shell 判断一个字符串是否由字母数字组成

摘自：http://blog.51cto.com/lynnteng0/804520

describe="it's a describe by yourself"
 
if echo "$describe" | grep -q '^[a-zA-Z0-9]\+$'; then
    echo "ok"
else
    echo "invalid"
fi

　　

describe="it's a describe by yourself"
 
if echo "$describe" | grep -q '[^a-zA-Z0-9]'; then
echo "invalid"
fi