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

       endservent, getservbyname, getservbyport, getservent, setservent — network services database functions

SYNOPSIS

       #include <netdb.h>

       void endservent(void);
       struct servent *getservbyname(const char *name, const char *proto);
       struct servent *getservbyport(int port, const char *proto);
       struct servent *getservent(void);
       void setservent(int stayopen);

DESCRIPTION

       These  functions  shall retrieve information about network services. 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  setservent()  function  shall open a connection to the database, and set the next entry to the first
       entry. If the stayopen argument is non-zero, the net database shall not be closed after each call to  the
       getservent() function (either directly, or indirectly through one of the other getserv*() functions), and
       the implementation may maintain an open file descriptor for the database.

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

       The getservbyname() function shall search the database from the beginning and find the  first  entry  for
       which  the  service  name  specified by name matches the s_name member and the protocol name specified by
       proto matches the s_proto member, opening and closing a connection to  the  database  as  necessary.   If
       proto is a null pointer, any value of the s_proto member shall be matched.

       The  getservbyport()  function  shall search the database from the beginning and find the first entry for
       which the port specified by port matches the s_port member and  the  protocol  name  specified  by  proto
       matches the s_proto member, opening and closing a connection to the database as necessary.  If proto is a
       null  pointer,  any  value  of  the  s_proto  member shall be matched. The port argument shall be a value
       obtained by converting a uint16_t in network byte order to int.

       The getservbyname(), getservbyport(), and getservent() functions shall each return a pointer to a servent
       structure, the members of which shall contain the fields of an entry in the network services database.

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

       These functions need not be thread-safe.

RETURN VALUE

       Upon successful completion, getservbyname(), getservbyport(), and getservent()  return  a  pointer  to  a
       servent  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 is 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
       getservbyname(),  getservbyport(),  or  getservent().   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

       The port argument of getservbyport() need not be compatible with the port values of all address families.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       endhostent(), endprotoent(), htonl(), inet_addr()

       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 .

IEEE/The Open Group                                   2017                                    ENDSERVENT(3POSIX)