Print int from signal handler using write or async-safe functions

Question

I want to print a number into log or to a terminal using write (or any async-safe function) inside a signal handler. I would prefer not to use buffered I/O.

Answer 1

If you insist on using xprintf() inside a signal handler you can always roll your own version that does not rely on buffered I/O:

#include  /* vsnprintf() */

void myprintf(FILE *fp, char *fmt, ...)
{
char buff[512];
int rc,fd;
va_list argh;
va_start (argh, fmt);

rc = vsnprintf(buff, sizeof buff, fmt, argh);
if (rc < 0  || rc >= sizeof buff) {
        rc = sprintf(buff, "Argh!: %d:\n", rc);
        }

if (!fp) fp = stderr;
fd = fileno(fp);
if (fd < 0) return;
if (rc > 0)  write(fd, buff, rc);
return;
}