UniBasic Commands Reference - Rocket Software

Parameter Description
Examples
In the following example, the program segment reads CLIENT.NAME from the
CLIENTS file, record ID 10034, attribute 2. If the record exists, UniData appends the
attribute to string NAME.ARRAY1 using the short form of the replace command.
Otherwise, UniData executes the ELSE clause.
1-648 UniBasic Commands Reference
ON ERROR statements Specifies statements to execute if the READV statement fails
with a fatal error because the file is not open, an I/O error occurs,
or UniData cannot find the file.
If you do not specify the ON ERROR clause and a fatal error
occurs, the program terminates.
THEN statements END THEN executes if the read is successful. END is required to
terminate multiline THEN statements.
ELSE statements END ELSE executes if the read is not successful or the record does not
exist. END is required to terminate multiline ELSE statements.
READV Parameters (continued)
NAME.ARRAY1 = "Smith Jones Brown"
OPEN "CLIENTS" TO CLIENT.FILE ELSE STOP
READV CLIENT.NAME FROM CLIENT.FILE,"10034",2 THEN
NAME.ARRAY1 = CLIENT.NAME
PRINT NAME.ARRAY1
END ELSE
PRINT 'NO FILE FOR CLIENT ':CLIENT.ID
END
In the next example, you can use the READV command with an attribute.expr of 0
to verify that a record exists (for example, if you are assigning IDs sequentially in the
CLIENTS file). Each time you need to create a new ID, you need to verify that the
ID you selected is not in use. The following code accomplishes this task, incrementing
the ID until an ID is available.
LOOP
READV CHECK FROM CLIENT,NEXT.ID,0 ELSE CHECK = 0
UNTIL CHECK NE 0 DO
NEXT.ID += 1
REPEAT CLIENT.ID = NEXT.ID