rtime(3) Library Functions Manual rtime(3)NAME
rtime - get remote time
SYNOPSIS
#include <sys/types.h>
#include <sys/time.h>
#include <netinet/in.h>
int rtime(addrp, timep, timeout)
struct sockaddr_in *addrp;
struct timeval *timep;
struct timeval *timeout;
DESCRIPTION
The rtime() function consults the Internet Time Server at the address pointed to by addrp and returns the remote time in the timeval struct
pointed to by timep. Normally, the UDP protocol is used when consulting the Time Server. The timeout parameter specifies how long the rou-
tine should wait before giving up when waiting for a reply. If timeout is specified as NULL, however, the routine will instead use TCP and
block until a reply is received from the time server.
The routine returns 0 if it is successful. Otherwise, it returns -1 and errno is set to reflect the cause of the error.
RELATED INFORMATION timed(8), timedc(8) delim off
rtime(3)
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RTIME(3) Linux Programmer's Manual RTIME(3)NAME
rtime - get time from a remote machine
SYNOPSIS
#include <rpc/des_crypt.h>
int rtime(struct sockaddr_in *addrp, struct rpc_timeval *timep,
struct rpc_timeval *timeout);
DESCRIPTION
This function uses the Time Server Protocol as described in RFC 868 to obtain the time from a remote machine.
The Time Server Protocol gives the time in seconds since 00:00:00 UTC, 1 Jan 1900, and this function subtracts the appropriate constant in
order to convert the result to seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
When timeout is non-NULL, the udp/time socket (port 37) is used. Otherwise, the tcp/time socket (port 37) is used.
RETURN VALUE
On success, 0 is returned, and the obtained 32-bit time value is stored in timep->tv_sec. In case of error -1 is returned, and errno is
set appropriately.
ERRORS
All errors for underlying functions (sendto(2), poll(2), recvfrom(2), connect(2), read(2)) can occur. Moreover:
EIO The number of returned bytes is not 4.
ETIMEDOUT
The waiting time as defined in timeout has expired.
NOTES
Only IPv4 is supported.
Some in.timed versions only support TCP. Try the example program with use_tcp set to 1.
Libc5 uses the prototype
int rtime(struct sockaddr_in *, struct timeval *, struct timeval *);
and requires <sys/time.h> instead of <rpc/auth_des.h>.
BUGS
rtime() in glibc 2.2.5 and earlier does not work properly on 64-bit machines.
EXAMPLE
This example requires that port 37 is up and open. You may check that the time entry within /etc/inetd.conf is not commented out.
The program connects to a computer called "linux". Using "localhost" does not work. The result is the localtime of the computer "linux".
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <rpc/auth_des.h>
#include <netdb.h>
int use_tcp = 0;
char *servername = "linux";
int
main(void)
{
struct sockaddr_in name;
struct rpc_timeval time1 = {0,0};
struct rpc_timeval timeout = {1,0};
struct hostent *hent;
int ret;
memset((char *) &name, 0, sizeof(name));
sethostent(1);
hent = gethostbyname(servername);
memcpy((char *) &name.sin_addr, hent->h_addr, hent->h_length);
ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
if (ret < 0)
perror("rtime error");
else
printf("%s
", ctime((time_t *) &time1.tv_sec));
exit(EXIT_SUCCESS);
}
SEE ALSO ntpdate(1), inetd(8)COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2010-02-25 RTIME(3)