Linux.com

rtime.3

RTIME

Section: Linux Programmer's Manual (3)
Updated: 2008-07-12
Index Return to Main Contents
 

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 00:00:00 UTC, 1 Jan 1970, the Unix Epoch.

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\n", ctime((time_t *) &time1.tv_sec));

    exit(EXIT_SUCCESS);
}
 

SEE ALSO

ntpdate(1), inetd(8)  

COLOPHON

This page is part of release 3.21 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
NOTES
BUGS
EXAMPLE
SEE ALSO
COLOPHON

 

Comments

Subscribe to Comments Feed

Upcoming Linux Foundation Courses

  1. LFD331 Developing Linux Device Drivers
    25 Aug » 29 Aug - Virtual
    Details
  2. LFD411 Embedded Linux Development
    25 Aug » 29 Aug - Santa Clara, CA
    Details
  3. LFS422 High Availability Linux Architecture
    08 Sep » 11 Sep - Raleigh, NC
    Details

View All Upcoming Courses

Become an Individual Member
Check out the Friday Funnies

Sign Up For the Linux.com Newsletter


Who we are ?

The Linux Foundation is a non-profit consortium dedicated to the growth of Linux.

More About the foundation...

Frequent Questions

Join / Linux Training / Board