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ODBC - A Windows ODBC file server


odbc.exe [ -d ] [ -p port ] [ -u user ]


Odbc is a file server that runs under Windows and exports a 9P namespace (see intro(5)). An Inferno process that mounts the namespace can use it to manipulate Windows ODBC databases.

The -d option causes odbc to print debugging information.

The -p option gives the port number to listen on for connections. The default is 6700.

By default, the user inferno owns the files in the name space. The -u option makes user own the files instead.

Name space
Odbc presents the following name space:












The top level read-only file nclients contains the current number of active clients on the server.

The top level db directory contains a new file and subdirectories numbered n from zero to the maximum number of configured conversations.

Opening the new file reserves a conversation, represented by one of the numbered directories. The resulting file descriptor will be open on the control file, ctl, of the newly allocated conversation. Reading the ctl file returns a text string representing the number of the conversation. A conversation is used to converse with the server - in ODBC terms it is equivalent to obtaining a connection handle. This is the level at which ODBC transactions are managed.

A conversation is controlled by writing text strings to the associated ctl file. ODBC commands may be sent to the server by writing them, as text strings, to the cmd file. For commands that return a record set, the results may be read from the data file; each read returning a single record. If a command results in an error, the write to the cmd file will fail. The full ODBC error message can be obtained by reading the error file. A conversation remains open while at least one of the ctl, cmd or data files remains open.

The following commands can be written to the ctl file:

connect datasource [user!auth]
Connect to the ODBC datasource using the username and authentication, if given.
Disconnect from the datasource.
Reads from the data file will return data in a fixed format. The format can be read from the format file after writing the command to the cmd file and before reading the data from the data file.
float [fs< [rs<]]
Reads from the data file will return data using the character fs to separate fields and the character rs to separate records. The default values for fs and rs are the pipe symbol '|' and the newline character.
trans begin
Enter ODBC manual-commit mode for transactions. A transaction will not complete until one of trans commit or trans rollback is written to the ctl file.
trans auto
Enter ODBC auto-commit mode for transactions (the default). Each database statement is wrapped by a transaction that is automatically commited when the statement is executed.
trans commit
Commit a transaction when in manual-commit mode.
trans rollback
Rollback a transation when in manual-commit mode.

Once a conversation has been established and transaction mode and output formats determined the cmd file is used to send ODBC commands to the server. The following commands can be written to the cmd file:

The result of calling the ODBC API function SQLTables is returned in the data file.
columns tablename
The result of calling the ODBC API function SQLColumns with the given tablename as a parameter is returned in the data file.
any ODBC command
Any ODBC command written to the cmd file is passed to the ODBC API function SQLExecDirect. This most commonly includes select, update, insert, and delete commands.

The format file is used to determine column names and how to extract individual columns from the record read from the data file when using fixed format output. A read of it gives a single record read returning one line for each column in the result data. Each line has three components separated by a single space: a number giving the character position of the start of the field in the result data, a number giving the character position one beyond the end of the field in the result data, and the field name.

The result of database enquiries can be read from the data file. After writing a command that returns data to the cmd file, reads from the data file will return the results one record at a time. When the last record has been read the following read will return zero bytes indicating the end of the data.

The read-only file sources gives a newline separated list of sources. Each line consists of the source name and the source type separated by a colon.

The read-only file status return the status of the current conversation.


For example, the Inferno shell can be used to retrieve values from a database. The shell commands:

mount -A tcp!localhost!6700 /n/remote
	echo -n 'float' > $d/ctl
	echo -n 'connect cellar' > $d/ctl
	echo -n 'select name from wine' > $d/cmd
	cat $d/data
} < /n/remote/db/new

produces the output:

Jo. Riesling
Fume Blanc
Wh. Burgundy
Cab. Sauvignon
Pinot Noir

Here the server has been started on the local machine, listening on port 6700 for network connections. The braced block and the redirection from /n/remote/db/new reserve a conversation with the server and ensures that it remains open for the duration of the execution of the set of commands within the block. The -A option to mount is used because this server can not authenticate a connection.




bind(1), sys-bind(2), intro(5), db(7), dbsrv(7), svc(8)

ODBC(10.4 ) Rev:  Tue Mar 31 02:42:39 GMT 2015