There are two problems in resolving path names. First, an object may reside in a different place in this release than it did in the SunOS 4.x release. For example, a command found in /usr/bin in the SunOS 4.x release may be in /usr/ucb in the Solaris 2.x release. The Source Compatibility Package resolves this difference by setting up symbolic links whenever possible so that the applications, using the old path names, can access the files.
Second, many commands in this release are not compatible with their SunOS 4.x counterparts. As part of the Source Compatibility Package, a set of SunOS 4.x-compatible command binaries is also installed. If applications specify only the command name to be executed (and not a path name), the Binary Compatibility Package reads the PATH environment variable to find the correct command. For this reason the PATH variable should be set correctly before running the application.
For example, to get the default SunOS 4.x behavior, specify /usr/ucb before /usr/bin in PATH; otherwise, the default Solaris 2.x behavior is provided.
When a full path name is given, the Binary Compatibility Package interprets the path name as given. When the path begins with /usr/5bin, the default Solaris 2.x version of the command is executed; otherwise, the Source Compatibility Package version is executed. A relative path name is interpreted as given.
Starting in Solaris 2.5, five commands are relocated from /usr/ucb to /usr/bin to accommodate shell scripts written with absolute paths. These commands are arch(1), hostid(1)), hostname(1), mach(1), and pagesize(1)).