convert human date to epoch

[Tim Nelson]

I see an number of references in here of using C to convert a supplied argument from epoch to a human date but how about human date to epoch ? Looks like the ctime source should do it but I just can't seem to get it ..

Below is the source for the epoch to human. Could someone elaborate for the reverse ?

#include
int main(argc, argv)
int argc;
char **argv;
{
time_t t=strtoul(argv[1], NULL, 0);
printf("%s", ctime(&t));
}

[A. Clay Stephenson · Accepted solution]

Hi Tim:

The function you are looking for is 'mktime'.

I've attached a small example program that first gets the current time, displays it's epoch seconds and Year,Month,Day,Hr,Min, and Second. It then adds 1 to to day and calls mktime to get a new epoch seconds 1 day (86400 seconds later).

That should be good enough to get you started.

By the way, the stuff is really easy to do in both directions in Perl.

[Mike Hassell]

Tim,

The GNU date command supports output of epoch, which I find to be rather useful if you need to convert the current time/date stamp to epoch. Of course this only helps if you're trying to convert the current time/date stamp, rather than a supplied human date -> epoch.

You can download a precompiled version of GNU date here:

http://hpux.connect.org.uk/hppd/hpux/Gnu/sh_utils-2.0/

syntax:

date +%s

Hope that helps.

-Mike

[Craig Rants]

Also, the perl option

/usr/contrib/bin/perl -e "print time"

GL,
C

[Tim Nelson]

Thanks again to all.. THe below seems to work the best.
#include
#include
#include
#include
#include

#define FALSE 0
#define TRUE 1

int main(argc,argv)
int argc;
char *argv[];

{
struct tm *dateptr;
time_t date;
int do_exit=FALSE;

if (argc != 2) {
fprintf(stderr, "Usage: %s \n", argv[0]);
exit(1);
}


/* Convert date */
dateptr = getdate(argv[1]);
if (getdate_err != 0) {
fprintf(stderr, "%s: Could not interpret %s. Error = %d\n", argv[0], argv[1], getdate_err);
exit(1);
}

date = mktime(dateptr);
if (date == -1) {
fprintf(stderr, "Could not \"mktime\" for date, errno=%d\n", errno);
exit(1);
}

printf("%d\n", date);

exit(0);
}