writen.c

APUE(第二版)的随书源代码,与第一版的代码相比增加了一些章节的代码(详见第二版的说明)

#include	"ourhdr.h"

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

	ptr = vptr;	/* can't do pointer arithmetic on void* */
	nleft = n;
	while (nleft > 0) {
		if ( (nwritten = write(fd, ptr, nleft)) <= 0)
			return(nwritten);		/* error */

		nleft -= nwritten;
		ptr   += nwritten;
	}
	return(n);
}