#!/bin/bash

if [ $# -eq 1 ];then
    ls ${1}
else
    if [ $# -eq 2 ];then
        if [ $1 == "-l" ];then
            ls -l ${2}
        else
            echo "invalid pararmeter."
            exit -1
        fi
    else
        echo "input error."
        exit -1
    fi
fi

------解决方案--------------------

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Python code
#!/bin/bash

if [ $# -eq 1 ];then
    ls ${1}
else
    if [ $# -eq 2 ];then
        if [ $1 == "-l" ];then
            ls -l ${2}
        else
            echo "invalid pararmeter."
    ……