Man Pages

getservent_r(3) - phpMan getservent_r(3) - phpMan

Command: man perldoc info search(apropos)  


GETSERVENT_R(3)            Linux Programmer's Manual           GETSERVENT_R(3)



NAME
       getservent_r, getservbyname_r, getservbyport_r - get service entry (reentrant)

SYNOPSIS
       #include <netdb.h>

       int getservent_r(struct servent *result_buf, char *buf,
                       size_t buflen, struct servent **result);

       int getservbyname_r(const char *name, const char *proto,
                       struct servent *result_buf, char *buf,
                       size_t buflen, struct servent **result);

       int getservbyport_r(int port, const char *proto,
                       struct servent *result_buf, char *buf,
                       size_t buflen, struct servent **result);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getservent_r(), getservbyname_r(), getservbyport_r(): _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       The  getservent_r(),  getservbyname_r(),  and  getservbyport_r()  functions  are  the reentrant equivalents of,
       respectively, getservent(3), getservbyname(3), and getservbyport(3).  They differ in the way that  the  servent
       structure is returned, and in the function calling signature and return value.  This manual page describes just
       the differences from the non-reentrant functions.

       Instead of returning a pointer to a statically allocated servent structure as the function result, these  func-
       tions copy the structure into the location pointed to by result_buf.

       The  buf array is used to store the string fields pointed to by the returned servent structure.  (The non-reen-
       trant functions allocate these strings in static storage.)  The size of this array is specified in buflen.   If
       buf is too small, the call fails with the error ERANGE, and the caller must try again with a larger buffer.  (A
       buffer of length 1024 bytes should be sufficient for most applications.)

       If the function call successfully obtains a service record, then *result is set pointing to result_buf;  other-
       wise, *result is set to NULL.

RETURN VALUE
       On success, these functions return 0.  On error, a positive error number is returned.

       On  error,  record not found (getservbyname_r(), getservbyport_r()), or end of input (getservent_r()) result is
       set to NULL.

ERRORS
       ENOENT (getservent_r()) No more records in database.

       ERANGE buf is too small.  Try again with a larger buffer (and increased buflen).

CONFORMING TO
       These functions are GNU extensions.  Functions with similar names exist on some other systems, though typically
       with different calling signatures.

EXAMPLE
       The  program below uses getservbyport_r() to retrieve the service record for the port and protocol named in its
       first command-line argument.  If a third (integer) command-line argument is supplied, it is used as the initial
       value  for  buflen;  if  getservbyport_r()  fails with the error ERANGE, the program retries with larger buffer
       sizes.  The following shell session shows a couple of sample runs:

           $ ./a.out 7 tcp 1
           ERANGE! Retrying with larger buffer
           getservbyport_r() returned: 0 (success)  (buflen=87)
           s_name=echo; s_proto=tcp; s_port=7; aliases=
           $ ./a.out 77777 tcp
           getservbyport_r() returned: 0 (success)  (buflen=1024)
           Call failed/record not found

   Program source

       #define _GNU_SOURCE
       #include <ctype.h>
       #include <netdb.h>
       #include <stdlib.h>
       #include <stdio.h>
       #include <errno.h>
       #include <string.h>

       #define MAX_BUF 10000

       int
       main(int argc, char *argv[])
       {
           int buflen, erange_cnt, port, s;
           struct servent result_buf;
           struct servent *result;
           char buf[MAX_BUF];
           char *protop;
           char **p;

           if (argc < 3) {
               printf("Usage: %s port-num proto-name [buflen]\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           port = htons(atoi(argv[1]));
           protop = (strcmp(argv[2], "null") == 0 ||
                  strcmp(argv[2], "NULL") == 0) ?  NULL : argv[2];

           buflen = 1024;
           if (argc > 3)
               buflen = atoi(argv[3]);

           if (buflen > MAX_BUF) {
               printf("Exceeded buffer limit (%d)\n", MAX_BUF);
               exit(EXIT_FAILURE);
           }

           erange_cnt = 0;
           do {
               s = getservbyport_r(port, protop, &result_buf,
                            buf, buflen, &result);
               if (s == ERANGE) {
                   if (erange_cnt == 0)
                       printf("ERANGE! Retrying with larger buffer\n");
                   erange_cnt++;

                   /* Increment a byte at a time so we can see exactly
                      what size buffer was required */

                   buflen++;

                   if (buflen > MAX_BUF) {
                       printf("Exceeded buffer limit (%d)\n", MAX_BUF);
                       exit(EXIT_FAILURE);
                   }
               }
           } while (s == ERANGE);

           printf("getservbyport_r() returned: %s  (buflen=%d)\n",
                   (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
                   strerror(s), buflen);

           if (s != 0 || result == NULL) {
               printf("Call failed/record not found\n");
               exit(EXIT_FAILURE);
           }

           printf("s_name=%s; s_proto=%s; s_port=%d; aliases=",
                       result_buf.s_name, result_buf.s_proto,
                       ntohs(result_buf.s_port));
           for (p = result_buf.s_aliases; *p != NULL; p++)
               printf("%s ", *p);
           printf("\n");

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       getservent(3), services(5)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2008-08-19                   GETSERVENT_R(3)