查看方法：ulimit -a 软限制
下面是Ubuntu12.04 x64系统下，进程资源限制情况：
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 63315 信号可以被挂起的最大数
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1024 内核可以同时打开的文件描述符的最大值
pipe size (512 bytes, -p) 8 管道最大使用的空间为 4K
POSIX message queues (bytes, -q) 819200 消息队列最大使用的内存 800K
real-time priority (-r) 0
stack size (kbytes, -s) 8192 进程栈区最大为8M
cpu time (seconds, -t) unlimited
max user processes (-u) 63315 用户最大可以启动进程数
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
ulimit -a -H 硬限制
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 63315
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 4096
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) unlimited
cpu time (seconds, -t) unlimited
max user processes (-u) 63315
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited