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().

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.1‐2008, <netdb.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2013  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013  by  the
       Institute  of  Electrical  and  Electronics  Engineers,  Inc and The Open Group.  (This is
       POSIX.1-2008 with the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .