Hi All, Anyone know how to call the UNIX command "date" from C?

[christheprogrammer]

Hi All,
Anyone know how to call the UNIX command "date" from C? I just want to print out the date using C. Thanks
Chris [sig][/sig]

 

[rbobbitt]

This will produce output similar to Unix date with no arguments. You can, of course, print it out however you like, look into the standard time libraries.

#include <stdio.h>
#include <time.h>
int main(void)
{
struct tm *p;
long tmm;
char *wk_days[] = { &quot;Sun&quot;,&quot;Mon&quot;,&quot;Tue&quot;,&quot;Wed&quot;,&quot;Thu&quot;,&quot;Fri&quot;,&quot;Sat&quot; };
char *mo_days[] = { &quot;Jan&quot;,&quot;Feb&quot;,&quot;Mar&quot;,&quot;Apr&quot;,&quot;May&quot;,&quot;Jun&quot;,&quot;Jul&quot;,
&quot;Aug&quot;,&quot;Sep&quot;,&quot;Oct&quot;,&quot;Nov&quot;,&quot;Dec&quot; };
time(&tmm);
if ((p=localtime(&tmm))!=NULL) {
printf(&quot;%s %s %2d %2.2d:%2.2d:%2.2d %s %d\n&quot;,wk_days[p->tm_wday],
mo_days[p->tm_mon],
p->tm_mday,
p->tm_hour,
p->tm_min,
p->tm_sec,
tzname[1],
p->tm_year+1900);
}
return 0;

}

Regards [sig]<p>Russ<br><a href=mailto:bobbitts@hotmail.com>bobbitts@hotmail.com</a><br><a href=

http://home.earthlink.net/~bobbitts>Bobbitt

is in</a><br>[/sig]

 

[shail]

hi chris,

rbobbitt 's method is the right way to do it. one should avoid using system (&quot;date&quot; in code. but that is the way to call command line prog in a C program.

int main { exit(system(&quot;date&quot);}

will do the trick...

-afaik,
shail

[sig][/sig]

 

[rbobbitt]

Right, if you _really_ want to call the 'date' program, you can use system(). The reason you want to avoid this generally is that your code is less portable as you're making assumptions about the implementation and, for that matter, the existence of the program you're calling.

For instance, if I run shail's example on my win98 system, I'm also prompted to change the date.

Whoops, forgot the ()'s in main

int main() { exit(system(&quot;date&quot);}

[sig]<p>Russ<br><a href=mailto:bobbitts@hotmail.com>bobbitts@hotmail.com</a><br><a href=

http://home.earthlink.net/~bobbitts>Bobbitt

is in</a><br>[/sig]

 

[christheprogrammer]

Thanks Guys,
I actually solved the problem this way:

#include <time.h>

void current_time()
{
time_t time_struct;
char *time_now;

time(&time_struct);
time_now = ctime(&time_struct);
while (*time_now != '\0')
{
if (*time_now != '\n')
printf(&quot;%c&quot;,*time_now);
time_now++;
}

printf(&quot;\n&quot;
} [sig][/sig]

 

[shail]

hi chris,

if u have the while loop only to print up to the end of string and if block to not print the new line character... then simply change time_now[24] = '0'; or whatever u want.
and print (&quot;%s&quot;, time_now);

ctime returns a 26 byte string ending with \n\0 no problems with using %s directly on it. ofcourse don't forget to free(time_now) memory... u will need another var. to store the base pointer.

-shail [sig][/sig]