UniBasic Commands Reference - Rocket Software

If the AT clause is not included, UniBasic begins reading from the current
location of the file pointer.
Because named pipes must be read from the beginning, the AT clause is not
appropriate for accessing them. If the AT clause is specified, the ON
ERROR executes, and the UniBasic STATUS function is set to 2. If the ON
ERROR clause is not included, the program aborts.
After successful execution of OSBREAD against a file that is not a named
pipe, the file pointer remains at the next byte after the data read.
Parameters
The following table describes each parameter of the syntax.
Parameter Description
var Specifies a variable to which to assign the data read.
FROM file.var Specifies a file from which to read the data.
AT byte.expr Specifies a location in the file from which to begin reading data.
If byte.expr is 0, the read begins at the beginning of the file.
When reading a named pipe, do not specify an AT clause. Pipes
are always read with no offset.
LENGTH length.expr Specifies a length of data to read from the file, starting at
byte.expr.
length.expr cannot be longer than the maximum string length
determined by your system configuration.
NODELAY Forces an immediate read of a named pipe regardless of whether
the pipe contains data. If you do not specify NODELAY, the
process attempting to read waits until the pipe is opened for
writing and data is written to it.
If filename is not a named pipe, NODELAY has no effect.
ON ERROR statements Specifies statements to execute if a fatal error occurs (if the file
is not open, or if the file is a read-only file). If you do not specify
the ON ERROR clause, the program terminates under such fatal
error conditions.
OSBREAD Parameters
OSBREAD 1-548