Advanced Programming in the UNIX® Environment

ptg10805159

Appendix C Chapter 13 Solutions 929

#include <unistd.h>

#include <time.h>

#include <sys/select.h>

unsigned

sleep(unsigned seconds)

{

int n;

unsigned slept;

time_t start, end;

struct timeval tv;

tv.tv_sec = seconds;

tv.tv_usec = 0;

time(&start);

n=select(0, NULL, NULL, NULL, &tv);

if (n == 0)

return(0);

time(&end);

slept = end - start;

if (slept >= seconds)

return(0);

return(seconds - slept);

}

Figure C.13 Athread-safe implementation ofsleep

13.3 FigureC.14 shows a solution.

#include "apue.h"

int

main(void)

{

FILE *fp;

char *p;

daemonize("getlog");

p=getlogin();

fp = fopen("/tmp/getlog.out", "w");

if (fp != NULL) {

if (p == NULL)

fprintf(fp, "no login name\n");

else

fprintf(fp, "login name: %s\n", p);

}

exit(0);

}

Figure C.14 Calldaemonizeand then obtain login name