Simple time program won't show time

[dellthinker]

Is there any reason this code snippet won't do what it's supposed to do?

I'm learning socket programming and there's a simple program that tells the time but I think MSVC isn't building this code because of deprecated code.

#include <stdio.h>
#include <time.h>


int main() {
	time_t timer;
	time(&timer);
	char buf[26];

	printf_s("Local time is: %d", ctime_s(buf,sizeof(buf), &timer));
	return 0;
}

When I run this code all I get is this....

Local time is: 0

How do i get this to show the time from my computer?

[salem_c]

https://en.cppreference.com/w/c/chrono/ctime
ctime_s returns an error code, not a string.

Maybe something like

if ( ctime_s(buf,sizeof(buf), &timer) == 0 ) {
    printf_s("Local time is: %s", buf);
}

[Philip Nicoletti]

The return value of ctime_s is of type errno_t not a string

    errno_t err = ctime_s(buf, sizeof(buf), &timer);

    if (err == 0)
        printf_s("Local time is: %s", buf);

[ovidiucucu]

As already said before, ctime_s function returns 0 (zero) in case of success. So it's no wonder what your program prints. Modify it as follows:

#include <stdio.h>
#include <time.h>

int main() 
{
	time_t timer;
	time(&timer);
	char buf[26];

	ctime_s(buf, sizeof(buf), &timer);
	printf_s("Local time is: %s", buf);	
	return 0;
}

Additional note:
ctime returns a pointer to static data and is not thread-safe. In addition, it modifies the static tm object which may be shared with gmtime and localtime. POSIX marks this function obsolete and recommends strftime instead. The C standard also recommends strftime, which is safer and more flexible.

#include <stdio.h>
#include <time.h>

int main() 
{
    time_t timer = { 0 };
    time(&timer);
    char buf[26] = { '\0' };

    struct tm localTime = { 0 };
    localtime_s(&localTime, &timer);
    strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", &localTime);
    printf_s("Local time is: %s\n", buf);

    return 0;
}

See also:

• ctime, ctime_s
• strftime, wcsftime, _strftime_l, _wcsftime_l
• localtime_s, _localtime32_s, _localtime64_s