sigdemo3.c

understanding unix/linux programming source code(bruce molay)

/* sigdemo3.c
 *	purpose:   show answers to signal questions
 *	question1: does the handler stay in effect after a signal arrives?
 *	question2: what if a signalX arrives while handling signalX?
 *      question3: what if a signalX arrives while handling signalY?
 *      question4: what happens to read() when a signal arrives?
 */

#include	<stdio.h>
#include	<signal.h>

#define	INPUTLEN	100

main(int ac, char *av[])
{
	void	inthandler(int);
	void	quithandler(int);
	char	input[INPUTLEN];
	int	nchars;

	signal( SIGINT,  inthandler );		/* set handler */
	signal( SIGQUIT, quithandler );		/* set handler */

	do {
		printf("\nType a message\n");
		nchars = read(0, input, (INPUTLEN-1));
		if ( nchars == -1 )
			perror("read returned an error");
		else {
			input[nchars] = '\0';
			printf("You typed: %s", input);
		}
	} 
	while( strncmp( input , "quit" , 4 ) != 0 );
}

void inthandler(int s)
{
	printf(" Received signal %d .. waiting\n", s );
	sleep(2);
	printf("  Leaving inthandler \n");
}

void quithandler(int s)
{
	printf(" Received signal %d .. waiting\n", s );
	sleep(3);
	printf("  Leaving quithandler \n");
}