关于sed匹配JSON数据中的数字问题

{"list":[{"fs_id":4176732013,"path":"\/apps\/zjhui\/bash","ctime":1389845838,"mtime":1389845838,"block_list":"[\"286dc423e71186936c39e3507d2d0cf1\"]","size":2076,"isdir":0,"ifhassubdir":0,"filenum":0}],"request_id":2785468470}

有这么一串，我想利用sed将"isdir":0这里的0单独取出来。利用如下命令:
sed -n 's/"isdir":\(.*\)/\1/p'
发现匹配出来的是:

{"list":[{"fs_id":4176732013,"path":"\/apps\/zjhui\/bash","ctime":1389845838,"mtime":1389845838,"block_list":"[\"286dc423e71186936c39e3507d2d0cf1\"]","size":2076,0,"ifhassubdir":0,"filenum":0}],"request_id":2785468470}

isdir没了。而我想要的是isdir后面那个0（这个数字也有可能是1）
求解！