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Diffstat (limited to 'man3/rtime.3')
| -rw-r--r-- | man3/rtime.3 | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/man3/rtime.3 b/man3/rtime.3 new file mode 100644 index 0000000..a866d0b --- /dev/null +++ b/man3/rtime.3 @@ -0,0 +1,153 @@ +'\" t +.\" Copyright 2003 walter harms (walter.harms@informatik.uni-oldenburg.de) +.\" +.\" SPDX-License-Identifier: GPL-1.0-or-later +.\" +.\" Modified 2003-04-04 Walter Harms +.\" <walter.harms@informatik.uni-oldenburg.de> +.\" +.\" Slightly polished, aeb, 2003-04-06 +.\" +.TH rtime 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +rtime \- get time from a remote machine +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B "#include <rpc/auth_des.h>" +.PP +.BI "int rtime(struct sockaddr_in *" addrp ", struct rpc_timeval *" timep , +.BI " struct rpc_timeval *" timeout ); +.fi +.SH DESCRIPTION +This function uses the Time Server Protocol as described in +RFC\ 868 to obtain the time from a remote machine. +.PP +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). +.PP +When +.I timeout +is non-NULL, the udp/time socket (port 37) is used. +Otherwise, the tcp/time socket (port 37) is used. +.SH RETURN VALUE +On success, 0 is returned, and the obtained 32-bit time value is stored in +.IR timep\->tv_sec . +In case of error \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +All errors for underlying functions +.RB ( sendto (2), +.BR poll (2), +.BR recvfrom (2), +.BR connect (2), +.BR read (2)) +can occur. +Moreover: +.TP +.B EIO +The number of returned bytes is not 4. +.TP +.B ETIMEDOUT +The waiting time as defined in timeout has expired. +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR rtime () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH NOTES +Only IPv4 is supported. +.PP +Some +.I in.timed +versions support only TCP. +Try the example program with +.I use_tcp +set to 1. +.\" .PP +.\" Libc5 uses the prototype +.\" .PP +.\" .nf +.\" int rtime(struct sockaddr_in *, struct timeval *, struct timeval *); +.\" .fi +.\" .PP +.\" and requires +.\" .I <sys/time.h> +.\" instead of +.\" .IR <rpc/auth_des.h> . +.SH BUGS +.BR rtime () +in glibc 2.2.5 and earlier does not work properly on 64-bit machines. +.SH EXAMPLES +This example requires that port 37 is up and open. +You may check +that the time entry within +.I /etc/inetd.conf +is not commented out. +.PP +The program connects to a computer called "linux". +Using "localhost" does not work. +The result is the localtime of the computer "linux". +.PP +.\" SRC BEGIN (rtime.c) +.EX +#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\en", ctime(&t)); + } +\& + exit(EXIT_SUCCESS); +} +.EE +.\" SRC END +.SH SEE ALSO +.\" .BR netdate (1), +.BR ntpdate (1), +.\" .BR rdate (1), +.BR inetd (8) |