imet

Linux pstree shows running processes as a tree. The tree is rooted at either pid or init if pid is omitted. If a user name is specified, all process trees rooted at processes owned by that user are shown.
Install pstree

#On Mac OS
brew install pstree
 
#On Fedora/Red Hat/CentOS
yum install psmisc #using psmisc package for pstree
 
#On Ubuntu/Debian APT

imet

正则匹配

匹配中文字符的正则表达式： [\u4e00-\u9fa5] 
评注：匹配中文还真是个头疼的事，有了这个表达式就好办了 

匹配双字节字符(包括汉字在内)：[^\x00-\xff] 
评注：可以用来计算字符串的长度（一个双字节字符长度计2，ASCII字符计1） 

匹配空白行的正则表达式：\n\s*\r 
评注：可以用来删除空白行 

imet

/**
 * Copyright (c) 2011 Red Hat, Inc.
 *
 * This software is licensed to you under the GNU General Public License,
 * version 2 (GPLv2). There is NO WARRANTY for this software, express or
 * implied, including the implied warranties of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. You should have received a copy of GPLv2
 * along with this software; if not, see
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
 *

imet

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs