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);
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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)):
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25       getprotoent_r(), getprotobyname_r(), getprotobynumber_r(): _BSD_SOURCE
26       || _SVID_SOURCE
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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.)
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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.
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RETURN VALUE

52       On  success, these functions return 0.  On error, a positive error num‐
53       ber is returned.
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55       On error, record not found (getprotobyname_r(),  getprotobynumber_r()),
56       or end of input (getprotoent_r()) result is set to NULL.
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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).
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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 3.25 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                               2008-08-19                  GETPROTOENT_R(3)
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