FTEST

Syntax	FTEST (name)
Location	Toolkit II

The function FTEST is designed to allow you to test for the status of a file with the specified name. It will return a value of 0 if the given name can be opened for input only. It may however return a negative number representing an error code which would result if you tried to OPEN or OPEN_IN that file.

NOTE 1

The return of -6 (channel not open) has a special meaning in relation to this function, it means that the function could not find any room in the channel table to try and access the file.

NOTE 2

Due to the nature of the command, name can be used to represent any valid device, and could therefore, for example, be used to check if a resolution of 768x280 pixels is supported:

100 a$='scr_768x280a0x0'
110 IF FTEST(a$)<0
120   a$='scr_512x256a0x0'
130 END IF
140 OPEN #3,a$

NOTE 3

On Level-2 and Level-3 devices, there is always a file with the same name as the actual name of the device (eg. ‘flp1_’). This therefore allows you to check if a medium is present in a Level-2 device:

IF FTEST(flp1\_)<0 THEN PRINT 'Please insert disk'

You must however be aware that on Level-1 devices, it is unlikely that such a file will be present and that FTEST will return -7 even if there is a disk present.

NOTE 4

FTEST will not warn you if a disk is read only, which can create problems.

CROSS-REFERENCE

FOPEN and FOP_IN allow you to open files safely. DMEDIUM_RDONLY can be used to find out if a disk is write protected.