linux and human.

[bug] x200 has 48 hours battery life

如何檢視Linux系統distribution版本

cat /etc/*release
cat /etc/issue

[Ruby] string format

"%.3f" % (1.0/7) # "0.143"
"%5.1f" % 345.6789 # "345.7"

"%05d" % 123 # "00123"
"%-5s" % "ID" # "ID "
"%04x" % 0xfc14 # "fc14"

"%6.2f, %05d" % [345.6789,123] # "345.68, 00123"
"%-5s: %04x" % ["ID", 0xfc14] # "ID : fc14"

vi 復原跟做

in command mode, use u key to undo and Ctr-r key to redo.

[FUN]chrome 可以開幾個tab 呢?

a lot of tabs.

[指令] WC - 印出文件 行數 字數 byte數

指令： wc

參數：

-c, --bytes               印出位元數

-m, --chars              印出字數 印出該文件有幾個字

-l, --lines                 印出該文件有幾行   

-L, --max-line-length 印出該文件最長的那行有幾字

-w, --words              印出單字數目

This is just a note to prevent me forgot it. :P

[問題] switch 裡面放switch 時 default: 的問題

error: ‘default’ label in scope of identifier with variably modified type not containing enclosing switch statement

to be solved...

解決在OS X 使用terminal遠端使用screen無法backspace的情況

In terminal program, choose preferences -> advanced;

select "Delete sends Ctrl+H"

done!

About unistd.h

在unix-like的系統內, unistd.h所定義的介面大多由一些system call的函式所組成, 像是fork, pipe 以及一需 基本IO

(read, write, open, close) 等等

malloc vs new

Difference between uses of new/malloc & delete/free:

(a) Operator new constructs an object (calls constructor of object), malloc does not.
(b) Operator new is an operator, malloc is a function.
© Operator new can be overloaded, malloc cannot be overloaded.
(d) Operator new throws an exception if there is not enough memory, malloc returns a NULL.
(e) Operator new[] requires to specify the number of objects to allocate, malloc requires to specify the total number of bytes to allocate.
(f) malloc() returns void *, which has to be explicitly cast to the desired type but new returns the proper type.
(g) Operator new/new[] must be matched with operator delete/delete[] to deallocate memory, malloc() must be matched with free() to deallocate memory.
(h) The new/delete couple does not have a realloc alternative that is available when malloc/free pair is used. realloc is used to resize the length of an array or a memory block dynamically.

reference:http://c.ittoolbox.com/groups/technical-functional/cpp-l/malloc-vs-new-1255507

codeploy? It's hard to use it

Recently, I tried to use codeploy to upload my program to many planetlab nodes.

But seeing the setting instruction, it's too inconvenient.

There are too many parameter to set.

So I write a simple ruby script to implement this multiple upload function.

usage: ./multi-upload directly_you_want_to_upload

script:

#! /usr/bin/ruby

arr = IO.readlines("node_list")

arr.each { |x|

puts "node name:#{x.chomp}"

cmd = "scp -r #{ARGV[0]} ACCOUNT@#{x.chomp}:/home/ACCOUNT"

puts `#{cmd}`

}

See, 9 lines code can do the same thing.

Why don't use it?

vim window tips

#define c-w Control + key W

對目前編輯檔案分割視窗:
分割垂直視窗: c-w v
分割水平視窗: c-w s
關閉視窗: c-w q
留下目前視窗並且關閉其他視窗: c-w o
於分割視窗開新檔案: c-w n

切換:
切換到下方視窗: c-w j
切換到上方視窗: c-w k
切換到左方視窗: c-w h
切換到右方視窗: c-w l
切換到下一個視窗:
調整大小
調整視窗垂直大小: c-w [+|-]
調整視窗水平大小: c-w [<|>]

how many terminals can terminator open

如何讓freeBSD開機就自動執行某個程式

很簡單, 寫個程式然後丟到/usr/local/etc/rc.d即可

simulation vs experiment

這幾天研究遇到一個問題: 實驗和模擬跑出來的結果有個差別, 於是我就先畫出圖來比較, 重點就是我發現我跑decoder的程式是模擬用的程式, 而模擬的程式就是會故意把幾個voice frame拿掉, 於是我decode的時候, 拿實驗收到的frame file餵給他, 他可能就把它當成原始的voice frame, 然後在decode出可以聽的音效wav檔. 主要會發現的原因是我已經知道模擬的時候是把一些frame label起來 指定那些就是要loss的, 但是沒有想到這件事是在decode的時候做. 而我又把decoder模擬程式當成單純decode功能的程式, 如何證明說decoder參數設定會影響輸出wav的結果呢, 第一 看到模擬跑的script裡面只有出現decoder才會用的參數, 第二 實際用同樣的bit檔 去測試但是使用不同的模擬參數, 果然跑出來的wav效果不一樣. 目前先不管模擬loss, burst有沒有算對, 先把decode程式改成單純decode不吃任何參數. 在比較模擬與實驗的結果差異.

Install mac fonts notes

1. put the font in /usr/share/fonts/fonddocument

2. # fc-cache -f -v

FreeBSD is looking at you.

忘記root密碼 步驟

1. push "e"

2. push "e" on kernel option.

3. input "single"

4. push "b" on kernel option.

5. #passwd root

6. reboot

X server not reponding

今天嘗試連到gateway然後再連到其他機器, 但是想要用ssh -X ip 的時候, 圖形好像傳不回來,並且出現下列訊息

Xlib: connection to "localhost:10.0" refused by server Xlib: PuTTY X11 proxy: MIT-MAGIC-COOKIE-1 data did not match Error: Can't open display: localhost:10

目前不知道原因,正在研究中.

p.s. 如果用ssh -Y ip 就好了.