获取Linux进程资源使用情况（cpu，磁盘，网络）

I want to use the /proc to find the resource usage of a particular process every second. The resources include cputime, disk usage and network usage. I looked at /proc/pid/stat , but I am not sure whether I am getting the required details. I want all 3 resource usage and I want to monitor them every second.I want to use the /proc to find the resource us