How to write crontab

CornTab:
  In terminal:
      -> crontab -e
      -> end of the file write

#35 20 * * * cd /home/zimpu; ./server
#0 * * * * cd && sh ./clearCache.sh
#0 16 * * * sudo apt-get update && sudo apt-get upgrade
#* * * * * cd /var/www/server/db/ && php insertData.php
#* * * * * cd /root/ && ./InterfaceKit-simple

6 Great Apps to View Disk Usage in Linux

1. If you are geeky enough, the easiest and fastest way is to use the ‘df’ command in your terminal. Simply type

df -h

2.

Baobab (Disk Usage Analyzer)

Most Linux distros with Gnome desktop (especially Ubuntu) use Baobab, also known as Disk Usage Analyzer, as the default disk usage viewer application. This is a great application that can break down and analyze your storage pattern to the last folder. You can define the folders that you want to scan and get it to return a circular rings chart representation of the space taken up by each files.

 3.

KDirStat and GdMap

If you have used WinDirStat on your Windows, you will agree that it is an useful application that can help you analyze and reclaim your disk space. What many people don’t know is that WinDirStat is actually a clone of the KDirStat. KDirStat has the same functionality as WinDirStat (or maybe the other way round), except that it is meant for the Linux desktop. While it is initially designed for KDE desktop, it is also compatible with any X11 desktop system.

KDirStat displays your folders/files in term of rectangular chunk. The biggest the filesize, the bigger is the chunk. This allows you to have a quick view of your filesystem and easily identify which folders/files is taking up a big chunk of space in the hard disk.

Gd Map is the KDirStat equivalent in Gnome desktop, except that it does not display the folder structure above the treemap and does not allows you to clean up the hard disk

4.

Filelight

Like Baobab, Filelight creates an interactive map of concentric, segmented rings that help visualize disk usage on your computer. You can easily zoom in to any folders by clicking on the respective segment on the rings.

5.

Philesight

Philesight is a Web-based implementation of Filelight and can be used on a remote server without graphical user interface. Philesight uses a command line program to generate the PNG files on your browser and a wrapper CGI script to allow navigating through the filesystem. One of its distinct feature is the colorful rainbow concentric rings that makes it pleasant to look at.

6.

xdiskusage

xdiskusage is a tiny program that displays your filesystem hierarchy from left to right with a rectangular shape of size respective to its file size. If you are scanning your Home folder, The left most rectangular box will represent the Home folder while the subsequent boxes to the right represent the next folders down the Home directory. You can easily zoom in/out of any folders (or rectangular box) by double-clicking on that box.

Fix Unknown device problem in android eclipse

0.
   open terminal: lsusb and get something like:
            Bus 003 Device 035: ID 19d2:1350 ZTE WCDMA Technologies MSM 
1.
Log in as root and create this file: /etc/udev/rules.d/51-android.rules.

Use this format to add each vendor to the file:
SUBSYSTEM=="usb", ATTR{idVendor}=="0bb4", MODE="0666", GROUP="plugdev" 

2

Now execute: chmod a+r /etc/udev/rules.d/51-android.rules

3. Device list code:

     device list code

Format time as string

strftime

size_t strftime (char* ptr, size_t maxsize, const char* format,
                 const struct tm* timeptr );

Format time as string

Copies into ptr the content of format, expanding its format specifiers into the corresponding values that represent the time described intimeptr, with a limit of maxsize characters.

Parameters

ptr

Pointer to the destination array where the resulting C string is copied.

maxsize

Maximum number of characters to be copied to ptr, including the terminating null-character.

format

C string containing any combination of regular characters and special format specifiers. These format specifiers are replaced by the function to the corresponding values to represent the time specified in timeptr. They all begin with a percentage (%) sign, and are:

specifier	Replaced by	Example
%a	Abbreviated weekday name *	Thu
%A	Full weekday name *	Thursday
%b	Abbreviated month name *	Aug
%B	Full month name *	August
%c	Date and time representation *	Thu Aug 23 14:55:02 2001
%C	Year divided by 100 and truncated to integer (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	Short MM/DD/YY date, equivalent to %m/%d/%y	08/23/01
%e	Day of the month, space-padded ( 1-31)	23
%F	Short YYYY-MM-DD date, equivalent to %Y-%m-%d	2001-08-23
%g	Week-based year, last two digits (00-99)	01
%G	Week-based year	2001
%h	Abbreviated month name * (same as %b)	Aug
%H	Hour in 24h format (00-23)	14
%I	Hour in 12h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	New-line character ('\n')
%p	AM or PM designation	PM
%r	12-hour clock time *	02:55:02 pm
%R	24-hour HH:MM time, equivalent to %H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal-tab character ('\t')
%T	ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S	14:55:02
%u	ISO 8601 weekday as number with Monday as 1 (1-7)	4
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%V	ISO 8601 week number (00-53)	34
%w	Weekday as a decimal number with Sunday as 0 (0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%x	Date representation *	08/23/01
%X	Time representation *	14:55:02
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%z	ISO 8601 offset from UTC in timezone (1 minute=1, 1 hour=100) If timezone cannot be termined, no characters	+100
%Z	Timezone name or abbreviation * If timezone cannot be termined, no characters	CDT
%%	A % sign	%

* The specifiers marked with an asterisk (*) are locale-dependent.
Note: Yellow rows indicate specifiers and sub-specifiers introduced by C99. Since C99, two locale-specific modifiers can also be inserted between the percentage sign (%) and the specifier proper to request an alternative format, where applicable:

Modifier	Meaning	Applies to
E	Uses the locale's alternative representation	%Ec %EC %Ex %EX %Ey %EY
O	Uses the locale's alternative numeric symbols	%Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy

timeptr

Pointer to a tm structure that contains a calendar time broken down into its components (see struct tm).

Return Value

If the length of the resulting C string, including the terminating null-character, doesn't exceed maxsize, the function returns the total number of characters copied to ptr (not including the terminating null-character).
Otherwise, it returns zero, and the contents of the array pointed by ptr are indeterminate.

Compatibility

Particular library implementations may support additional specifiers or combinations.
Those listed here are supported by the latest C and C++ standards (both published in 2011), but those in yellow were introduced in C99 (only required for C++ implementations since C++11), and may not be supported by libraries that comply with older standards.

Example

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

/* strftime example */ #include <stdio.h> /* puts */ #include <time.h> /* time_t, struct tm, time, localtime, strftime */ int main () { time_t rawtime; struct tm * timeinfo; char buffer [80]; time (&rawtime); timeinfo = localtime (&rawtime); strftime (buffer,80,"Now it's %I:%M%p.",timeinfo); puts (buffer); return 0; }

Example output:

Now it's 03:21PM.

How to convert char to string

Char to string:

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#include <sstream> #include <string> stringstream ss; string s; char c = 'a'; ss << c; ss >> s;

String to int:

1 2 3 4 5 6 7

#include <sstream> #include <string> stringstream ss; string s; int n = 1; ss << n; ss >> s;

Setup MySQL C Access

Installing The MySQL C libraries

MySQL comes with C-libraries:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install libmysqlclient-dev

#include <sys/time.h>
#include <mysql.h>
#include <iostream>
using namespace std;

MYSQL *connection,mysql;
MYSQL_RES *result;
MYSQL_ROW row;
int query_state;

int main()
{
 mysql_init(&mysql);
 connection = mysql_real_connect(&mysql,"hostName","userName","password","dbName",0,0,0);
 if(connection==NULL)
 {
  cout<<mysql_error(&mysql)<<endl;
 }
 else
 {
  cout<<"CONNECTED!"<<endl;
 }

if (mysql_query(connection, "INSERT INTO envTemperature VALUES('','2','60','2014-02-08','17:12:01')")) {
      cout<<"\n not success!\n";
  }
  mysql_close(connection);
 return 0;
}

Save it in a directory on the RPI, then on the command line go to that directory and use this to compile it:

g++ main.c `mysql_config --cflags` `mysql_config --libs`

Resetting forgotten phpmyadmin password

Simply change or reset your MySQL root password by doing the following:

1. Stop the MySQL server
   sudo service mysql stop
2. Start mysqld
   sudo mysqld --skip-grant-tables &
3. Login to MySQL as root
   mysql -u root mysql
4. Change MYSECRET with your new root password
   UPDATE user SET Password=PASSWORD('MYSECRET') WHERE User='root'; FLUSH PRIVILEGES; exit;
5. Kill mysqld
   sudo pkill mysqld
6. Start mysql
   sudo service mysql start
7. Login to phpmyadmin as root with your new password