.H 1 3d .B 3d is the historical name for .IB n DFS , the multiple dimension file system. It is implemented as a shared library that is preloaded before any other shared library using the recently documented .RI ( ahem ) .B LD_PRELOAD or .B _RLD_LIST feature of the runtime linker. .B 3d intercepts pathname system calls (and other calls if tracing is turned on) and provides a logical namespace on top of the underlying physical file system. The shared library implementation currently works only on .IR bsd.i386 , .IR linux.i386 , .IR osf.alpha , .IR sun4 , .IR sol.* , and .IR sgi.* . .P .B 3d works in conjunction with .B ksh88 or .BR ksh93 . The .B 3d command with no arguments enters a .B 3d shell. The .B vpath builtin controls the logical filesystem view: .EX vpath dir_1 dir_2 .EE mounts the directory hierarchy .I dir_1 on top of .IR dir_2 . Files under .I dir_1 overlay files under .IR dir_2 . Files under .I dir_2 are readonly; any files under .I dir_2 that are modified are first copied to the corresponding place in .IR dir_1 . .I vpaths may be chained: .EX vpath dir_2 dir_3 .EE .I vpaths are per-process; every process may have a different view. .I vpaths are a handy way to separate source and generated files. Typical .B advsoft users set up .B 3d at login or .B xterm time: .EX export HOSTTYPE=$(package) vpath $HOME/arch/$HOSTTYPE $HOME .EE with source files in .LR $HOME/src/(cmd|lib)/* . .B nmake is run in .L $HOME/arch/$HOSTTYPE/src/(cmd|lib)/* and generated files (objects and executables) are dropped in the top hierarchy. .P .B 2d can prefix any command to disable .B 3d for that command: .EX 2d ls *.c .EE .P .B 3d also provides tracing, monitoring and call intercept services. .B vpm uses monitoring to graph the process and io hierarchy. The .I cs name server uses pathname call intercepts to translate network pathnames. Try this for any host: .EX cat /dev/tcp/hostname/inet.daytime .EE
