how to send email from terminal in ubuntu

Follow this article to setup.
while you should use application password as your password in ~/.msmtprc.
You can generate application password from here .

Use Java and Python to write a small tool

 I wrote a tool to parse fail result files of some integration tests. I wrote it in Java and in Python, it turns out using Python is far more easy to write and to read. Bellowing are some comparisons.

 What I want to do:

1. Read all txt files in a given folder.
2. Check if every txt files contains a specific string
3. Parse some information from those files which doesn't contains the specific string.

=========================================================

 Firstly, find all *.txt in a given folder.

• In Java 7: 

      final Pattern p = Pattern.compile("(.*).txt");
      File[] files = this.listFiles(new FileFilter() {
        @Override      public boolean accept(File file) {
          return p.matcher(file.getName()).matches();
        }
      });
  

  
  
• In Python 2: 
  

  files = [ f for f in os.listdir(folder_path) if re.match('(.*).txt',f)]

My comments: There are so many verbose code to create a filter to filter file name in Java 7. All I want to do is to type *.txt somewhere and just give me all txt files in the folder. Every code other than the filter (*.txt) are redundant except specifying the folder. 

=========================================================         

Next, check if a file contains the string "Failures: 0, Errors: 0, Skipped: 0"

• In Java 7:  I copy some codes from http://stackoverflow.com/questions/5600422/method-to-find-string-inside-of-the-text-file-then-getting-the-following-lines, so my method looks like this:
  

  public boolean containsText(String keyword){
    File file = new File(this.getPath());
    try {
      Scanner scanner = new Scanner(file);
      //now read the file line by line...
      while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        if(line.contains(keyword)) {
          return true;
        }
      }
    } catch(FileNotFoundException e) {
      //handle this  }
    return false;
  }

• In Python 2:  I copy codes from http://stackoverflow.com/questions/4940032/search-for-string-in-txt-file-python, so my code looks like this:    

  if not 'Failures: 0, Errors: 0, Skipped: 0' in open(folder_path+'/'+file).read():
       // do something

My comments: To check if a file contains a specific string, either we check it line by line or we read all text in the file into a string and check if the string contains the target. I really don't care which way I use since the file size is not too big. Python just tells what I want to do in one line. Actually I hope I can type "if not "xxx" in File(path)" to make my code more describable. 

=========================================================
 Last step, for each file which doesn't contains "Failures: 0, Errors: 0, Skipped: 0", extract all fail test names. Lines contains a fail test name looks like: "testSetStationOnOff(com.live365.api.station.integration.StationTestIT)  Time elapsed: 0.066 sec  <<< FAILURE!", so the format is "[test name]([test class name]) Time elapsed: [seconds] sec <<< FAILURE!", and I just want to extract the [test name] part.

• In Java 7:     

  //print fail test names  Scanner scanner = new Scanner(report);
  while (scanner.hasNextLine()) {
    String line = scanner.nextLine();

    Pattern pattern = Pattern.compile("(.*)\\((.*)\\)  Time elapsed: (.*) sec  <<< FAILURE!");
    if(pattern.matcher(line).matches()){
      Matcher matcher = pattern.matcher(line);
      matcher.find();
      println("\t"+matcher.group(1));
    }
  }

• In Python 2:

  #print fail test nameslines = open(report).read();
  results = re.findall('(.*)\((.*)\)  Time elapsed: (.*) sec  <<< FAILURE!',lines)
  for result in results:
      print '\t'+result[0]

My comments:  Yes, what I want to do is to find all strings matches the format! Again in Python my purpose is so obviously shown in two line, but in Java I have to write so many details which I really don't care about. For example, Pattern.compile(...). Why can't I just type line.matches("xxx") and Java handles the rest for me?

Timeout and retry in shell script

最近工作上需要寫一個script每隔10分鐘就重複做A,B,C三件事情,但是有一個問題,A在正常情況下30秒內做完了,但是一旦出問題, 就會一直停在那邊,所以常常等我心血來潮來看看它跑得怎麼樣了的時候,就發現他已經卡在A步驟好幾個小時了. 所以我需要Timeout function! 而且最好再來個retry機制.

timeout很簡單,只要搜尋 "linux timeout" , "linux command timeout" ...等等,馬上就會用了.

timeout 2s ping 127.0.0.1

那retry呢? retry就用一個for loop,重複做n次,如果n次以內有執行成功就break,否則就做到n次為止, 完整的 shell script範例如下:

========================================

#! /bin/bash

RETRY_LIMIT=3
TIME_OUT=3
count=0
for (( n=0; n<$RETRY_LIMIT; n++));
do
  count=$(($count+1))
  printf "run do_something $count times\n\n"
  timeout $TIME_OUT ./do_something.sh
  status=$?
  printf "\n"
  if [ $status -eq 0 ]; then
    echo "break for loop"
    exit 0
  fi
done
exit 1

=======================================

ps. do_something.sh 是一個為了測試這個timeout and retry寫的script,

他會隨機的sleep 1到6秒,script如下:

=======================================

#!/bin/bash
echo "start running do_something()"
num=$[$RANDOM%6+1]
echo "sleep $num seconds"
sleep $num
echo "end of do_something()"

=======================================

自製Arduino

 之前做了一個舉牌機器人的project, 使用我的Arduino去控制伺服馬達. 當我做完後,面臨到一個問題: Arduino很貴啊,我不把它拆下來,就不能拿它繼續玩其他project了,但是我不希望拆掉我的舉牌機器人啊. 於是我用之前研究的自製arduino來代替我買的Arduino,如下圖.

具體作法可以參考

在麵包板上建構Arduino（ATmega328P加USB轉TTL Serial轉接卡）

成本總共大約 200左右:

麵包板 68元 (在良興買的)
ATMEGA328P-PU 52元  (在露天拍賣買的)
按鍵開關 1.5*2=3元 (在露天拍賣買的)
usb to uart 轉板 68元 (在露天拍賣買的)
石英振盪器 3元 (在露天拍賣買的)
電阻電容  沒算,一定小於10元 (在台北車站地下街的電子材料行買的)

心得:

1. 最花時間的是把材料買齊
2. USB to UART 轉板價錢差異很大,因為我想知道極限在哪,所以故意買最便宜的,實際上拿來用也還沒出什麼問題
3. 線路還蠻簡單的,照著葉難網誌上的圖一下子就接好了.
4. 燒錄時在IDE上按下download以後,要趕快按麵包板上的按鈕,才會開始燒錄,不然會燒錄失敗. 燒錄失敗就再試一次就好了,多試幾次就會了. 每次要燒錄都要按按鈕有點麻煩,建議開發還是用正常的Arduino板子,等到想要把project保存下來再轉移成這種方式.