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The Resolver

In addition to the standard communication and network database routines in the UNIX environment, the SAS/C Library contains a complete implementation of the BSD resolver and provides the standard UNIX interface for resolver programming. This facilitates the writing of applications that communicate with Internet name servers. The resolver is compatible with the UNIX operating system because the routines are derived from the BSD network source. There are, however, three compatibility issues that should be considered:

• ASCII-to-EBCDIC translation is performed automatically by the dn_expand function, and EBCDIC-to-ASCII translation is performed by the dn_comp function. These translations should resolve any ASCII-to-EBCDIC translation problems for domain names without requiring special code in the application. The SAS/C Library can translate automatically in this instance because it recognizes that the data are intended to be ASCII text.

• Routines that are declared to be external in the BSD name server but that are not documented in the UNIX man pages (for example, the routines that print resolver debugging information) cannot be called directly in the SAS/C implementation.

• The _res variable cannot be declared directly in a program because it is implemented as a macro in SAS/C software. Include the <resolv.h> header file for a definition for the _res variable.

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