strange behavior on port send

Garry Hodgson <>
Fri May 18 19:58:28 CEST 2001


i'm trying to interface to an external application, and having
some problems.  i'm using code derived from the "Section 4. Ports"
example in the interoperability tutorial.  the external application
is a colleague's, and i wanted to use the port mechanism to make
it easy for her to interface.

if i build the external program in python, and have it read
its input using the standard python readlines() call, the programs
work just fine.  to make this work, i use the (default) stream and 
use_stdio options in the open_port() call.

so now, i'm trying instead to connect it to another
program, written in c.  if i run the program by
hand, and type commands at it, it works just fine.
if i have the erlang open_port() spawn it, when i 
send a message i get:

=ERROR REPORT==== 19-May-2001::01:38:50 ===
Bad value on output port '/usr/local/wnet/srv/bravosrv -e
/usr/local/wnet/srv/sample.wnet'

i've tried all variations i can think of to fix this.
i use an explicit read() call, rather than stdin, though
i get the same behavior if i use gets().  i've change it
to use the {packet, 2} option on the erlang side instead,
with the read_cmd() call from the tutorial's sample code.
same thing.

when i first started this stuff, i compiled and ran the 
tutorial's example code, and it worked fine.  so i know
there's nothing inherent in talking to c that is a problem.
the program i'm trying to talk to does nothing nasty that i
can see, but it calls some functions to initialize a large
backend set of libraries, written in a mix of c and tcl,
and i'm wondering if maybe there's some ugliness being done
to the file descriptors behind our backs.

does anyone have any ideas?

thanks

-- 
Garry Hodgson                   sometimes we ride on your horses
Senior Hacker                   sometimes we walk alone
Software Innovation Services    sometimes the songs that we hear
AT&T Labs                       are just songs of our own




More information about the erlang-questions mailing list