GETHOSTBYNAME(3) BSD Library Functions Manual GETHOSTBYNAME(3)

NAME
     ggeetthhoossttbbyynnaammee, ggeetthhoossttbbyynnaammee22, ggeetthhoossttbbyyaaddddrr, ggeetthhoosstteenntt, sseetthhoosstteenntt,
     eennddhhoosstteenntt, hheerrrroorr, hhssttrreerrrroorr - get network host entry

LLIIBBRRAARRYY
     Standard C Library (libc, -lc)

SYNOPSIS
     ##iinncclluuddee <>

     extern int herrno;

     struct hostent *
     ggeetthhoossttbbyynnaammee(const char *name);

     struct hostent *
     ggeetthhoossttbbyynnaammee22(const char *name, int af);

     struct hostent *
     ggeetthhoossttbbyyaaddddrr(const char *addr, socklent len, int type);

     struct hostent *
     ggeetthhoosstteenntt(void);

     void
     sseetthhoosstteenntt(int stayopen);

     void
     eennddhhoosstteenntt(void);

     void
     hheerrrroorr(const char *string);

     const char *
     hhssttrreerrrroorr(int err);

DESCRIPTION
     The ggeetthhoossttbbyynnaammee(), ggeetthhoossttbbyynnaammee22() and ggeetthhoossttbbyyaaddddrr() functions each
     return a pointer to an object with the following structure describing an
     internet host referenced by name or by address, respectively.  This
     structure contains either the information obtained from the name server,
     named(8), or broken-out fields from a line in /etc/hosts.  If the local
     name server is not running these routines do a lookup in /etc/hosts.

     struct  hostent {
             char    *hname;        /* official name of host */
             char    **haliases;    /* alias list */
             int     haddrtype;     /* host address type */
             int     hlength;       /* length of address */
             char    **haddrlist;  /* list of addresses from name server */
     };
     #define haddr  haddrlist[0]  /* address, for backward compatibility */

     The members of this structure are:

     hname       Official name of the host.

     haliases    A NULL-terminated array of alternate names for the host.

     haddrtype   The type of address being returned; usually AFINET.

     hlength     The length, in bytes, of the address.

     haddrlist  A NULL-terminated array of network addresses for the host.
                  Host addresses are returned in network byte order.

     haddr       The first address in haddrlist; this is for backward com-
                  patibility.

     When using the nameserver, ggeetthhoossttbbyynnaammee() and ggeetthhoossttbbyynnaammee22() will
     search for the named host in the current domain and its parents unless
     the name ends in a dot.  If the name contains no dot, and if the environ-
     ment variable ``HOSTALIASES'' contains the name of an alias file, the
     alias file will first be searched for an alias matching the input name.
     See hostname(7) for the domain search procedure and the alias file for-
     mat.

     The ggeetthhoossttbbyynnaammee22() function is an evolution of ggeetthhoossttbbyynnaammee() which is
     intended to allow lookups in address families other than AFINET, for
     example AFINET6.  Both of these address families are supported in the
     Mac OS X implemention.

     The sseetthhoosstteenntt() function may be used to request the use of a connected
     TCP socket for queries.  If the stayopen flag is non-zero, this sets the
     option to send all queries to the name server using TCP and to retain the
     connection after each call to ggeetthhoossttbbyynnaammee(), ggeetthhoossttbbyynnaammee22() or
     ggeetthhoossttbbyyaaddddrr().  Otherwise, queries are performed using UDP datagrams.

     The eennddhhoosstteenntt() function closes the TCP connection.

     The hheerrrroorr() function writes a message to the diagnostic output consist-
     ing of the string parameter s, the constant string ": ", and a message
     corresponding to the value of herrno.

     The hhssttrreerrrroorr() function returns a string which is the message text cor-
     responding to the value of the err parameter.

FILES     /etc/hosts
     /etc/host.conf
     /etc/resolv.conf

DIAGNOSTICS     Error return status from ggeetthhoossttbbyynnaammee(), ggeetthhoossttbbyynnaammee22() and
     ggeetthhoossttbbyyaaddddrr() is indicated by return of a NULL pointer.  The external
     integer herrno may then be checked to see whether this is a temporary
     failure or an invalid or unknown host.  The routine hheerrrroorr() can be used
     to print an error message describing the failure.  If its argument string
     is non-NULL, it is printed, followed by a colon and a space.  The error
     message is printed with a trailing newline.

     The variable herrno can have the following values:

     HOSTNOTFOUND  No such host is known.

     TRYAGAIN       This is usually a temporary error and means that the
                     local server did not receive a response from an authori-
                     tative server.  A retry at some later time may succeed.

     NORECOVERY     Some unexpected server failure was encountered.  This is
                     a non-recoverable error.

     NODATA         The requested name is valid but does not have an IP
                     address; this is not a temporary error.  This means that
                     the name is known to the name server but there is no
                     address associated with this name.  Another type of
                     request to the name server using this domain name will
                     result in an answer; for example, a mail-forwarder may be
                     registered for this domain.

SEE ALSO
     getaddrinfo(3), resolver(3), hosts(5), hostname(7), named(8)

CCAAVVEEAATT
     The ggeetthhoosstteenntt() function is defined, and sseetthhoosstteenntt() and eennddhhoosstteenntt()
     are redefined, when libc is built to use only the routines to lookup in
     /etc/hosts and not the name server.

     The ggeetthhoosstteenntt() function reads the next line of /etc/hosts, opening the
     file if necessary.

     The sseetthhoosstteenntt() function opens and/or rewinds the file /etc/hosts.  If
     the stayopen argument is non-zero, the file will not be closed after each
     call to ggeetthhoossttbbyynnaammee(), ggeetthhoossttbbyynnaammee22() or ggeetthhoossttbbyyaaddddrr().

     The eennddhhoosstteenntt() function closes the file.

HISTORY     The hheerrrroorr() function appeared in 4.3BSD.  The eennddhhoosstteenntt(),
     ggeetthhoossttbbyyaaddddrr(), ggeetthhoossttbbyynnaammee(), ggeetthhoosstteenntt(), and sseetthhoosstteenntt() func-
     tions appeared in 4.2BSD.  The ggeetthhoossttbbyynnaammee22() function first appeared
     in BIND version 4.9.4.

BUGS
     These functions use static data storage; if the data is needed for future
     use, it should be copied before any subsequent calls overwrite it.  Only
     the Internet address format is currently understood.

BSD                              May 25, 1995                              BSD