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26 .TH GETSERVENT_R 3 2017-09-15 "GNU" "Linux Programmer's Manual"
28 getservent_r, getservbyname_r, getservbyport_r \- get
29 service entry (reentrant)
34 .BI "int getservent_r(struct servent *" result_buf ", char *" buf ,
35 .BI " size_t " buflen ", struct servent **" result );
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 );
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 );
47 Feature Test Macro Requirements for glibc (see
48 .BR feature_test_macros (7)):
53 .BR getservbyname_r (),
54 .BR getservbyport_r ():
57 Glibc 2.19 and earlier:
58 _BSD_SOURCE || _SVID_SOURCE
63 .BR getservbyname_r (),
65 .BR getservbyport_r ()
66 functions are the reentrant equivalents of, respectively,
68 .BR getservbyname (3),
70 .BR getservbyport (3).
71 They differ in the way that the
73 structure is returned,
74 and in the function calling signature and return value.
75 This manual page describes just the differences from
76 the nonreentrant functions.
78 Instead of returning a pointer to a statically allocated
80 structure as the function result,
81 these functions copy the structure into the location pointed to by
86 array is used to store the string fields pointed to by the returned
89 (The nonreentrant functions allocate these strings in static storage.)
90 The size of this array is specified in
94 is too small, the call fails with the error
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;
99 .\" the nonreentrant functions use a 1024 byte buffer -- mtk.
101 If the function call successfully obtains a service record, then
109 On success, these functions return 0.
110 On error, they return one of the positive error numbers listed in errors.
112 On error, record not found
113 .RB ( getservbyname_r (),
114 .BR getservbyport_r ()),
116 .RB ( getservent_r ())
122 .RB ( getservent_r ())
123 No more records in database.
128 Try again with a larger buffer
132 For an explanation of the terms used in this section, see
139 Interface Attribute Value
142 .BR getservbyname_r (),
143 .BR getservbyport_r ()
144 T} Thread safety MT-Safe locale
148 These functions are GNU extensions.
149 Functions with similar names exist on some other systems,
150 though typically with different calling signatures.
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
160 .BR getservbyport_r ()
163 the program retries with larger buffer sizes.
164 The following shell session shows a couple of sample runs:
168 .RB "$" " ./a.out 7 tcp 1"
169 ERANGE! Retrying with larger buffer
170 getservbyport_r() returned: 0 (success) (buflen=87)
171 s_name=echo; s_proto=tcp; s_port=7; aliases=
172 .RB "$" " ./a.out 77777 tcp"
173 getservbyport_r() returned: 0 (success) (buflen=1024)
174 Call failed/record not found
188 #define MAX_BUF 10000
191 main(int argc, char *argv[])
193 int buflen, erange_cnt, port, s;
194 struct servent result_buf;
195 struct servent *result;
201 printf("Usage: %s port\-num proto\-name [buflen]\\n", argv[0]);
205 port = htons(atoi(argv[1]));
206 protop = (strcmp(argv[2], "null") == 0 ||
207 strcmp(argv[2], "NULL") == 0) ? NULL : argv[2];
211 buflen = atoi(argv[3]);
213 if (buflen > MAX_BUF) {
214 printf("Exceeded buffer limit (%d)\\n", MAX_BUF);
220 s = getservbyport_r(port, protop, &result_buf,
221 buf, buflen, &result);
224 printf("ERANGE! Retrying with larger buffer\\n");
227 /* Increment a byte at a time so we can see exactly
228 what size buffer was required */
232 if (buflen > MAX_BUF) {
233 printf("Exceeded buffer limit (%d)\\n", MAX_BUF);
237 } while (s == ERANGE);
239 printf("getservbyport_r() returned: %s (buflen=%d)\\n",
240 (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
241 strerror(s), buflen);
243 if (s != 0 || result == NULL) {
244 printf("Call failed/record not found\\n");
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++)