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Difference between 3NF and BCNF in simple terms (must be able to explain to an 8-year old)
...quivalent to Codd's:
A relation, R, is in 3NF iff for every nontrivial FD (X->A) satisfied
by R at least ONE of the following conditions is true:
(a) X is a superkey for R, or
(b) A is a key attribute for R
BCNF requires (a) but doesn't treat (b) as a special case of its own. In...
UDP vs TCP, how much faster is it? [closed]
...do care about latencies A LOT; it is this simple thing which accounts for 99% of legit uses for UDP. And a few nitpicks: (a) group delivery DOES NOT work over the Internet (and unlikely ever will), so it is the Intranet-only realm; (b) per Google, only 8-9% of Internet population has problems with ...
How to detect if a script is being sourced
...ocess $$ is $v ($0, $BASH_SOURCE)" ')
process 29301 is sourced (bash, /dev/fd/63)
bash <(echo $'#!/bin/bash
[ "$0" = "$BASH_SOURCE" ] && v=own || v=sourced;
echo "process $$ is $v ($0, $BASH_SOURCE)" ')
process 16229 is own (/dev/fd/63, /dev/fd/63)
I use source in...
Disable autocomplete via CSS
...n CSS. However, html has an easy code for this:
<input type="text" id="foo" value="bar" autocomplete="off" />
If you're looking for a site-wide effector, an easy one would be to simply have a js function to run through all 'input' s and add this tag, or look for the corresponding css class ...
Get first and last date of current month with JavaScript or jQuery [duplicate]
...
I fixed it with Datejs
This is alerting the first day:
var fd = Date.today().clearTime().moveToFirstDayOfMonth();
var firstday = fd.toString("MM/dd/yyyy");
alert(firstday);
This is for the last day:
var ld = Date.today().clearTime().moveToLastDayOfMonth();
var lastday = ld.toStrin...
[解决]CTRL: PTY read or GRE write failed - 更多技术 - 清泛网 - 专注C/C++及内核技术
...查看系统日志[cat var log messages |grep pptpd]后发现）GRE: read(fd=6,buffer=80504c0...pptp vpn服务器连接失败出现以下日志内容：
（查看系统日志[ cat /var/log/messages |grep pptpd ]后发现）
GRE: read(fd=6,buffer=80504c0,len=8196) from PTY failed: status = -1 er...
Google breakpad stackwalker无法加载符号 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...head -n1 tmp/c++11.sym
#todo:
mkdir -p ./symbols/c++11/6EDC6ACDB282125843FD59DA9C81BD830
mv tmp/c++11.sym ./symbols/c++11/6EDC6ACDB282125843FD59DA9C81BD830
rm -rf tmp
路径有要求，GUID来自 .so 文件的头部。
为了方便，写个 python 脚本 gen_symbols.py 自动生成：
#...
/proc 内核统计信息各文件的含义 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...的统计文件，如下： ls -F proc 904 attr coredump_filter fdinfo make-it-fail mountstats oom_score_adj sched stat 1、各进程的统计文件，如下：
# ls -F /proc/904/
attr/ coredump_filter fdinfo/ make-it-fail mountstats oom_score_adj sched st...
How to validate an Email in PHP?
...x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}@)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\...
What's the best way to check if a file exists in C?
...itions, then use this:
#include <fcntl.h>
#include <errno.h>
fd = open(pathname, O_CREAT | O_WRONLY | O_EXCL, S_IRUSR | S_IWUSR);
if (fd < 0) {
/* failure */
if (errno == EEXIST) {
/* the file already existed */
...
}
} else {
/* now you can use the file */
}
...