rtime(3) - f39

1rtime(3)                   Library Functions Manual                   rtime(3)
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NAME

6       rtime - get time from a remote machine
7

LIBRARY

9       Standard C library (libc, -lc)
10

SYNOPSIS

12       #include <rpc/auth_des.h>
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14       int rtime(struct sockaddr_in *addrp, struct rpc_timeval *timep,
15                 struct rpc_timeval *timeout);
16

DESCRIPTION

18       This  function uses the Time Server Protocol as described in RFC 868 to
19       obtain the time from a remote machine.
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21       The Time Server Protocol gives the time in seconds since 00:00:00  UTC,
22       1 Jan 1900, and this function subtracts the appropriate constant in or‐
23       der to convert the  result  to  seconds  since  the  Epoch,  1970-01-01
24       00:00:00 +0000 (UTC).
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26       When  timeout is non-NULL, the udp/time socket (port 37) is used.  Oth‐
27       erwise, the tcp/time socket (port 37) is used.
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RETURN VALUE

30       On success, 0 is returned, and the obtained 32-bit time value is stored
31       in timep->tv_sec.  In case of error -1 is returned, and errno is set to
32       indicate the error.
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ERRORS

35       All errors for underlying functions (sendto(2),  poll(2),  recvfrom(2),
36       connect(2), read(2)) can occur.  Moreover:
37
38       EIO    The number of returned bytes is not 4.
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40       ETIMEDOUT
41              The waiting time as defined in timeout has expired.
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ATTRIBUTES

44       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
45       tributes(7).
46
47       ┌────────────────────────────────────────────┬───────────────┬─────────┐
48       │Interface                                   │ Attribute     │ Value   │
49       ├────────────────────────────────────────────┼───────────────┼─────────┤
50       │rtime()                                     │ Thread safety │ MT-Safe │
51       └────────────────────────────────────────────┴───────────────┴─────────┘
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NOTES

54       Only IPv4 is supported.
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56       Some in.timed versions support only TCP.  Try the example program  with
57       use_tcp set to 1.
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BUGS

60       rtime()  in  glibc  2.2.5  and earlier does not work properly on 64-bit
61       machines.
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EXAMPLES

64       This example requires that port 37 is up and open.  You may check  that
65       the time entry within /etc/inetd.conf is not commented out.
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67       The  program  connects to a computer called "linux".  Using "localhost"
68       does not work.  The result is the localtime of the computer "linux".
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70       #include <errno.h>
71       #include <netdb.h>
72       #include <stdio.h>
73       #include <stdlib.h>
74       #include <string.h>
75       #include <time.h>
76
77       #include <rpc/auth_des.h>
78
79       static int use_tcp = 0;
80       static const char servername[] = "linux";
81
82       int
83       main(void)
84       {
85           int                 ret;
86           time_t              t;
87           struct hostent      *hent;
88           struct rpc_timeval  time1 = {0, 0};
89           struct rpc_timeval  timeout = {1, 0};
90           struct sockaddr_in  name;
91
92           memset(&name, 0, sizeof(name));
93           sethostent(1);
94           hent = gethostbyname(servername);
95           memcpy(&name.sin_addr, hent->h_addr, hent->h_length);
96
97           ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
98           if (ret < 0)
99               perror("rtime error");
100           else {
101               t = time1.tv_sec;
102               printf("%s\n", ctime(&t));
103           }
104
105           exit(EXIT_SUCCESS);
106       }
107