OPEN_IN #channel, device_filename or
OPEN_IN #channel, [device_]filename (Toolkit II only) or
OPEN_IN #channel, device_filename, type (Minerva v1.80+ only)
QL ROM, Toolkit II
This command is a specialised version of OPEN which is aimed at allowing you to read data from files. This opens the specified channel (#channel must be an integer in the range 0…32767) for input only to the specified filename on the given device.
Any number of channels may be linked to a file using OPEN_IN, although if you try to use any other type of OPEN call to that filename, the error ‘in use’ will be reported.
The Toolkit II variant of this command supports the default data device if necessary (see DATAD$), but in any case, if the file does not exist (either on the specified device or on the default data device), the error ‘Not Found’ (-7) will be reported.
OPEN_IN will close a channel which is already open with the same channel number prior to opening the new channel - do not try to OPEN_IN #0 unless you have read the notes to OPEN!
On AH ROMs, if two tasks tried to read the same file at the same time, the second task was likely to miss the start of the file and read the directory header instead.
On QL ROMs (pre MG) there is a maximum of 32767 OPENs in a session.
If instead of device_filename, another type of device is used, such as scr_, OPEN_IN has the same effect as OPEN.
On v1.80 and later, a third parameter is supported by OPEN_IN as with OPEN. This means that this command (if the third parameter is used) has exactly the same effect as OPEN.
FOP_IN is an error trapped equivalent to this command. OPEN_DIR allows you to access directories on drives. OPEN contains a general description of all the open types. OPEN_NEW and OPEN_OVER are also linked with this.