postio(1)

postio -- serial interface for PostScript printers

Synopsis

postio -l line [options] [files]

Description

postio sends files to the PostScript printer attached to line. If no files are specified the standard input is sent. The first group of options should be sufficient for most applications:

-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.
-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 doesn't begin with a / it may be treated as a Datakit destination.
-q: 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 num: Set the internal buffer size for reading and writing files to num bytes. By default num is 2048 bytes.
-D: Enable debug mode. Guarantees that everything read on line will be added to the log file (standard error by default).
-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:

-i: 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.
-t: 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:

-S: 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.

Diagnostics

An exit status of 0 is returned if the files ran successfully. System errors (such as an inability to open the line) set the low order bit in the exit status, while PostScript errors set bit 1. An exit status of 2 usually means the printer detected a PostScript error in the input files.

References

download(1), dpost(1), postdaisy(1), postdmd(1), postmd(1), postprint(1), postreverse(1), posttek(1)

Notices

The input files are handled as a single PostScript job. Sending several different jobs, each with their own internal end of job mark (^D) is not guaranteed to work properly. postio may quit before all the jobs have completed and could be restarted before the last one finishes.

All the capabilities described above may not be available on every machine or even across the different versions of the UNIX system that are currently supported by the program. For example, the code needed to connect to a Datakit destination may work only on System V and may require that the DKHOST software package be available at compile time.

There may be no default line, so using the -l option is strongly recommended. If omitted, postio may attempt to connect to the printer using the standard output. If Datakit is involved, the -b option may be ineffective and attempts by postio to impose flow control over data in both directions may not work. The -q option can help if the printer is connected to RADIAN. The -S option is not generally recommended and should be used only if all other attempts to establish a reliable connection fail.

Examples

Run as a single process at 9600 baud and send file1 and file2 to the printer attached to /dev/tty01:

postio -l /dev/tty01 file1 file2

Same as above except two processes are used, the internal buffer is set to 4096 bytes, and data returned by the printer gets put in file log:

postio -R2 -B4096 -l/dev/tty01 -Llog file1 file2

Establish an interactive connection with the printer at Datakit destination my/printer:

postio -i -l my/printer

Send file program to the printer connected to /dev/tty22, recover any data in file results, and put log messages in file log:

postio -t -l /dev/tty22 -L log program > results