1 .\" Copyright 2008, Linux Foundation, written by Michael Kerrisk
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24 .TH GETSERVENT_R 3 2010-09-10 "GNU" "Linux Programmer's Manual"
26 getservent_r, getservbyname_r, getservbyport_r \- get
27 service entry (reentrant)
32 .BI "int getservent_r(struct servent *" result_buf ", char *" buf ,
33 .BI " size_t " buflen ", struct servent **" result );
35 .BI "int getservbyname_r(const char *" name ", const char *" proto ,
36 .BI " struct servent *" result_buf ", char *" buf ,
37 .BI " size_t " buflen ", struct servent **" result );
39 .BI "int getservbyport_r(int " port ", const char *" proto ,
40 .BI " struct servent *" result_buf ", char *" buf ,
41 .BI " size_t " buflen ", struct servent **" result );
45 Feature Test Macro Requirements for glibc (see
46 .BR feature_test_macros (7)):
51 .BR getservbyname_r (),
52 .BR getservbyport_r ():
54 _BSD_SOURCE || _SVID_SOURCE
60 .BR getservbyname_r (),
62 .BR getservbyport_r ()
63 functions are the reentrant equivalents of, respectively,
65 .BR getservbyname (3),
67 .BR getservbyport (3).
68 They differ in the way that the
70 structure is returned,
71 and in the function calling signature and return value.
72 This manual page describes just the differences from
73 the nonreentrant functions.
75 Instead of returning a pointer to a statically allocated
77 structure as the function result,
78 these functions copy the structure into the location pointed to by
83 array is used to store the string fields pointed to by the returned
86 (The nonreentrant functions allocate these strings in static storage.)
87 The size of this array is specified in
91 is too small, the call fails with the error
93 and the caller must try again with a larger buffer.
94 (A buffer of length 1024 bytes should be sufficient for most applications.)
95 .\" I can find no information on the required/recommended buffer size;
96 .\" the nonreentrant functions use a 1024 byte buffer -- mtk.
98 If the function call successfully obtains a service record, then
106 On success, these functions return 0.
107 On error, they return one of the positive error numbers listed in errors.
109 On error, record not found
110 .RB ( getservbyname_r (),
111 .BR getservbyport_r ()),
113 .RB ( getservent_r ())
119 .RB ( getservent_r ())
120 No more records in database.
125 Try again with a larger buffer
129 These functions are GNU extensions.
130 Functions with similar names exist on some other systems,
131 though typically with different calling signatures.
133 The program below uses
134 .BR getservbyport_r ()
135 to retrieve the service record for the port and protocol named
136 in its first command-line argument.
137 If a third (integer) command-line argument is supplied,
138 it is used as the initial value for
141 .BR getservbyport_r ()
144 the program retries with larger buffer sizes.
145 The following shell session shows a couple of sample runs:
149 .RB "$" " ./a.out 7 tcp 1"
150 ERANGE! Retrying with larger buffer
151 getservbyport_r() returned: 0 (success) (buflen=87)
152 s_name=echo; s_proto=tcp; s_port=7; aliases=
153 .RB "$" " ./a.out 77777 tcp"
154 getservbyport_r() returned: 0 (success) (buflen=1024)
155 Call failed/record not found
169 #define MAX_BUF 10000
172 main(int argc, char *argv[])
174 int buflen, erange_cnt, port, s;
175 struct servent result_buf;
176 struct servent *result;
182 printf("Usage: %s port\-num proto-name [buflen]\\n", argv[0]);
186 port = htons(atoi(argv[1]));
187 protop = (strcmp(argv[2], "null") == 0 ||
188 strcmp(argv[2], "NULL") == 0) ? NULL : argv[2];
192 buflen = atoi(argv[3]);
194 if (buflen > MAX_BUF) {
195 printf("Exceeded buffer limit (%d)\\n", MAX_BUF);
201 s = getservbyport_r(port, protop, &result_buf,
202 buf, buflen, &result);
205 printf("ERANGE! Retrying with larger buffer\\n");
208 /* Increment a byte at a time so we can see exactly
209 what size buffer was required */
213 if (buflen > MAX_BUF) {
214 printf("Exceeded buffer limit (%d)\\n", MAX_BUF);
218 } while (s == ERANGE);
220 printf("getservbyport_r() returned: %s (buflen=%d)\\n",
221 (s == 0) ? "0 (success)" : (s == ENOENT) ? "ENOENT" :
222 strerror(s), buflen);
224 if (s != 0 || result == NULL) {
225 printf("Call failed/record not found\\n");
229 printf("s_name=%s; s_proto=%s; s_port=%d; aliases=",
230 result_buf.s_name, result_buf.s_proto,
231 ntohs(result_buf.s_port));
232 for (p = result_buf.s_aliases; *p != NULL; p++)