basic.readt Statement/BASIC Program

basic.readt

Command basic.readt Statement/BASIC Program
Applicable release versions: AP, R83
Category BASIC Program (486)
Description reads a tape record and assigns the value returned to a specified variable.

The length of the tape record is specified by the most recently executed "t-att" command.

The "then" clause is taken if the operation is successful.

Either "else" or "onerr" can be specified, but not both. If the tape unit has not been attached or if an end-of-file (EOF) mark is read, the "else" or "onerr" clause, if present, is executed. In addition, the "onerr" statement can be used to check for end-of-tape (EOT), tape unit not ready, parity error, or block transfer error. See the system(0) function.

See the "then/else construct" for an explanation on the use of "then" and "else" clauses in statements that allow or require them.
Syntax readt variable [then | else | onerr statement.block]
Options
Example
execute 't-att'
rewind else stop
eot=0
loop
  readt rec else eot=1
until eot do
  print trim(rec[1,25])
repeat
Reads a series of tape records and displays the first 25 bytes of each record.  
The "readt" else clause is usually taken when an end-of-tape or 
end-of-data condition is reached.  The "system(0)" function indicates 
whether there are any other unexpected problems.
Purpose
Related basic.rewind
basic.then/else.construct
basic.then
statement.block
tcl.t-att
basic.weof
basic.writet
basic.onerr
basic.statements
basic.readtl
basic.readtx
tcl.t-select
tcl.t-stat
basic.system
tcl.set-sct