writen.c

UNIX环境高级编程源代码源代码,适合初学linux者

#include "apue.h"

ssize_t             /* Write "n" bytes to a descriptor  */
writen(int fd, const void *ptr, size_t n)
{
	size_t		nleft;
	ssize_t		nwritten;

	nleft = n;
	while (nleft > 0) {
		if ((nwritten = write(fd, ptr, nleft)) < 0) {
			if (nleft == n)
				return(-1); /* error, return -1 */
			else
				break;      /* error, return amount written so far */
		} else if (nwritten == 0) {
			break;
		}
		nleft -= nwritten;
		ptr   += nwritten;
	}
	return(n - nleft);      /* return >= 0 */
}