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1 | .\" Copyright 2008, Linux Foundation, written by Michael Kerrisk |
2 | .\" <mtk.manpages@gmail.com> | |
3 | .\" | |
93015253 | 4 | .\" %%%LICENSE_START(VERBATIM) |
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5 | .\" Permission is granted to make and distribute verbatim copies of this |
6 | .\" manual provided the copyright notice and this permission notice are | |
7 | .\" preserved on all copies. | |
8 | .\" | |
9 | .\" Permission is granted to copy and distribute modified versions of this | |
10 | .\" manual under the conditions for verbatim copying, provided that the | |
11 | .\" entire resulting derived work is distributed under the terms of a | |
12 | .\" permission notice identical to this one. | |
13 | .\" | |
14 | .\" Since the Linux kernel and libraries are constantly changing, this | |
15 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
16 | .\" responsibility for errors or omissions, or for damages resulting from | |
17 | .\" the use of the information contained herein. The author(s) may not | |
18 | .\" have taken the same level of care in the production of this manual, | |
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20 | .\" professionally. | |
21 | .\" | |
22 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
23 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 24 | .\" %%%LICENSE_END |
1280fbc6 | 25 | .\" |
4b8c67d9 | 26 | .TH GETSERVENT_R 3 2017-09-15 "GNU" "Linux Programmer's Manual" |
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27 | .SH NAME |
28 | getservent_r, getservbyname_r, getservbyport_r \- get | |
29 | service entry (reentrant) | |
30 | .SH SYNOPSIS | |
31 | .nf | |
32 | .B #include <netdb.h> | |
68e4db0a | 33 | .PP |
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34 | .BI "int getservent_r(struct servent *" result_buf ", char *" buf , |
35 | .BI " size_t " buflen ", struct servent **" result ); | |
68e4db0a | 36 | .PP |
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37 | .BI "int getservbyname_r(const char *" name ", const char *" proto , |
38 | .BI " struct servent *" result_buf ", char *" buf , | |
39 | .BI " size_t " buflen ", struct servent **" result ); | |
68e4db0a | 40 | .PP |
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41 | .BI "int getservbyport_r(int " port ", const char *" proto , |
42 | .BI " struct servent *" result_buf ", char *" buf , | |
43 | .BI " size_t " buflen ", struct servent **" result ); | |
68e4db0a | 44 | .PP |
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45 | .fi |
46 | .in -4n | |
47 | Feature Test Macro Requirements for glibc (see | |
48 | .BR feature_test_macros (7)): | |
49 | .ad l | |
50 | .in | |
68e4db0a | 51 | .PP |
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52 | .BR getservent_r (), |
53 | .BR getservbyname_r (), | |
54 | .BR getservbyport_r (): | |
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55 | Since glibc 2.19: |
56 | _DEFAULT_SOURCE | |
57 | Glibc 2.19 and earlier: | |
58 | _BSD_SOURCE || _SVID_SOURCE | |
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59 | .ad b |
60 | .SH DESCRIPTION | |
61 | The | |
62 | .BR getservent_r (), | |
63 | .BR getservbyname_r (), | |
64 | and | |
65 | .BR getservbyport_r () | |
66 | functions are the reentrant equivalents of, respectively, | |
67 | .BR getservent (3), | |
68 | .BR getservbyname (3), | |
69 | and | |
70 | .BR getservbyport (3). | |
71 | They differ in the way that the | |
72 | .I servent | |
73 | structure is returned, | |
74 | and in the function calling signature and return value. | |
75 | This manual page describes just the differences from | |
54d75d6c | 76 | the nonreentrant functions. |
847e0d88 | 77 | .PP |
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78 | Instead of returning a pointer to a statically allocated |
79 | .I servent | |
80 | structure as the function result, | |
81 | these functions copy the structure into the location pointed to by | |
82 | .IR result_buf . | |
847e0d88 | 83 | .PP |
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84 | The |
85 | .I buf | |
86 | array is used to store the string fields pointed to by the returned | |
87 | .I servent | |
88 | structure. | |
54d75d6c | 89 | (The nonreentrant functions allocate these strings in static storage.) |
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90 | The size of this array is specified in |
91 | .IR buflen . | |
92 | If | |
93 | .I buf | |
94 | is too small, the call fails with the error | |
95 | .BR ERANGE , | |
96 | and the caller must try again with a larger buffer. | |
97 | (A buffer of length 1024 bytes should be sufficient for most applications.) | |
98 | .\" I can find no information on the required/recommended buffer size; | |
54d75d6c | 99 | .\" the nonreentrant functions use a 1024 byte buffer -- mtk. |
847e0d88 | 100 | .PP |
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101 | If the function call successfully obtains a service record, then |
102 | .I *result | |
103 | is set pointing to | |
104 | .IR result_buf ; | |
105 | otherwise, | |
106 | .I *result | |
107 | is set to NULL. | |
47297adb | 108 | .SH RETURN VALUE |
1280fbc6 | 109 | On success, these functions return 0. |
535f0df5 | 110 | On error, they return one of the positive error numbers listed in errors. |
847e0d88 | 111 | .PP |
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112 | On error, record not found |
113 | .RB ( getservbyname_r (), | |
114 | .BR getservbyport_r ()), | |
115 | or end of input | |
116 | .RB ( getservent_r ()) | |
117 | .I result | |
118 | is set to NULL. | |
119 | .SH ERRORS | |
120 | .TP | |
121 | .B ENOENT | |
122 | .RB ( getservent_r ()) | |
123 | No more records in database. | |
124 | .TP | |
125 | .B ERANGE | |
126 | .I buf | |
127 | is too small. | |
128 | Try again with a larger buffer | |
129 | (and increased | |
130 | .IR buflen ). | |
67e569aa ZL |
131 | .SH ATTRIBUTES |
132 | For an explanation of the terms used in this section, see | |
133 | .BR attributes (7). | |
74714ea8 | 134 | .ad l |
67e569aa ZL |
135 | .TS |
136 | allbox; | |
137 | lbw18 lb lb | |
138 | l l l. | |
139 | Interface Attribute Value | |
140 | T{ | |
141 | .BR getservent_r (), | |
142 | .BR getservbyname_r (), | |
143 | .BR getservbyport_r () | |
144 | T} Thread safety MT-Safe locale | |
145 | .TE | |
74714ea8 | 146 | .ad |
47297adb | 147 | .SH CONFORMING TO |
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148 | These functions are GNU extensions. |
149 | Functions with similar names exist on some other systems, | |
150 | though typically with different calling signatures. | |
151 | .SH EXAMPLE | |
152 | The program below uses | |
153 | .BR getservbyport_r () | |
154 | to retrieve the service record for the port and protocol named | |
155 | in its first command-line argument. | |
156 | If a third (integer) command-line argument is supplied, | |
157 | it is used as the initial value for | |
158 | .IR buflen ; | |
159 | if | |
160 | .BR getservbyport_r () | |
161 | fails with the error | |
162 | .BR ERANGE , | |
163 | the program retries with larger buffer sizes. | |
164 | The following shell session shows a couple of sample runs: | |
e646a1ba | 165 | .PP |
1280fbc6 | 166 | .in +4n |
e646a1ba | 167 | .EX |
b43a3b30 | 168 | .RB "$" " ./a.out 7 tcp 1" |
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169 | ERANGE! Retrying with larger buffer |
170 | getservbyport_r() returned: 0 (success) (buflen=87) | |
171 | s_name=echo; s_proto=tcp; s_port=7; aliases= | |
b43a3b30 | 172 | .RB "$" " ./a.out 77777 tcp" |
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173 | getservbyport_r() returned: 0 (success) (buflen=1024) |
174 | Call failed/record not found | |
b8302363 | 175 | .EE |
1280fbc6 | 176 | .in |
9c330504 | 177 | .SS Program source |
d84d0300 | 178 | \& |
e7d0bb47 | 179 | .EX |
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180 | #define _GNU_SOURCE |
181 | #include <ctype.h> | |
182 | #include <netdb.h> | |
183 | #include <stdlib.h> | |
184 | #include <stdio.h> | |
185 | #include <errno.h> | |
186 | #include <string.h> | |
187 | ||
188 | #define MAX_BUF 10000 | |
189 | ||
190 | int | |
191 | main(int argc, char *argv[]) | |
192 | { | |
193 | int buflen, erange_cnt, port, s; | |
194 | struct servent result_buf; | |
195 | struct servent *result; | |
196 | char buf[MAX_BUF]; | |
197 | char *protop; | |
198 | char **p; | |
199 | ||
200 | if (argc < 3) { | |
72da9ef1 | 201 | printf("Usage: %s port\-num proto\-name [buflen]\\n", argv[0]); |
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202 | exit(EXIT_FAILURE); |
203 | } | |
204 | ||
205 | port = htons(atoi(argv[1])); | |
206 | protop = (strcmp(argv[2], "null") == 0 || | |
5a6194a4 | 207 | strcmp(argv[2], "NULL") == 0) ? NULL : argv[2]; |
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208 | |
209 | buflen = 1024; | |
210 | if (argc > 3) | |
211 | buflen = atoi(argv[3]); | |
212 | ||
213 | if (buflen > MAX_BUF) { | |
214 | printf("Exceeded buffer limit (%d)\\n", MAX_BUF); | |
215 | exit(EXIT_FAILURE); | |
216 | } | |
217 | ||
218 | erange_cnt = 0; | |
219 | do { | |
220 | s = getservbyport_r(port, protop, &result_buf, | |
221 | buf, buflen, &result); | |
222 | if (s == ERANGE) { | |
223 | if (erange_cnt == 0) | |
224 | printf("ERANGE! Retrying with larger buffer\\n"); | |
225 | erange_cnt++; | |
226 | ||
227 | /* Increment a byte at a time so we can see exactly | |
228 | what size buffer was required */ | |
229 | ||
230 | buflen++; | |
231 | ||
232 | if (buflen > MAX_BUF) { | |
233 | printf("Exceeded buffer limit (%d)\\n", MAX_BUF); | |
234 | exit(EXIT_FAILURE); | |
235 | } | |
236 | } | |
237 | } while (s == ERANGE); | |
238 | ||
239 | printf("getservbyport_r() returned: %s (buflen=%d)\\n", | |
240 | (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" : | |
241 | strerror(s), buflen); | |
242 | ||
243 | if (s != 0 || result == NULL) { | |
244 | printf("Call failed/record not found\\n"); | |
245 | exit(EXIT_FAILURE); | |
246 | } | |
247 | ||
248 | printf("s_name=%s; s_proto=%s; s_port=%d; aliases=", | |
249 | result_buf.s_name, result_buf.s_proto, | |
250 | ntohs(result_buf.s_port)); | |
251 | for (p = result_buf.s_aliases; *p != NULL; p++) | |
252 | printf("%s ", *p); | |
253 | printf("\\n"); | |
254 | ||
255 | exit(EXIT_SUCCESS); | |
256 | } | |
e7d0bb47 | 257 | .EE |
47297adb | 258 | .SH SEE ALSO |
1280fbc6 | 259 | .BR getservent (3), |
1280fbc6 | 260 | .BR services (5) |