filel - printer utilities
Filel sets the current file to the line printer for subsequent I/O (see
initio(io)). If the line printer is not yet open, this function opens it.
Under UNIX, a variety of spoolers and drivers are used to interface printers,
so a flexible system is needed to open the printer. The value of the
environment variable LPR is taken as a command to the UNIX shell (see
sh(1)). This command must read data from its standard input and see
that it arrives at the printer. This function locates and reads the environment
variable, creates a pipe and a process and invokes the shell. This function
also creates a buffer for the pipe. Because some applications can not tolerate
delay in receiving characters at the printer, the buffer used is of trivial
length and never holds characters between I/O functions. To be effective, such
an application must assign to LPR a command which itself does not buffer data.
This function supports output to the line printer.
Lpos returns the current column number of the line printer. At the level
of the userís code, columns are numbered starting with one. If the line
printer is not yet open, this function returns one. This function implements
the BASIC LPOS function.
sh(1) in the UNIX Programmerís Manual
Filel generates error 5 (Illegal function call) if the environment
variable LPR does not exist or is empty. If the command is wrong, a subsequent
write attempt will generate an error.
The Basmark QuickBASIC Programmerís Manual