waitdemo2.c

unix linux 编程实践源代码

/* waitdemo2.c - shows how parent gets child status
 */

#include	<stdio.h>

#define	DELAY	5

main()
{
	int  newpid;
	void child_code(), parent_code();

	printf("before: mypid is %d\n", getpid());

	if ( (newpid = fork()) == -1 )
		perror("fork");
	else if ( newpid == 0 )
		child_code(DELAY);
	else
		parent_code(newpid);
}
/*
 * new process takes a nap and then exits
 */
void child_code(int delay)
{
	printf("child %d here. will sleep for %d seconds\n", getpid(), delay);
	sleep(delay);
	printf("child done. about to exit\n");
	exit(17);
}
/*
 * parent waits for child then prints a message
 */
void parent_code(int childpid)
{
	int wait_rv;		/* return value from wait() */
	int child_status;
	int high_8, low_7, bit_7;

	wait_rv = wait(&child_status);
	printf("done waiting for %d. Wait returned: %d\n", childpid, wait_rv);

	high_8 = child_status >> 8;     /* 1111 1111 0000 0000 */
	low_7  = child_status & 0x7F;   /* 0000 0000 0111 1111 */
	bit_7  = child_status & 0x80;   /* 0000 0000 1000 0000 */
	printf("status: exit=%d, sig=%d, core=%d\n", high_8, low_7, bit_7);
}