1GETPROTOENT_R(3)           Linux Programmer's Manual          GETPROTOENT_R(3)
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NAME

6       getprotoent_r,  getprotobyname_r,  getprotobynumber_r  -  get  protocol
7       entry (reentrant)
8

SYNOPSIS

10       #include <netdb.h>
11
12       int getprotoent_r(struct protoent *result_buf, char *buf,
13                       size_t buflen, struct protoent **result);
14
15       int getprotobyname_r(const char *name,
16                       struct protoent *result_buf, char *buf,
17                       size_t buflen, struct protoent **result);
18
19       int getprotobynumber_r(int proto,
20                       struct protoent *result_buf, char *buf,
21                       size_t buflen, struct protoent **result);
22
23   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
24
25       getprotoent_r(), getprotobyname_r(), getprotobynumber_r():
26           _BSD_SOURCE || _SVID_SOURCE
27

DESCRIPTION

29       The getprotoent_r(), getprotobyname_r(), and getprotobynumber_r() func‐
30       tions  are  the reentrant equivalents of, respectively, getprotoent(3),
31       getprotobyname(3), and getprotobynumber(3).  They  differ  in  the  way
32       that  the  protoent  structure is returned, and in the function calling
33       signature and return value.  This manual page describes just  the  dif‐
34       ferences from the nonreentrant functions.
35
36       Instead  of  returning  a  pointer  to  a statically allocated protoent
37       structure as the function result, these functions  copy  the  structure
38       into the location pointed to by result_buf.
39
40       The  buf  array  is  used  to store the string fields pointed to by the
41       returned protoent  structure.   (The  nonreentrant  functions  allocate
42       these  strings in static storage.)  The size of this array is specified
43       in buflen.  If buf is too small, the call fails with the error  ERANGE,
44       and  the  caller  must  try  again  with a larger buffer.  (A buffer of
45       length 1024 bytes should be sufficient for most applications.)
46
47       If the function call  successfully  obtains  a  protocol  record,  then
48       *result  is  set  pointing  to result_buf; otherwise, *result is set to
49       NULL.
50

RETURN VALUE

52       On success, these functions return 0.  On error, they return one of the
53       positive error numbers listed in ERRORS.
54
55       On  error, record not found (getprotobyname_r(), getprotobynumber_r()),
56       or end of input (getprotoent_r()) result is set to NULL.
57

ERRORS

59       ENOENT (getprotoent_r()) No more records in database.
60
61       ERANGE buf is too small.  Try again with a larger buffer (and increased
62              buflen).
63

CONFORMING TO

65       These functions are GNU extensions.  Functions with similar names exist
66       on some other systems, though typically with different  calling  signa‐
67       tures.
68

EXAMPLE

70       The  program  below  uses  getprotobyname_r()  to retrieve the protocol
71       record for the protocol named in its first command-line argument.  If a
72       second  (integer)  command-line argument is supplied, it is used as the
73       initial value for buflen; if getprotobyname_r() fails  with  the  error
74       ERANGE,  the  program  retries with larger buffer sizes.  The following
75       shell session shows a couple of sample runs:
76
77           $ ./a.out tcp 1
78           ERANGE! Retrying with larger buffer
79           getprotobyname_r() returned: 0 (success)  (buflen=78)
80           p_name=tcp; p_proto=6; aliases=TCP
81           $ ./a.out xxx 1
82           ERANGE! Retrying with larger buffer
83           getprotobyname_r() returned: 0 (success)  (buflen=100)
84           Call failed/record not found
85
86   Program source
87
88       #define _GNU_SOURCE
89       #include <ctype.h>
90       #include <netdb.h>
91       #include <stdlib.h>
92       #include <stdio.h>
93       #include <errno.h>
94       #include <string.h>
95
96       #define MAX_BUF 10000
97
98       int
99       main(int argc, char *argv[])
100       {
101           int buflen, erange_cnt, s;
102           struct protoent result_buf;
103           struct protoent *result;
104           char buf[MAX_BUF];
105           char **p;
106
107           if (argc < 2) {
108               printf("Usage: %s proto-name [buflen]\n", argv[0]);
109               exit(EXIT_FAILURE);
110           }
111
112           buflen = 1024;
113           if (argc > 2)
114               buflen = atoi(argv[2]);
115
116           if (buflen > MAX_BUF) {
117               printf("Exceeded buffer limit (%d)\n", MAX_BUF);
118               exit(EXIT_FAILURE);
119           }
120
121           erange_cnt = 0;
122           do {
123               s = getprotobyname_r(argv[1], &result_buf,
124                            buf, buflen, &result);
125               if (s == ERANGE) {
126                   if (erange_cnt == 0)
127                       printf("ERANGE! Retrying with larger buffer\n");
128                   erange_cnt++;
129
130                   /* Increment a byte at a time so we can see exactly
131                      what size buffer was required */
132
133                   buflen++;
134
135                   if (buflen > MAX_BUF) {
136                       printf("Exceeded buffer limit (%d)\n", MAX_BUF);
137                       exit(EXIT_FAILURE);
138                   }
139               }
140           } while (s == ERANGE);
141
142           printf("getprotobyname_r() returned: %s  (buflen=%d)\n",
143                   (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
144                   strerror(s), buflen);
145
146           if (s != 0 || result == NULL) {
147               printf("Call failed/record not found\n");
148               exit(EXIT_FAILURE);
149           }
150
151           printf("p_name=%s; p_proto=%d; aliases=",
152                       result_buf.p_name, result_buf.p_proto);
153           for (p = result_buf.p_aliases; *p != NULL; p++)
154               printf("%s ", *p);
155           printf("\n");
156
157           exit(EXIT_SUCCESS);
158       }
159

SEE ALSO

161       getprotoent(3), protocols(5)
162

COLOPHON

164       This page is part of release 3.53 of the Linux  man-pages  project.   A
165       description  of  the project, and information about reporting bugs, can
166       be found at http://www.kernel.org/doc/man-pages/.
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170GNU                               2010-09-10                  GETPROTOENT_R(3)
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