar() {
    str=$1
    len=${#str}
    echo "string is $len char long"
}

$ cchar "foo"
string is 3 char long

我正在尝试使用-a选项对其进行扩展，因此我将其添加到了我的函数中(并注释掉了其余部分以进行测试):

I'm trying to expand it with a -a option, so I added this to my function (and commented the rest out for testing):

while getopts "a:" opt; do
    case $opt in
        a)
            echo "-a param: $OPTARG" >&2
            ;;
    esac
done

在编写此代码进行一些测试之后，我注意到每次我运行cchar -a "test"时，都必须在没有选项(cchar)的情况下运行它，否则，下一次我使用-a选项运行它时，它不会无法识别该选项.

After some testing while writing this, I've noticed everytime I run cchar -a "test", I have to run it without options (cchar) otherwise the next time I run it with the -a option, it doesn't recognise the option.

$ cchar

$ cchar -a "foo"
-a param: foo

$ cchar -a "foo"

$ cchar

$ cchar -a "foo"
-a param: foo

推荐答案

您必须重置变量OPTIND，该变量会跟踪当前的位置参数编号.使该变量在您的函数中本地化就足够了.

You have to reset the variable OPTIND, which keeps track of the current positional argument number. It should suffice to make that variable local to your function.

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