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Editing: odbcinst.html

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<title>unixODBC without the GUI</title>
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<h1><center>unixODBC without the GUI</center></h1>
<h3><center>Or<br>
everything you wanted to know about odbcinst but were afraid to ask</center></h3>
<h3>Purpose</h3>
A lot of people are using unixODBC but for a number of reasons are not building
the GUI configuration and testing tools (ODBCConfig and DataManager). This
document is aimed at these people and hopes to explain what you need to do
and when to do it.
<br>

ODBC first appeared within Windows 3.0. At this time Windows used .ini files
to contain configuration information. These are text files containing the 
following layout
<pre>[section1]
entry1 = value
entry2 = value

[section2]
entry1 = value
entry2 = value
...</pre>
With the advent of Windows NT these ini files have been replaced by the 
registry, but the API to access them in ODBC has remained the same. Windows
has two function in odbcinst.dll that allow applications and drivers to
query and modify these files, SQLGetPrivateProfileString and 
SQLPutPrivateProfileString. 
<p>As part of unixODBC's aim of reproducing the ODBC environment on non
Windows platform's the ini files and libodbcinst provide the same format
and functionality.

<h3>System versus User</h3>
ODBC distinguishes between two types of ini files. System ini files are
designed to be accessible but not modifiable by any user, and user files 
are private to a particular user, and may be modified by that user.

<p>The system files are odbcinst.ini and odbc.ini (note no leading dot), 
and the user file is ~/.odbc.ini in each user's home directory (note 
leading dot).

<p>The system file odbcinst.ini contains information about ODBC drivers 
available to all users, and the odbc.ini file contains information about
DSN's available to all users. These &quot;System DSN's&quot; are useful
for application such as web servers that may not be running as a real user
and so will not have a home directory to contain a .odbc.ini file.

<p>A good example of this is Apache and PHP with ODBC support. When the
http server is first started it calls SQLAllocEnv as root. it then at a
later time changes to the specified user (in my case nobody) and calls
SQLConnect. If the DSN's was not a system DSN then this fails.

<h3>FILEDSN's</h3>
ODBC 3 also has a third sort of DSN, a file DSN. These store the connection
information in a file that may be accessible to anyone. unixODBC does not
at this time support FILEDSN's but it will when I get around to it. They
are useful things but of less use to UNIX's than NT. Because of the MS view
that everyone should have Windows on there desk, each workstation will have
it's own registry with it's own set of system and user DSN's that can not
be used by other workstations. File DSN's are a fix to allow the information
to be stored in a central server that is accessible to all the workstations.

<h3>Why not vi ?</h3>
All the configuration files needed by unixODBC are plain text files, so there
is no reason that you can not use your favorite text editor to setup the files.
<p>
However since beta 1.6 the location of the system files odbcinst.ini and
odbc.ini are determined by the configure script. The default location is
/usr/local/etc, and if a prefix is specified the location is {prefix}/etc. 
The location of the etc path can be broken out of the normal prefix tree
by specifying --sysconfdir=DIR, so the following will expect the system
files to be in the same location as pre 1.6 builds.
<pre>./configure --sysconfdir=/etc</pre>
The upshot of all this is that if you use odbcinst to configure the files
you can be sure that the same path to the files will be used as are used by
the driver manager, so the modifications will take effect.

Ok now we know a bit of the history of ini files and ODBC so now we need to
get to the bit that is actually of use. What you put in them.

<h4>odbcinst.ini</h4>

This contains a section heading that provides a name for the driver, so
for the example below PostgreSQL to indicate a Postgres driver. The
following lines contain a description and then the important bits. The
Driver and Setup paths point to the ODBC driver and setup libs. The
setup lib is used when you click on Add in ODBCConfig to add a new DSN, 
but as this document is about not using the GUI tools, this is not
that important for us. Far more important is the Driver entry (vital in fact)
This is the library that the driver manager will dynamically load when 
SQLConnect or SQLDriverConnect is called for that DSN. If this points
to the wrong place the DSN will not work. If the dlopen() fails the DSN will 
not work. The fileusage entry is added by the odbcinst program, so if 
you are using a text editor, you will need to add it yourself.
<pre>
[PostgreSQL]
Description     = PostgreSQL driver for Linux & Win32
Driver          = /usr/local/lib/libodbcpsql.so
Setup           = /usr/local/lib/libodbcpsqlS.so
FileUsage       = 1
</pre>

<h4>templates</h4>

odbcinst expects to be supplied with a template file. If you are adding a
driver for the above entry the template file would contain the following
<pre>
[PostgreSQL]
Description     = PostgreSQL driver for Linux & Win32
Driver          = /usr/local/lib/libodbcpsql.so
Setup           = /usr/local/lib/libodbcpsqlS.so
</pre>

and you would invoke odbcinst with the following arguments, assuming that 
you have created a file template_file with the above entries in.
<pre>
odbcinst -i -d -f template_file
</pre>
The args to odbcinst are as follows
<p>-i install 
<br>-d driver
<br>-f name of template file
<p>

<h4>Threads</h4>
Since 1.6 if the driver manager was built with thread support you may
add another entry to each driver entry. For example
<pre>
[PostgreSQL]
Description     = PostgreSQL driver for Linux & Win32
Driver          = /usr/local/lib/libodbcpsql.so
Setup           = /usr/local/lib/libodbcpsqlS.so
<b>Threading       = 2</b>
</pre>

This entry alters the default thread serialization level. More details
can be found in the file DriverManager/__handles.c in the source tree.

<h4>[.]odbc.ini</h4>
The contents of the odbc.ini files are a bit more complicated, but they follow
just the same format as the odbcinst.ini entries. These are complicated by each
driver requiring different entries. The entries for all the drivers supplied 
with the distribution are included below for reference. The entries may be
added in the same way using odbcinst, or a text editor. A sample entry
to match the above driver could be
<pre>
[PostgreSQL]
Description         = Test to Postgres
Driver              = PostgreSQL
Trace               = Yes
TraceFile           = sql.log
Database            = nick
Servername          = localhost
UserName            =
Password            =
Port                = 5432
Protocol            = 6.4
ReadOnly            = No
RowVersioning       = No
ShowSystemTables    = No
ShowOidColumn       = No
FakeOidIndex        = No
ConnSettings        =
</pre>

And this may be written to a template file, and inserted in the ini file
for the current user by
<pre>
odbcinst -i -s -f template_file
</pre>

The individual entries of course may vary.

<p>The Driver line is used to match the [section] entry in the odbcinst.ini
file and the Driver line in the odbcinst file is used to find the
path for the driver library, and this loaded and the connection is then
established. It's possible to replace the driver entry with a path to
the driver itself. This can be used, for example if the user can't get
root access to setup anything in /etc (less important now because of
the movable etc path). For example

<pre>
[PostgreSQL]
Description         = Test to Postgres
Driver              = /usr/local/lib/libodbcpsql.so
Trace               = Yes
TraceFile           = sql.log
Database            = nick
Servername          = localhost
UserName            =
Password            =
Port                = 5432
Protocol            = 6.4
ReadOnly            = No
RowVersioning       = No
ShowSystemTables    = No
ShowOidColumn       = No
FakeOidIndex        = No
ConnSettings        =
</pre>

<h3>Templates</h3>

The templates for the included drivers are...

<h4>Postgress</h4>
<pre>
[PostgreSQL]
Description         = Test to Postgres
Driver              = PostgreSQL
Trace               = Yes
TraceFile           = sql.log
Database            = nick
Servername          = localhost
UserName            =
Password            =
Port                = 5432
Protocol            = 6.4
ReadOnly            = No
RowVersioning       = No
ShowSystemTables    = No
ShowOidColumn       = No
FakeOidIndex        = No
ConnSettings        =
</pre>

<h4>Mini SQL</h4>
<pre>
[Mini SQL]
Description     = MiniSQL
Driver          = MiniSQL
Trace           = No
TraceFile       =
Host            = localhost
Database        =
ConfigFile      =
</pre>

<h4>MySQL</h4>
<pre>
[MySQL]
Description     = MySQL
Driver          = MySQL
Trace           = No
TraceFile       =
Host            = localhost
Port            =
Socket          =
Database        =
</pre>

<h4>NNTP driver</h4>
<pre>
[nntp Data Source]
Description     = nntp Driver
Driver          = nntp Driver
Trace           = No
TraceFile       =
Host            = localhost
Database        =
Port            =
</pre>

<h4>Sybase SQL Anywhere 5.0</h4> Thanks Greg.
<pre>
[Sybase SQL Anywhere 5.0]
Driver=Sybase SQL Anywhere 5.0
Description=Sybase SQL Anywhere 5.0 ODBC Driver
Userid=dba
Password=sql
DatabaseFile=sademo.db
</pre>

Hopefully this will be of some use to someone... <a href="mailto:nick@lurcher.org">Nick Gorham</a>

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