POSTIO(1) User Commands POSTIO(1)


postio - serial interface for PostScript printers


postio -l line [-D] [-i] [-q] [-t] [-S] [-b speed] [-B num]
[-L file] [-P string] [-R num] [file]...



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:

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

-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

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


Example 1: Examples of the postio command.

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

example% 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:

example% postio -R 2 -B 4096 -l/dev/tty01 -L log file1 file2

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

example% 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:

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


The following exit values are returned:

Successful completion.

An error occurred.


download(1), dpost(1), postprint(1), postreverse(1), attributes(7)


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.

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.

May 13, 2017 POSTIO(1)