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getservbyname(3c)

Standard C Library Functions                                 getservbyname(3C)



NAME
       getservbyname, getservbyname_r, getservbyport, getservbyport_r, getser‐
       vent, getservent_r, setservent, endservent - get service entry

SYNOPSIS
       #include <netdb.h>

       struct servent *getservbyname(const char *name, const char *proto);


       struct servent *getservbyname_r(const char *name, const char *proto,
            struct servent *result, char *buffer, int buflen);


       struct servent *getservbyport(int port, const char *proto);


       struct servent *getservbyport_r(int port, const char *proto,
            struct servent *result, char *buffer, int buflen);


       struct servent *getservent(void);


       struct servent *getservent_r(struct servent *result, char *buffer,
            int buflen);


       int setservent(int stayopen);


       int endservent(void);

DESCRIPTION
       These functions are used to obtain entries for  Internet  services.  An
       entry  may  come  from any of the sources for services specified in the
       /etc/nsswitch.conf file. See nsswitch.conf(5).


       The getservbyname() and getservbyport() functions  sequentially  search
       from  the  beginning of the file until a matching protocol name or port
       number is found, or until end-of-file is  encountered.  If  a  protocol
       name  is  also supplied (non-null), searches must also match the proto‐
       col.


       The getservbyname() function searches for an entry  with  the  Internet
       service name specified by the name parameter.


       The  getservbyport()  function  searches for an entry with the Internet
       port number port.


       All addresses are returned in network order. In order to interpret  the
       addresses,  byteorder(3C)  must  be used for byte order conversion. The
       string proto is used by both  getservbyname()  and  getservbyport()  to
       restrict the search to entries with the specified protocol. If proto is
       NULL, entries with any protocol can be returned.


       The functions setservent(), getservent(), and endservent() are used  to
       enumerate entries from the services database.


       The  setservent()  function  sets  (or  resets)  the enumeration to the
       beginning of the set of service entries. This function should be called
       before  the  first  call  to  getservent(). Calls to the functions get‐
       servbyname() and getservbyport() leave the enumeration position  in  an
       indeterminate  state.  If the stayopen flag is non-zero, the system may
       keep allocated resources such as open file descriptors until  a  subse‐
       quent call to endservent().


       The  getservent() function reads the next line of the file, opening the
       file if necessary. getservent() opens and  rewinds  the  file.  If  the
       stayopen  flag  is non-zero, the net data base will not be closed after
       each call to getservent() (either directly, or indirectly  through  one
       of the other "getserv"calls).


       Successive  calls  to  getservent() return either successive entries or
       NULL, indicating the end of the enumeration.


       The endservent() function closes the file.  The  endservent()  function
       can be called to indicate that the caller expects to do no further ser‐
       vice  entry  retrieval  operations;  the  system  can  then  deallocate
       resources  it  was  using. It is still allowed, but possibly less effi‐
       cient, for the process to call more service entry  retrieval  functions
       after calling endservent().

   Reentrant Interfaces
       The  functions  getservbyname(),  getservbyport(), and getservent() use
       static storage that is re-used in each  call,  making  these  functions
       unsafe for use in multithreaded applications.


       The  functions getservbyname_r(), getservbyport_r(), and getservent_r()
       provide reentrant interfaces for these operations.


       Each reentrant interface performs the same operation as  its  non-reen‐
       trant  counterpart,  named  by  removing the "_r" suffix. The reentrant
       interfaces, however, use  buffers  supplied  by  the  caller  to  store
       returned results, and are safe for use in both single-threaded and mul‐
       tithreaded applications.


       Each reentrant interface takes the same parameters as its non-reentrant
       counterpart, as well as the following additional parameters. The param‐
       eter result must be a pointer to a struct servent  structure  allocated
       by  the caller. On successful completion, the function returns the ser‐
       vice entry in this structure. The parameter buffer must be a pointer to
       a  buffer  supplied by the caller. This buffer is used as storage space
       for the service entry data. All of the  pointers  within  the  returned
       struct servent  result point to data stored within this buffer. See the
       RETURN VALUES section of this manual page. The  buffer  must  be  large
       enough  to  hold all of the data associated with the service entry. The
       parameter buflen should give the size in bytes of the buffer  indicated
       by buffer.


       For  enumeration in multithreaded applications, the position within the
       enumeration is a process-wide property shared by all threads. The  set‐
       servent()  function  can  be  used  in  a multithreaded application but
       resets the enumeration position for all threads.  If  multiple  threads
       interleave calls to getservent_r(), the threads will enumerate disjoint
       subsets of the service database.


       Like their non-reentrant counterparts, getservbyname_r() and getservby‐
       port_r() leave the enumeration position in an indeterminate state.

RETURN VALUES
       Service entries are represented by the struct servent structure defined
       in <netdb.h>:

         struct  servent {
             char  *s_name;             /* official name of service */
             char  **s_aliases;           /* alias list */
             int   s_port;                /* port service resides at */
             char  *s_proto;            /* protocol to use */
         };



       The members of this structure are:

       s_name       The official name of the service.


       s_aliases    A zero terminated list of alternate names for the service.


       s_port       The port number at which the service resides. Port numbers
                    are returned in network byte order.


       s_proto      The  name  of the protocol to use when contacting the ser‐
                    vice



       The functions getservbyname(), getservbyname_r(), getservbyport(),  and
       getservbyport_r()  each  return  a  pointer to a struct servent if they
       successfully locate the requested entry; otherwise they return NULL.


       The functions getservent() and getservent_r() each return a pointer  to
       a  struct  servent  if  they successfully enumerate an entry; otherwise
       they return NULL, indicating the end of the enumeration.


       The functions getservbyname(), getservbyport(),  and  getservent()  use
       static  storage,  so  returned  data must be copied before a subsequent
       call to any of these functions if the data is to be saved.


       When the pointer returned by the reentrant functions getservbyname_r(),
       getservbyport_r(),  and  getservent_r() is non-null, it is always equal
       to the result pointer that was supplied by the caller.

ERRORS
       The reentrant functions getservbyname_r(), getservbyport_r(), and  get‐
       servent_r()  return  NULL  and set errno to ERANGE if the length of the
       buffer supplied by caller is not large enough to store the result.  See
       Intro(2)  for  the  proper  usage and interpretation of errno in multi‐
       threaded applications.

FILES
       /etc/services         Internet network services


       /etc/netconfig        network configuration file


       /etc/nsswitch.conf    configuration file for the name-service switch


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE  VALUE  _ MT-LevelT{ See "Reentrant Interfaces" in DESCRIPTION.
       T}


SEE ALSO
       Intro(2), byteorder(3C), netdir(3C), netdb.h(3HEAD),  nsswitch.conf(5),
       netconfig(5), services(5), attributes(7)

WARNINGS
       The reentrant interfaces getservbyname_r(), getservbyport_r(), and get‐
       servent_r() are included in this release on an uncommitted basis  only,
       and are subject to change or removal in future minor releases.

NOTES
       The  functions  that return struct servent return the least significant
       16-bits of the s_port field in network byte order. getservbyport()  and
       getservbyport_r()  also  expect the input parameter port in the network
       byte order. See htons(3C) for more details on converting  between  host
       and network byte orders.


       To  ensure  that  they  all return consistent results, getservbyname(),
       getservbyname_r(), and netdir_getbyname() are implemented in  terms  of
       the  same  internal library function. This function obtains the system-
       wide source lookup policy based on the inet family entries  in  netcon‐
       fig(5)  and  the  services:  entry in nsswitch.conf(5). Similarly, get‐
       servbyport(), getservbyport_r(), and netdir_getbyaddr() are implemented
       in  terms  of  the  same  internal library function. If the inet family
       entries in netconfig(5) have a ``-'' in the last column for  nametoaddr
       libraries,  then  the entry for services in nsswitch.conf will be used;
       otherwise the nametoaddr libraries in that column  will  be  used,  and
       nsswitch.conf will not be consulted.


       There  is  no analogue of getservent() and getservent_r() in the netdir
       functions, so these enumeration functions go straight to  the  services
       entry in nsswitch.conf. Thus enumeration may return results from a dif‐
       ferent source than that  used  by  getservbyname(),  getservbyname_r(),
       getservbyport(), and getservbyport_r().


       Use  of  the  enumeration interfaces getservent() and getservent_r() is
       discouraged; enumeration may not be supported for all database sources.
       The semantics of enumeration are discussed further in nsswitch.conf(5).



Oracle Solaris 11.4               19 May 2014                getservbyname(3C)
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