NAME
krb5_principal_intro – The principal handing functions. A Kerberos principal is a email address looking string that contains two parts separated by The second part is the kerberos realm the principal belongs to and the first is a list of 0 or more components. For example
lha[at] SU.SE
host /
hummel.it.su.se[at] SU.SE
host /
admin[at] H5L.ORG
See the library functions here: Heimdal Kerberos 5 principal functions