判断输入字符是否合法(只有字符或数字)

#/bin/sh

validAlphaNum()
{
    compressed="$(echo $1 | sed -e 's/[^[:alnum:]]//g')"

    if [ $compressed == $1 ]
    then
        return 0
    else
        return 1
    fi
}

echo -n "Enter input:"
read input

if ! validAlphaNum "$input"
then
    echo "Your input must consist only alpha and number" >&2
    exit 1
else
    echo "Input is valid"
fi

exit 0