CSC Advanced Unix Programming, Fall, 2008 Welcome back to UNIX System Programming! Monday, September 15, class 4

UNIX random access files lseek(int fd, int offset, int whence) seeks within a file, offset is location to which to go whence is one of SEEK_SET (from start), SEEK_CUR (from current), SEEK_END (from end). Do not use O_APPEND! It seeks to the end of file on appends. See ~parson/UnixSysProg/lecture4/seeklock/.

fcntl() (file control) is a catch all, like ioctl() (I/O control) int fcntl(int fildes, int cmd, /* arg */...); F_GETLK, F_SETLK, F_SETLKW manipulate file locks. Third argument to F_SETLK[W] must be a * struct flock. short l_type; /* lock operation type */ short l_whence; /* SEEK_SET, SEEK_CUR, or SEEK_END */ off_t l_start; /* starting offset from base */ off_t l_len; /* lock length; l_len == 0 means until end of file */ int l_sysid; /* system ID running process holding lock */ pid_t l_pid; /* process ID of process holding lock*/ Struct l_type field gets F_RDLCK (shared), F_WRLCK (exclusive), or F_UNLCK (unlock).

A multi-process (and eventually networked) game framework /export/home/faculty/parson/gchess GNU chess is a terminal I/O chess game gzcat gnuchess-5.07.tar.gz | tar xvf – cd gnuchess-5.07 ;./configure ; gmake cd src ; export PATH=“`pwd`:${PATH}” OR cd src ; setenv PATH =“`pwd`:${PATH}” gnuchess builds in the src/ directory.

Play terminal I/O chess and examine its process gnuchess show board, e2 e4, etc. ps -flu parson – inspect PID and PPID 0 O parson gnuchess pfiles It is using only stdin, stdout and stderr! They are all type S_IFCHR. “quit” or “exit” to get out

xboard is a GUI that runs and displays gnuchess cd /export/home/faculty/parson/gchess gzcat xboard tar.gz | tar xvf – cd xboard ;./configure ; gmake export PATH=“`pwd`:${PATH}” OR setenv PATH =“`pwd`:${PATH}” xboard builds in the xboard / directory. Invoking “xboard” requires having Hummingbird -> Exceed or another X11 display server running on your terminal.

xboard under X11 on Sun

Processes under xboard ps –flu shows three processes 0 S parson /xboard 0 S parson /bin/sh /export/home/faculty/parson 0 O parson gnuchess xboard shows stdin, stdout and stderr open All 3 are type S_IFIFO

Processes under xboard continued shows four open file descriptors fd 0, 1 and 2 are S_IFIFO fd 19: S_IFREG, O_RDONLY|O_LARGEFILE FD_CLOEXEC shows 8 open file descriptors It is good that we don’t have to analyze X11 communication protocols in order to get started! S_IFCHR, S_IFSOCK, S_IFDOOR, S_IFIFO

Assignment: Spy on GNU chess! Your initial assignment is to write an interceptor that sits between xboard and gnuchess and logs interactions while you play chess. Use your trace log plus source code and docs to understand the xboard gnuchess command and results protocol. xboard interceptor gnuchess xboard » stdin log, stdout log, stderr log for gnuchess

The bigger assignment: Sound Install ChucK on a machine with some speakers. My chess program, linked to my web page, as a ChucK directory, with a README. Open Sound Control (OSC) over UDP datagrams  a ChucK process running my sound generator  speakers But, Professor Parson, where do the OSC/UDP datagrams comes from?

A Python chess-to-music game One or more Python game GUIs  Python game server that takes commands from command line (stdin / stdout), and also accepts GUI commands from UDP datagrams. This Python program generates OSC/UDP  ChucK. The command line server, like gnuchess, is a stdin / stdout / stderr process.

Project goals Allow Python chess-to-music program to play a human against the machine (gnuchess). Support alternative, networked GUI (in Python) for gnuchess. Have some fun while learning fork, exec, file IO, sockets, networking and multithreading. Live long and prosper.

Summary Ultimately you are creating a game framework to integrate two or more running games. An ideal goal would be to allow support for different protocols using a plugin parser. The immediate goal is to intercept, redirect, etc. commands passing between xboard gnuchess, and also my Python game server Python GUI, and to translate between them.