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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15 | .\" manual page may be incorrect or out-of-date.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, | |
19 | .\" which is licensed free of charge, as they might when working | |
20 | .\" professionally. | |
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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 | .\" |
535f0df5 | 26 | .TH GETSERVENT_R 3 2010-09-10 "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> | |
33 | .sp | |
34 | .BI "int getservent_r(struct servent *" result_buf ", char *" buf , | |
35 | .BI " size_t " buflen ", struct servent **" result ); | |
36 | .sp | |
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 ); | |
40 | .sp | |
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 ); | |
44 | .sp | |
45 | .fi | |
46 | .in -4n | |
47 | Feature Test Macro Requirements for glibc (see | |
48 | .BR feature_test_macros (7)): | |
49 | .ad l | |
50 | .in | |
51 | .sp | |
52 | .BR getservent_r (), | |
53 | .BR getservbyname_r (), | |
54 | .BR getservbyport_r (): | |
684f3f5c | 55 | .RS 4 |
1280fbc6 | 56 | _BSD_SOURCE || _SVID_SOURCE |
684f3f5c | 57 | .RE |
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58 | .ad b |
59 | .SH DESCRIPTION | |
60 | The | |
61 | .BR getservent_r (), | |
62 | .BR getservbyname_r (), | |
63 | and | |
64 | .BR getservbyport_r () | |
65 | functions are the reentrant equivalents of, respectively, | |
66 | .BR getservent (3), | |
67 | .BR getservbyname (3), | |
68 | and | |
69 | .BR getservbyport (3). | |
70 | They differ in the way that the | |
71 | .I servent | |
72 | structure is returned, | |
73 | and in the function calling signature and return value. | |
74 | This manual page describes just the differences from | |
54d75d6c | 75 | the nonreentrant functions. |
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76 | |
77 | Instead of returning a pointer to a statically allocated | |
78 | .I servent | |
79 | structure as the function result, | |
80 | these functions copy the structure into the location pointed to by | |
81 | .IR result_buf . | |
82 | ||
83 | The | |
84 | .I buf | |
85 | array is used to store the string fields pointed to by the returned | |
86 | .I servent | |
87 | structure. | |
54d75d6c | 88 | (The nonreentrant functions allocate these strings in static storage.) |
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89 | The size of this array is specified in |
90 | .IR buflen . | |
91 | If | |
92 | .I buf | |
93 | is too small, the call fails with the error | |
94 | .BR ERANGE , | |
95 | and the caller must try again with a larger buffer. | |
96 | (A buffer of length 1024 bytes should be sufficient for most applications.) | |
97 | .\" I can find no information on the required/recommended buffer size; | |
54d75d6c | 98 | .\" the nonreentrant functions use a 1024 byte buffer -- mtk. |
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99 | |
100 | If the function call successfully obtains a service record, then | |
101 | .I *result | |
102 | is set pointing to | |
103 | .IR result_buf ; | |
104 | otherwise, | |
105 | .I *result | |
106 | is set to NULL. | |
47297adb | 107 | .SH RETURN VALUE |
1280fbc6 | 108 | On success, these functions return 0. |
535f0df5 | 109 | On error, they return one of the positive error numbers listed in errors. |
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110 | |
111 | On error, record not found | |
112 | .RB ( getservbyname_r (), | |
113 | .BR getservbyport_r ()), | |
114 | or end of input | |
115 | .RB ( getservent_r ()) | |
116 | .I result | |
117 | is set to NULL. | |
118 | .SH ERRORS | |
119 | .TP | |
120 | .B ENOENT | |
121 | .RB ( getservent_r ()) | |
122 | No more records in database. | |
123 | .TP | |
124 | .B ERANGE | |
125 | .I buf | |
126 | is too small. | |
127 | Try again with a larger buffer | |
128 | (and increased | |
129 | .IR buflen ). | |
47297adb | 130 | .SH CONFORMING TO |
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131 | These functions are GNU extensions. |
132 | Functions with similar names exist on some other systems, | |
133 | though typically with different calling signatures. | |
134 | .SH EXAMPLE | |
135 | The program below uses | |
136 | .BR getservbyport_r () | |
137 | to retrieve the service record for the port and protocol named | |
138 | in its first command-line argument. | |
139 | If a third (integer) command-line argument is supplied, | |
140 | it is used as the initial value for | |
141 | .IR buflen ; | |
142 | if | |
143 | .BR getservbyport_r () | |
144 | fails with the error | |
145 | .BR ERANGE , | |
146 | the program retries with larger buffer sizes. | |
147 | The following shell session shows a couple of sample runs: | |
148 | .in +4n | |
149 | .nf | |
150 | ||
b43a3b30 | 151 | .RB "$" " ./a.out 7 tcp 1" |
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152 | ERANGE! Retrying with larger buffer |
153 | getservbyport_r() returned: 0 (success) (buflen=87) | |
154 | s_name=echo; s_proto=tcp; s_port=7; aliases= | |
b43a3b30 | 155 | .RB "$" " ./a.out 77777 tcp" |
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156 | getservbyport_r() returned: 0 (success) (buflen=1024) |
157 | Call failed/record not found | |
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158 | .fi |
159 | .in | |
9c330504 | 160 | .SS Program source |
d84d0300 | 161 | \& |
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162 | .nf |
163 | #define _GNU_SOURCE | |
164 | #include <ctype.h> | |
165 | #include <netdb.h> | |
166 | #include <stdlib.h> | |
167 | #include <stdio.h> | |
168 | #include <errno.h> | |
169 | #include <string.h> | |
170 | ||
171 | #define MAX_BUF 10000 | |
172 | ||
173 | int | |
174 | main(int argc, char *argv[]) | |
175 | { | |
176 | int buflen, erange_cnt, port, s; | |
177 | struct servent result_buf; | |
178 | struct servent *result; | |
179 | char buf[MAX_BUF]; | |
180 | char *protop; | |
181 | char **p; | |
182 | ||
183 | if (argc < 3) { | |
72da9ef1 | 184 | printf("Usage: %s port\-num proto\-name [buflen]\\n", argv[0]); |
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185 | exit(EXIT_FAILURE); |
186 | } | |
187 | ||
188 | port = htons(atoi(argv[1])); | |
189 | protop = (strcmp(argv[2], "null") == 0 || | |
190 | strcmp(argv[2], "NULL") == 0) ? NULL : argv[2]; | |
191 | ||
192 | buflen = 1024; | |
193 | if (argc > 3) | |
194 | buflen = atoi(argv[3]); | |
195 | ||
196 | if (buflen > MAX_BUF) { | |
197 | printf("Exceeded buffer limit (%d)\\n", MAX_BUF); | |
198 | exit(EXIT_FAILURE); | |
199 | } | |
200 | ||
201 | erange_cnt = 0; | |
202 | do { | |
203 | s = getservbyport_r(port, protop, &result_buf, | |
204 | buf, buflen, &result); | |
205 | if (s == ERANGE) { | |
206 | if (erange_cnt == 0) | |
207 | printf("ERANGE! Retrying with larger buffer\\n"); | |
208 | erange_cnt++; | |
209 | ||
210 | /* Increment a byte at a time so we can see exactly | |
211 | what size buffer was required */ | |
212 | ||
213 | buflen++; | |
214 | ||
215 | if (buflen > MAX_BUF) { | |
216 | printf("Exceeded buffer limit (%d)\\n", MAX_BUF); | |
217 | exit(EXIT_FAILURE); | |
218 | } | |
219 | } | |
220 | } while (s == ERANGE); | |
221 | ||
222 | printf("getservbyport_r() returned: %s (buflen=%d)\\n", | |
223 | (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" : | |
224 | strerror(s), buflen); | |
225 | ||
226 | if (s != 0 || result == NULL) { | |
227 | printf("Call failed/record not found\\n"); | |
228 | exit(EXIT_FAILURE); | |
229 | } | |
230 | ||
231 | printf("s_name=%s; s_proto=%s; s_port=%d; aliases=", | |
232 | result_buf.s_name, result_buf.s_proto, | |
233 | ntohs(result_buf.s_port)); | |
234 | for (p = result_buf.s_aliases; *p != NULL; p++) | |
235 | printf("%s ", *p); | |
236 | printf("\\n"); | |
237 | ||
238 | exit(EXIT_SUCCESS); | |
239 | } | |
240 | .fi | |
47297adb | 241 | .SH SEE ALSO |
1280fbc6 | 242 | .BR getservent (3), |
1280fbc6 | 243 | .BR services (5) |