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

       endprotoent, getprotobyname, getprotobynumber, getprotoent, setprotoent — network protocol
       database functions

SYNOPSIS

       #include <netdb.h>

       void endprotoent(void);
       struct protoent *getprotobyname(const char *name);
       struct protoent *getprotobynumber(int proto);
       struct protoent *getprotoent(void);
       void setprotoent(int stayopen);

DESCRIPTION

       These functions shall retrieve information about protocols. 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 setprotoent() 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 connection to the network
       protocol database shall not be closed after each call to getprotoent()  (either  directly,
       or  indirectly through one of the other getproto*() functions), and the implementation may
       maintain an open file descriptor for the database.

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

       The getprotobynumber() function shall search the database from the beginning and find  the
       first  entry  for which the protocol number specified by proto matches the p_proto member,
       opening and closing a connection to the database as necessary.

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

       The  getprotobyname(), getprotobynumber(), and getprotoent() functions shall each return a
       pointer to a protoent structure, the members of which shall contain the fields of an entry
       in the network protocol database.

       The  endprotoent() function shall close the connection to the database, releasing any open
       file descriptor.

       These functions need not be thread-safe.

RETURN VALUE

       Upon successful completion, getprotobyname(), getprotobynumber(), and getprotoent() return
       a  pointer to a protoent 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  getprotobyname(),  getprotobynumber(),  or
       getprotoent().

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.1‐2008, <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 .