loop.c

unix环境高级编程第二版配套源代码 unix环境高级编程第二版配套源代码

#include "apue.h"

#define	BUFFSIZE	512

static void	sig_term(int);
static volatile sig_atomic_t	sigcaught;	/* set by signal handler */

void
loop(int ptym, int ignoreeof)
{
	pid_t	child;
	int		nread;
	char	buf[BUFFSIZE];

	if ((child = fork()) < 0) {
		err_sys("fork error");
	} else if (child == 0) {	/* child copies stdin to ptym */
		for ( ; ; ) {
			if ((nread = read(STDIN_FILENO, buf, BUFFSIZE)) < 0)
				err_sys("read error from stdin");
			else if (nread == 0)
				break;		/* EOF on stdin means we're done */
			if (writen(ptym, buf, nread) != nread)
				err_sys("writen error to master pty");
		}

		/*
		 * We always terminate when we encounter an EOF on stdin,
		 * but we notify the parent only if ignoreeof is 0.
		 */
		if (ignoreeof == 0)
			kill(getppid(), SIGTERM);	/* notify parent */
		exit(0);	/* and terminate; child can't return */
	}

	/*
	 * Parent copies ptym to stdout.
	 */
	if (signal_intr(SIGTERM, sig_term) == SIG_ERR)
		err_sys("signal_intr error for SIGTERM");

	for ( ; ; ) {
		if ((nread = read(ptym, buf, BUFFSIZE)) <= 0)
			break;		/* signal caught, error, or EOF */
		if (writen(STDOUT_FILENO, buf, nread) != nread)
			err_sys("writen error to stdout");
	}

	/*
	 * There are three ways to get here: sig_term() below caught the
	 * SIGTERM from the child, we read an EOF on the pty master (which
	 * means we have to signal the child to stop), or an error.
	 */
	if (sigcaught == 0)	/* tell child if it didn't send us the signal */
		kill(child, SIGTERM);
	/*
	 * Parent returns to caller.
	 */
}

/*
 * The child sends us SIGTERM when it gets EOF on the pty slave or
 * when read() fails.  We probably interrupted the read() of ptym.
 */
static void
sig_term(int signo)
{
	sigcaught = 1;		/* just set flag and return */
}