curs_print.3x man page
mcprint — ship binary data to printer
int mcprint(char *data, int len);
This function uses the mc5p or mc4 and mc5 capabilities, if they are present, to ship given data to a printer attached to the terminal.
Note that the mcprint code has no way to do flow control with the printer or to know how much buffering it has. Your application is responsible for keeping the rate of writes to the printer below its continuous throughput rate (typically about half of its nominal cps rating). Dot-matrix printers and 6-page-per-minute lasers can typically handle 80cps, so a good conservative rule of thumb is to sleep for a second after shipping each 80-character line.
The mcprint function returns ERR if the write operation aborted for some reason. In this case, errno will contain either an error associated with write(2) or one of the following:
Capabilities for printer redirection do not exist.
Couldn't allocate sufficient memory to buffer the printer write.
When mcprint succeeds, it returns the number of characters actually sent to the printer.
The mcprint call was designed for ncurses(3X), and is not found in SVr4 curses, 4.4BSD curses, or any other previous version of curses.
Padding in the mc5p, mc4 and mc5 capabilities will not be interpreted.