The first group of options should be sufficient for most applications:
- Enable debug mode. Guarantees that everything read on line will be added to the
log file (standard error by default).
- Prevents status queries while files are being sent to the printer. When status queries are disabled a dummy message
is appended to the log file before each block is transmitted.
- -b speed
- Transmit data over line at baud rate speed. Recognized baud rates
are 1200, 2400, 4800, 9600, and 19200. The default speed is 9600 baud.
- -B num
- Set the internal buffer size for reading and writing files to num
bytes. By default num is 2048 bytes.
- -l line
- Connect to the printer attached to line. In most cases there is no default and postio must be able to read and write line. If the line does not begin with a / it may be treated as a Datakit destination.
- -L file
- Data received on line gets put in file. The default log file
is standard error. Printer or status messages that don't show a change in state are not normally written to file but can be forced out using the -D option.
- -P string
- Send string to the printer before any of the input files. The default string is simple PostScript code that disables timeouts.
- -R num
- Run postio as a single process if num is 1 or as separate read and
write processes if num is 2. By default postio runs as a single process.
The next two options are provided for users who expect to run postio on their own. Neither is suitable for use in spooler interface programs:
- Run the program in interactive mode. Any files are sent first and
followed by the standard input. Forces separate read and write processes and overrides many other options. To exit interactive mode use your interrupt or quit character. To get a friendly interactive connection
with the printer type executive on a line by itself.
- Data received on line and not recognized as printer or status information is written to the standard output. Forces separate
read and write processes. Convenient if you have a PostScript program that will be returning useful data to the host.
The last option is not generally recommended and should only be used if all else fails to provide a reliable connection:
- Slow the transmission of data to the printer. Severely limits throughput, runs as a single process,
disables the -q option, limits the internal buffer size to 1024 bytes, can use an excessive amount of CPU time, and does nothing in interactive mode.
The best performance will usually be obtained by using a large internal buffer (the -B option) and by running the program as separate read and write processes (the -R 2 option). Inability to fork the additional process causes postio to continue as a single read/write process. When one process is used, only data sent to the printer
is flow controlled.
The options are not all mutually exclusive. The -i option always wins, selecting its own settings for whatever is needed to run interactive mode, independent
of anything else found on the command line. Interactive mode runs as separate read and write processes and few of the other options accomplish anything in the presence of the -i option. The -t option needs a reliable two way connection to the printer and therefore tries to force separate read and write processes. The -S option relies
on the status query mechanism, so -q is disabled and the program runs as a single process.
In most cases postio starts by making a connection to line and then attempts to force the printer into the IDLE state by sending an appropriate sequence of ^T (status query), ^C (interrupt), and ^D (end of job) characters. When the printer goes IDLE, files are transmitted
along with an occasional ^T (unless the -q option was used). After all the files are sent the program waits until it's reasonably sure
the job is complete. Printer generated error messages received at any time except while establishing the initial connection (or when running interactive mode) cause postio to exit with
a non-zero status. In addition to being added to the log file, printer error messages are also echoed to standard error.