Install sqlite3 library in Gumstix for Qt application

My Qt program will create a database by using sqlite3 plugin app.
The program is working happily in ubuntu, meanwhile, i can use command line to do all sqlite3 command in gumstix. but i got error message when i run it in gumstix.

the error message shows on my touch screen as:

"Unable to open database, An error occurred while opening the connection."

take a look my program:

// create new database
QDate sDate = QDate::currentDate();
QString dbName;
dbName = QString(QApplication::applicationDirPath()).append("/database/I-" + sDate.toString("MMyyyy") + ".db");
mydb = QSqlDatabase::addDatabase("QSQLITE");

if (!QFile::exists(dbName))
QSqlQuery query;
query.exec("create table c1Params (ID int primary key unique, "
"Time QString, Status int, Spare QByteArray)");


if (!
QMessageBox::warning(this, tr("Unable to open database"), tr("An error occurred while "
"opening the connection: ") + m4db.lastError().text());

This indicate that 'mydb' has not been able to created.
The following message is shown in on gumstix prompt.

root@overo:~# ./mypro -qws
Trying to open File
Opened File succesfully
QSqlDatabase: QSQLITE driver not loaded
QSqlDatabase: available drivers:
QSqlQuery::exec: database not open
QSqlQuery::exec: database not open
Segmentation fault

used 'strace' command to track the error message, and compare stack content between ubuntu and gumstix.

in my ubuntu:
$ strace -o /home/czhang/Desktop/test  ./mypro

stat("/etc/xdg/Trolltech.conf", 0x7fff4c33bec0) = -1 ENOENT (No such file or directory)
stat("/etc/xdg/Trolltech.conf", 0xec71c8) = -1 ENOENT (No such file or directory)
stat("/usr/lib/kde4/plugins/sqldrivers/.", 0xec7348) = -1 ENOENT (No such file or directory)
lstat("/usr/lib/kde4/plugins/sqldrivers/.", 0x7fff4c33c2a0) = -1 ENOENT (No such file or directory)
stat("/usr/lib/qt4/plugins/sqldrivers/.", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/usr/lib/qt4/plugins/sqldrivers", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 22
statfs("/usr/lib/qt4/plugins/sqldrivers", {f_type="EXT2_SUPER_MAGIC", f_bsize=4096, f_blocks=9612197, f_bfree=7908029, f_bavail=7419748, f_files=2444624, f_ffree=2135156, f_fsid={490287925, 258803822}, f_namelen=255, f_frsize=4096}) = 0
getdents(22, /* 4 entries */, 32768)    = 128
stat("/usr/lib/qt4/plugins/sqldrivers/", {st_mode=S_IFREG|0644, st_size=73432, ...}) = 0
in gumstix:
$ strace -o /home/root/test  ./mypro

stat64("/etc/xdg/Trolltech.conf", 0xbe916208) = -1 ENOENT (No such file or directory)
stat64("/etc/xdg/Trolltech.conf", 0x205ad0) = -1 ENOENT (No such file or directory)
stat64("/home/root/sqldrivers/.", 0x1ef1b8) = -1 ENOENT (No such file or directory)
lstat64("/home/root/sqldrivers/.", 0xbe916400) = -1 ENOENT (No such file or directory)
write(2, "QSqlDatabase: QSQLITE driver not"..., 40) = 40
write(2, "QSqlDatabase: available drivers:"..., 34) = 34

here is the problem. the Qt in gumstix can not locate the sqlite library interface at directory /home/root/sqldrivers.

"The Qt plugins should be deployed in one of the locations that Qt looks when it needs a plugin: look for Deploying Plugins in Assistant. In the case of the Qsqlite driver you could deploy it in a sub directory "sqldrivers" of the directory containing the program executable or in a plugins/sqldrivers directory of central Qt installation. Similar locations exist for other plugin types."

ok, create a dirctory in gumstix
$ mkdir /home/root/sqldrivers
$ scp czhang@x.x.x.x:/build/czhang/qt-everywhere-opensource-src-4.7.0/plugins/sqldrivers/ .



Qt display ° (temperature degree) character in Linux

In my Qt program, I would like to display ° character for temperature.
For example:
QLabel *tempLabel = new QLabel("37°C");

Although the ° character will ouput correctly on Windows, it gives strange things instead on Linux.

This is what I found from Qt forum:
"QString by default assumes a conversion from C Strings using a local 8 bit encoding which is different for different systems. Therefore what works on Windows will not work on Linux. You need to explicitely set what encoding should be used either by QTextCodec::setCodecForCStrings() or by explicitely saying which codec to use for a particular conversion, for instance QString::fromUtf8()."

Here is my new code:
QLabel *tempLabel = new QLabel("37" + QString::fromUtf8("°") + "C");


Basic vi Commands in Linux

What is vi?

The default editor that comes with the UNIX operating system is called vi (visual editor). [Alternate editors for UNIX environments include pico and emacs, a product of GNU.]
The UNIX vi editor is a full screen editor and has two modes of operation:
  1. Command mode commands which cause action to be taken on the file, and
  2. Insert mode in which entered text is inserted into the file.
In the command mode, every character typed is a command that does something to the text file being edited; a character typed in the command mode may even cause the vi editor to enter the insert mode. In the insert mode, every character typed is added to the text in the file; pressing the (Escape) key turns off the Insert mode.
While there are a number of vi commands, just a handful of these is usually sufficient for beginning vi users. To assist such users, this Web page contains a sampling of basic vi commands. The most basic and useful commands are marked with an asterisk (* or star) in the tables below. With practice, these commands should become automatic.
NOTE: Both UNIX and vi are case-sensitive. Be sure not to use a capital letter in place of a lowercase letter; the results will not be what you expect.

To Get Into and Out Of vi

To Start vi

To use vi on a file, type in vi filename. If the file named filename exists, then the first page (or screen) of the file will be displayed; if the file does not exist, then an empty file and screen are created into which you may enter text.

* vi filename edit filename starting at line 1
  vi -r filename recover filename that was being edited when system crashed

To Exit vi

Usually the new or modified file is saved when you leave vi. However, it is also possible to quit vi without saving the file.
Note: The cursor moves to bottom of screen whenever a colon (:) is typed. This type of command is completed by hitting the (or ) key.

* :x quit vi, writing out modified file to file named in original invocation
  :wq quit vi, writing out modified file to file named in original invocation
  :q quit (or exit) vi
* :q! quit vi even though latest changes have not been saved for this vi call

Moving the Cursor

Unlike many of the PC and MacIntosh editors, the mouse does not move the cursor within the vi editor screen (or window). You must use the the key commands listed below. On some UNIX platforms, the arrow keys may be used as well; however, since vi was designed with the Qwerty keyboard (containing no arrow keys) in mind, the arrow keys sometimes produce strange effects in vi and should be avoided.
If you go back and forth between a PC environment and a UNIX environment, you may find that this dissimilarity in methods for cursor movement is the most frustrating difference between the two.
In the table below, the symbol ^ before a letter means that the key should be held down while the letter key is pressed.

* j or
  [or down-arrow]
move cursor down one line
* k [or up-arrow] move cursor up one line
* h or
  [or left-arrow]
move cursor left one character
* l or
  [or right-arrow]
move cursor right one character
* 0 (zero) move cursor to start of current line (the one with the cursor)
* $ move cursor to end of current line
  w move cursor to beginning of next word
  b move cursor back to beginning of preceding word
  :0 or 1G move cursor to first line in file
  :n or nG move cursor to line n
  :$ or G move cursor to last line in file

Screen Manipulation

The following commands allow the vi editor screen (or window) to move up or down several lines and to be refreshed.

  ^f move forward one screen
  ^b move backward one screen
  ^d move down (forward) one half screen
  ^u move up (back) one half screen
  ^l redraws the screen
  ^r redraws the screen, removing deleted lines

Adding, Changing, and Deleting Text

Unlike PC editors, you cannot replace or delete text by highlighting it with the mouse. Instead use the commands in the following tables.
Perhaps the most important command is the one that allows you to back up and undo your last action. Unfortunately, this command acts like a toggle, undoing and redoing your most recent action. You cannot go back more than one step.

* u UNDO WHATEVER YOU JUST DID; a simple toggle

The main purpose of an editor is to create, add, or modify text for a file.

Inserting or Adding Text

The following commands allow you to insert and add text. Each of these commands puts the vi editor into insert mode; thus, the key must be pressed to terminate the entry of text and to put the vi editor back into command mode.
* i insert text before cursor, until hit
  I insert text at beginning of current line, until hit
* a append text after cursor, until hit
  A append text to end of current line, until hit
* o open and put text in a new line below current line, until hit
* O open and put text in a new line above current line, until hit

Changing Text

The following commands allow you to modify text.
* r replace single character under cursor (no needed)
  R replace characters, starting with current cursor position, until hit
  cw change the current word with new text,
starting with the character under cursor, until hit
  cNw change N words beginning with character under cursor, until hit;
  e.g., c5w changes 5 words
  C change (replace) the characters in the current line, until hit
  cc change (replace) the entire current line, stopping when is hit
  Ncc or cNc change (replace) the next N lines, starting with the current line,
stopping when is hit

Deleting Text

The following commands allow you to delete text.
* x delete single character under cursor
  Nx delete N characters, starting with character under cursor
  dw delete the single word beginning with character under cursor
  dNw delete N words beginning with character under cursor;
  e.g., d5w deletes 5 words
  D delete the remainder of the line, starting with current cursor position
* dd delete entire current line
  Ndd or dNd delete N lines, beginning with the current line;
  e.g., 5dd deletes 5 lines

Cutting and Pasting Text

The following commands allow you to copy and paste text.
  yy copy (yank, cut) the current line into the buffer
  Nyy or yNy copy (yank, cut) the next N lines, including the current line, into the buffer
  p put (paste) the line(s) in the buffer into the text after the current line

Other Commands

Searching Text

A common occurrence in text editing is to replace one word or phase by another. To locate instances of particular sets of characters (or strings), use the following commands.
  /string search forward for occurrence of string in text
  ?string search backward for occurrence of string in text
  n move to next occurrence of search string
  N move to next occurrence of search string in opposite direction

Determining Line Numbers

Being able to determine the line number of the current line or the total number of lines in the file being edited is sometimes useful.
  :.= returns line number of current line at bottom of screen
  := returns the total number of lines at bottom of screen
  ^g provides the current line number, along with the total number of lines,
in the file at the bottom of the screen

Saving and Reading Files

These commands permit you to input and output files other than the named file with which you are currently working.

  :r filename read file named filename and insert after current line
(the line with cursor)
  :w write current contents to file named in original vi call
  :w newfile write current contents to a new file named newfile
  :12,35w smallfile write the contents of the lines numbered 12 through 35 to a new file named smallfile
  :w! prevfile write current contents over a pre-existing file named prevfile