Development System - Applications
Applications are usually kept in directories reserved for them. Applications supplied by the system for general use, including program development, are found in /usr/bin. Applications added by system administrators for a specific host computer or local network are often found in /usr/local/bin or /opt.
Administrators favor /usr/local, as it keeps vendor-supplied files and later additions separate from the applications supplied by the system. Keeping /usr organized in this way may help when the time comes to upgrade the operating system, since only /usr/local need be preserved. We recommend that you compile your applications to run and access required files from the /usr/local hierarchy.
Additional features and programming systems may have their own directory structures and program directories. Chief among these is the X Window System, which is commonly installed in the /usr/X11 directory. Alternative locations include /usr/X11R6 for Revision 6, also used by the XFree86 variant for Intel processors distributed by the XFree consortium as well as many Linux distributions. Other UNIXlike systems may choose different locations, such as /usr/openwin for Sun’s Open Windows provided with Solaris.
The GNU compiler system’s driver program, gcc (which we used in our programming example earlier in the chapter), is typically located in /usr/bin or /usr/local/bin, but it will run various compilersupport applications from another location. This location is specified when you compile the compiler itself and varies with the host computer type. For Linux systems, this location might be a version-specific subdirectory of /usr/lib/gcc-lib/. On one of the author’s machines at the time of writing it is /usr/lib/gcc-lib/i486-suse-linux/3.3/. The separate passes of the GNU C/C++ compiler, and GNU-specific header files, are stored here.