I want to put the output of GNU/Linux date command in a character array.
Example:
char array[25];
$ date
Thu Jul 19 09:21:31 IST 2012
printf("%s", array);
/* Should display "Thu Jul 19 09:21:31 IST 2012" */
I tried this:
#include <stdio.h>
#include <string.h>
#define SIZE 50
int main()
{
char array[SIZE];
sprintf(array, "%s", system("date"));
printf("\nGot this: %s\n", array);
return 0;
}
But the output shows NULL in the array.
Use popen to be able to read the output of a command. Make sure to close the stream with pclose.
FILE *f = popen("date", "r");
fgets(array, sizeof(array), f);
pclose(f);
But, you could use localtime and strftime instead of executing an external program.
time_t t = time(0);
struct tm lt;
localtime_r(&t, <);
strftime(array, sizeof(array), "%a %b %d &T %z %Y", <);
ctime is similar, but does not include the timezone.
ctime_r(&t, array);
When you call system(command), its return value is not a char* to the command's output, but an exit code of the command. The command completes successfully, and returns 0; that's why you see a NULL. If you would like to fetch the string returned by the "date" command, you need to capture the output stream and convert it to a string.
#include <stdio.h>
#include <time.h>
int main(void)
{
time_t result;
char array[25] = {'\0'};
result = time(NULL);
sprintf(array, "%s", asctime(localtime(&result)));
printf("%s", array);
return(0);
}
