PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       endnetent, getnetbyaddr, getnetbyname, getnetent, setnetent — network database functions

SYNOPSIS

       #include <netdb.h>

       void endnetent(void);
       struct netent *getnetbyaddr(uint32_t net, int type);
       struct netent *getnetbyname(const char *name);
       struct netent *getnetent(void);
       void setnetent(int stayopen);

DESCRIPTION

       These  functions shall retrieve information about networks. This information is considered
       to  be  stored  in  a  database  that  can  be  accessed  sequentially  or  randomly.  The
       implementation of this database is unspecified.

       The  setnetent()  function shall open and rewind the database. If the stayopen argument is
       non-zero, the connection to the net database shall  not  be  closed  after  each  call  to
       getnetent() (either directly, or indirectly through one of the other getnet*() functions),
       and the implementation may maintain an open file descriptor to the database.

       The getnetent() function shall read the next entry of the database, opening and closing  a
       connection to the database as necessary.

       The  getnetbyaddr()  function  shall  search the database from the beginning, and find the
       first entry for which the address family specified by type matches the  n_addrtype  member
       and  the  network number net matches the n_net member, opening and closing a connection to
       the database as necessary.  The net argument shall be the  network  number  in  host  byte
       order.

       The  getnetbyname()  function  shall  search  the database from the beginning and find the
       first entry for which the network name  specified  by  name  matches  the  n_name  member,
       opening and closing a connection to the database as necessary.

       The  getnetbyaddr(), getnetbyname(), and getnetent() functions shall each return a pointer
       to a netent structure, the members of which shall contain the fields of an  entry  in  the
       network database.

       The endnetent() function shall close the database, releasing any open file descriptor.

       These functions need not be thread-safe.

RETURN VALUE

       Upon successful completion, getnetbyaddr(), getnetbyname(), and getnetent() shall return a
       pointer to a netent structure if the requested entry was found, and a null pointer if  the
       end  of  the database was reached or the requested entry was not found.  Otherwise, a null
       pointer shall be returned.

       The application shall not modify the structure to which the return value points,  nor  any
       storage  areas  pointed  to  by  pointers  within the structure. The returned pointer, and
       pointers within the structure, might be invalidated or the structure or the storage  areas
       might   be  overwritten  by  a  subsequent  call  to  getnetbyaddr(),  getnetbyname(),  or
       getnetent().  The returned pointer, and pointers  within  the  structure,  might  also  be
       invalidated if the calling thread is terminated.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       The Base Definitions volume of POSIX.1‐2017, <netdb.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1-2017, Standard for Information Technology -- Portable  Operating  System  Interface
       (POSIX),  The  Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
       the Institute of Electrical and Electronics Engineers, Inc and The  Open  Group.   In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
       been introduced during the conversion of the source files to man page  format.  To  report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .