ref: babf901b4a508c3ec5d1f89655f10377bbdf9637
dir: /man/10/odbc/
.TH ODBC 10.4
.SH NAME
ODBC \- A Windows ODBC file server
.SH SYNOPSIS
.B odbc.exe
[
.B -d
] [
.BI -p " port"
] [
.BI -u " user"
]
.SH DESCRIPTION
.I Odbc
is a file server that runs under Windows and
exports a 9P namespace
(see
.IR intro (5)).
An Inferno process that mounts the namespace
can use it to manipulate Windows ODBC databases.
.PP
The
.B -d
option causes
.I odbc
to print debugging information.
.PP
The
.B -p
option gives the port number to listen on for connections. The default is 6700.
.PP
By default, the user
.B inferno
owns the files in the name space.
The
.B -u
option makes
.I user
own the files instead.
.SS Name space
.I Odbc
presents the following name space:
.PP
.nf
.BI /nclients
.BI /db
.BI /db/new
.BI /db/ n
.BI /db/ n /cmd
.BI /db/ n /ctl
.BI /db/ n /data
.BI /db/ n /error
.BI /db/ n /format
.BI /db/ n /sources
.BI /db/ n /status
.fi
.PP
The top level read-only file
.B nclients
contains the current number of active clients on the server.
.PP
The top level
.B db
directory contains a
.B new
file and subdirectories numbered
.B n
from zero to the maximum number of
configured conversations.
.PP
Opening the
.B new
file reserves a conversation, represented
by one of the numbered directories. The resulting file descriptor will be open
on the control file,
.BR ctl ,
of the newly allocated conversation.
Reading the
.B 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.
.PP
A conversation is controlled by writing text strings to the
associated
.B ctl
file. ODBC commands may be sent to the
server by writing them, as text strings, to the
.B cmd
file.
For commands that return a record set, the results may be read
from the
.B data
file; each read returning a single record.
If a command results in an error, the write to the
.B cmd
file
will fail. The full ODBC error message can be obtained by reading
the
.B error
file.
A conversation remains open while at least one of the
.BR ctl ,
.B cmd
or
.B data
files remains open.
.PP
The following commands can be written to the
.B ctl
file:
.TP
.B connect " datasource" " [user!auth]"
Connect to the ODBC datasource using the username and authentication, if given.
.TP
.B disconnect
Disconnect from the datasource.
.TP
.B fixed
Reads from the
.B data
file will return data in a fixed format. The format can
be read from the
.B format
file after writing the command to the
.B cmd
file and before reading the data from the
.B data
file.
.TP
.B float " [fs< [rs<]]"
Reads from the data file will return data using the character
.B fs
to separate fields and the character
.B rs
to separate records.
The default values for
.B fs and
.B rs
are the pipe symbol '|'
and the newline character.
.TP
.B trans " begin"
Enter ODBC manual-commit mode for transactions. A transaction will
not complete until one of
.B trans commit
or
.B trans rollback
is written to the
.B ctl
file.
.TP
.B 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.
.TP
.B trans " commit"
Commit a transaction when in manual-commit mode.
.TP
.B trans " rollback"
Rollback a transation when in manual-commit mode.
.PP
Once a conversation has been established and transaction mode and
output formats determined the
.B cmd
file is
used to send ODBC commands to the server.
The following commands can be written to the
.B cmd
file:
.TP
.B tables
The result of calling the ODBC API function SQLTables is returned
in the
.B data
file.
.TP
.B columns " tablename"
The result of calling the ODBC API function SQLColumns with the
given
.B tablename
as a parameter is returned in the
.B data
file.
.TP
.B any " ODBC" " command"
Any ODBC command written to the
.B cmd
file is passed
to the ODBC API function SQLExecDirect. This most commonly includes
select, update, insert, and delete
commands.
.PP
The
.B format
file is used to determine column names and how to extract
individual columns from the record read from the
.B 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.
.PP
The result of database enquiries can be read from the
.B data
file.
After writing a command that returns data to the
.B cmd
file,
reads from the
.B 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.
.PP
The read-only file
.B sources
gives a newline separated list of sources. Each line consists
of the source name and the source type separated by a colon.
.PP
The read-only file
.B status
return the status of the current conversation.
.SH EXAMPLE
For example, the Inferno shell can be used to retrieve
values from a database. The shell commands:
.PP
.EX
mount -A tcp!localhost!6700 /n/remote
{
d=/n/remote/db/`{cat}
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
.EE
.PP
produces the output:
.PP
.EX
Chardonnay
Jo. Riesling
Fume Blanc
Wh. Burgundy
Gewurztraminer
Cab. Sauvignon
Pinot Noir
Zinfandel
Gamay
.EE
.PP
Here the server has been started on the local machine, listening on port
6700 for network connections.
The braced block and the redirection from
.B /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
.B -A
option to mount is used because this server can not
authenticate a connection.
.SH SOURCE
.B /tools/odbc/odbc.c
.SH SEE ALSO
.IR bind (1),
.IR sys-bind (2),
.IR intro (5),
.IR db (7),
.IR dbsrv (7),
.IR svc (8)