---
name: "rtime"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/rtime"
---

# rtime(3)

get time from a remote machine

## NAME

rtime - get time from a remote machine

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <rpc/auth_des.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 to indicate the error.

## ERRORS

All errors for underlying functions ([**sendto**(2)](/sendto/2.md), [**poll**(2)](/poll/2.md), [**recvfrom**(2)](/recvfrom/2.md), [**connect**(2)](/connect/2.md), [**read**(2)](/read/2.md)) can occur. Moreover:

- **EIO**

  The number of returned bytes is not 4.

- **ETIMEDOUT**

  The waiting time as defined in timeout has expired.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **rtime**() | Thread safety | MT-Safe |

## NOTES

Only IPv4 is supported.

Some *in.timed* versions support only TCP. Try the example program with *use\_tcp* set to 1.

## BUGS

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

## EXAMPLES

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 <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <rpc/auth_des.h>
static int use_tcp = 0;
static const char servername[] = "linux";
int
main(void)
{
    int                 ret;
    time_t              t;
    struct hostent      *hent;
    struct rpc_timeval  time1 = {0, 0};
    struct rpc_timeval  timeout = {1, 0};
    struct sockaddr_in  name;
    memset(&name, 0, sizeof(name));
    sethostent(1);
    hent = gethostbyname(servername);
    memcpy(&name.sin_addr, hent->h_addr, hent->h_length);
    ret = rtime(&name, &time1, use_tcp ? NULL : &timeout);
    if (ret < 0)
        perror("rtime error");
    else {
        t = time1.tv_sec;
        printf("%s\n", ctime(&t));
    }
    exit(EXIT_SUCCESS);
}
```

## SEE ALSO

[**ntpdate**(1)](/ntpdate/1.md), [**inetd**(8)](/inetd/8.md)