BASH:具有默认参数值的getopts [英] BASH: getopts with default parameters value

问题描述

我还有另一个bash脚本问题，我根本无法解决.这是我显示问题的简化脚本:

I've got another bash-script problem I simply couldn't solve. It's my simplified script showing the problem:

while getopts "r:" opt; do
case $opt in

  r)
    fold=/dev
    dir=${2:-fold}

     a=`find $dir -type b | wc -l`
     echo "$a"
  ;;
esac
done

我通过以下方式致电

  ./sc.sh -r /bin

这是可行的，但是当我不提供参数时，它是无效的:

and it's work, but when I don't give a parameter it doesn't work:

  ./sc.sh -r

在此脚本中，我希望/dev为我的默认参数$ 2.

I want /dev to be my default parameter $2 in this script.

推荐答案

之前可能还有其他参数，请不要对参数号($ 2)进行硬编码.

There may be other parameters before, don't hard-code the parameter number ($2).

getopts帮助说

The getopts help says

当一个选项需要一个参数，getopts的地方这样的说法到壳体变量OPTARG.结果 ...
[在静默错误报告模式下，如果 找不到必需的参数，getopts在名称中放置一个:"，然后 将OPTARG设置为找到的选项字符.

When an option requires an argument, getopts places that argument into the shell variable OPTARG.
...
[In silent error reporting mode,] if a required argument is not found, getopts places a ':' into NAME and sets OPTARG to the option character found.

所以你想要

dir=/dev                            # the default value
while getopts ":r:" opt; do         # note the leading colon
    case $opt in
        r) dir=${OPTARG} ;;
        :) if [[ $OPTARG == "r" ]]; then
               # -r with required argument missing.
               # we already have a default "dir" value, so ignore this error
               :
           fi
           ;;
    esac
done
shift $((OPTIND-1))

a=$(find "$dir" -type b | wc -l)
echo "$a"

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