During zxid project development phase (ongoing as of Jan 2007), most configuration related documentation will be kept as comments in zxidconf.h, which you should see.
Configuration file is line oriented. Comments can be introduced with cardinal (#) and empty lines are ignored. End of line comments are NOT supported at this time.
Each configuration option is a name=value pair. The name is the same as in zxidconf.h except that ZXID_ prefix does not appear. Only single line values are supported, but you can embed characters using URI encoding, e.g. %0a for newline. In fact, the configuration lines are treated as CGI variables, thus & can also be used as separator instead of newline (and needs to be encoded if not intended as separator).
When option is not specified, the default from zxidconf.h prevails. Thus in the following the PATH specification is redundant.
To give some idea consider following /var/zxid/zxid.conf example:
# Demo /var/zxid/zxid.conf file PATH=/var/zxid URL=https://sp.mydomain.com:8443/zxid NICE_NAME=My SP's human%0areadable name. #EOF