#include "apue.h"#include <sys/wait.h>#define	PAGER	"${PAGER:-more}" /* environment variable, or default */intmain(int argc, char *argv[]){	char	line[MAXLINE];	FILE	*fpin, *fpout;	if (argc != 2)		err_quit("usage: a.out <pathname>");	if ((fpin = fopen(argv[1], "r")) == NULL)		err_sys("can't open %s", argv[1]);	if ((fpout = popen(PAGER, "w")) == NULL)		err_sys("popen error");	/* copy argv[1] to pager */	while (fgets(line, MAXLINE, fpin) != NULL) {		if (fputs(line, fpout) == EOF)			err_sys("fputs error to pipe");	}	if (ferror(fpin))		err_sys("fgets error");	if (pclose(fpout) == -1)		err_sys("pclose error");	exit(0);}