basic.read Statement/BASIC Program

basic.read

Command basic.read Statement/BASIC Program
Applicable release versions: AP, R83
Category BASIC Program (486)
Description reads an item as a dynamic array and stores the item as a string. Each attribute is automatically an element of the dynamic array variable and may be referenced with the appropriate intrinsic functions.

If the file.variable parameter is not specified, the default file.variable is used.

The "else" clause is taken when the item is not on file.

The "then" clause is taken when the item is read successfully.

See the "then/else construct" for an explanation on the use of "then" and "else" clauses in statements that allow or require them.

The "readu" statement is identical to the "read" statement, except that the item is "locked", preventing access to that item by any other process. Note that in R83 implementations, the entire group in which the item was found is locked.

The "locked" statements are executed if the item exists and is already locked by another process or by the current process at a different level. "system(0)", in the "locked" clause, returns the port number which has the item locked. At the termination of the program, "readu" unlocks the item.

If a binary item is read, "system(0)" is set to 10. The variable string consists of the hex fid in attribute 1 and the hex frame in attribute 2.

In Advanced Pick (AP) implementations, this statement may optionally be written "matread" or "read". If "mat" is omitted, a matrix read can be determined by the definition of the variable, "array.variable". If no "dim" statement appears, it is automatically treated as a "dynamic" array.
Syntax read{u} dynamic.array from {file.variable,} id.expression {locked statement{s}} {then | else statement.block}
Options
Example
open 'customer' to customer.file else stop 201, 'customer'
item = ''
crt 'enter customer id ':
input item.id
read item from customer.file,item.id else stop 202,item.id
print 'the customer name is ':item<1>

This example opens the "customer" file and prompts the operator for 
the customer's item-id.  If the read is scuccessful, the customer name in 
attribute 1 is displayed.

file customer 
crt 'enter customer id ':
input item.id
read customer from item.id else stop 202,item.id
print 'the customer name is ':customer(name)

This example used the "file" statement to bind the 
"customer" file to this program. It prompts for the item-id, reads 
the item and prints the name. The "file" statement allows 
dictionary-type references to the read data item.
Purpose
Related basic.then/else.construct
basic.matread
basic.readu
basic.write
statement.block
basic.default.files
basic.statements
basic.array.references
basic.replace
array
basic.array.references
basic.<
basic.>
basic.id.expression
basic.open
basic.file.variable
basic.array.dynamic
basic.locked
basic.array.variable
basic.extract
basic.delete.function
basic.file
basic.readv
basic.begin.work