= halstreamer(1)


== NAME

halstreamer - stream file data into HAL in real time


== SYNOPSIS

*halstreamer* [_options_]


== DESCRIPTION

*streamer*(9) and *halstreamer* are used together to stream data
from a file into the HAL in real time.  *streamer* is a realtime HAL
component that exports HAL pins and creates a FIFO in shared memory.
*hal_streamer* is a user space program that copies data from stdin into
the FIFO, so that *streamer* can write it to the HAL pins.


== OPTIONS

*-c* _CHAN_::

    Instructs *halstreamer* to write to FIFO _CHAN_.  FIFOs are numbered
    from zero, and the default value is zero, so this option is not
    needed unless multiple FIFOs have been created.

_FILENAME_::

    Instructs *halsampler* to read from _FILENAME_ instead of from stdin.


== USAGE

A FIFO must first be created by loading *streamer*(9) with *halcmd loadrt*
or a *loadrt* command in a .hal file.  Then *halstreamer* can be invoked
to begin writing data into the FIFO.

Data is read from stdin, and is almost always either redirected from
a file or piped from some other program, since keyboard input would be
unable to keep up with even slow streaming rates.

Each line of input must match the pins that are attached to the FIFO,
for example, if the *streamer* config string was "ffbs" then each line
of input must consist of two floats, a bit, and a signed integer, in that
order and separated by whitespace.  Floats must be formatted as required
by *strtod*(3), signed and unsigned integers must be formatted as required
by *strtol*(3) and *strtoul*(3), and bits must be either '0' or '1'.

Input lines that begin with '#' will be treated as comments and silently
skipped.

*halstreamer* transfers data to the FIFO as fast as possible until the
FIFO is full, then it retries at regular intervals, until it is either
killed or reads EOF from stdin.  Data can be redirected from a file or
piped from some other program.

The FIFO size should be chosen to ride through any momentary disruptions
in the flow of data, such as disk seeks.  If the FIFO is big enough,
*halstreamer* can be restarted with the same or a new file before the
FIFO empties, resulting in a continuous stream of data.

The data format for *halstreamer* input is the same as for *halsampler*(1)
output, so 'waveforms' captured with *halsampler* can be replayed using
*halstreamer*.


== EXIT STATUS

If a problem is encountered during initialization, *halstreamer* prints
a message to stderr and returns failure.

If a badly formatted line is encountered while writing to the FIFO, it
prints a message to stderr, skips the line, and continues (this behavior
may be revised in the future).

Upon reading EOF from the input, it returns success.  If it is terminated
before the input ends, it returns failure.


== SEE ALSO

*streamer*(9) *sampler*(9) *halsampler*(1)


== AUTHOR

Original version by John Kasunich, as part of the LinuxCNC project.
Improvements by several other members of the LinuxCNC development team.


== REPORTING BUGS

Report bugs to jmkasunich AT users DOT sourceforge DOT net


== COPYRIGHT
Copyright © 2006 John Kasunich.  This is free software; see the
source for copying conditions.  There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

