F-OPEN

Clears the file buffer and opens a file to allow reads and writes.

Syntax

F-OPEN file-buffer-number file-specifier
alt-cmd

F-O file-buffer-number file-specifier
alt-cmd

Syntax Elements

file-buffer-number
The number of the file buffer to which the file is assigned. Valid numbers are 1 to 47, but note that 19 and 20 are reserved for system Procs.

file-specifier The name of the file to be opened, as defined in Conventions.

file-specifier can be a literal (not enclosed in quotes) or can be a direct or indirect reference to a buffer or select register that contains it.

alt-cmd The command(s) to be executed if the named file cannot be opened. Must be on the line immediately after the command itself.

Operation

The F-OPEN command must always followed by a command to be executed if the OPEN fails.

After a file has been opened, it remains open for the rest of the execution of the Proc, including Proc to Proc transfers.

File buffers can be reused by issuing another F-OPEN statement.

If you try to open a nonexistent file, the command(s) on the line immediately following the F-OPEN command is executed.

If the file is opened successfully, the command(s) on the line immediately following the F-OPEN is skipped, and execution begins with the next line.

Comments

If you are only processing one item from a file, the FB command is preferable to an F-OPEN, F-READ command sequence.

Examples

001 PQN

002 F-OPEN 1 %1

003 XCannot open file

004 OFile opened successfully!

.

If the file represented by %1 cannot be opened, the message, "Cannot open file" is displayed and the Proc is exited. Otherwise, execution continues with the message "File opened successfully!"

001 PQN
002 F-OPEN 2 CARS
003 G 30
004 T C,(10,10),"Enter item-id of car you want",S5,+
.

If the CARS file cannot be opened, then control is transferred to label 30. Otherwise, execution continues with the display on line 004.