对fork函数理解

标签：uc

头文件： #include <unistd.h>

pid_t fork (void);

1. 创建一个子进程，失败返回-1。

#include <stdio.h>
#include <unistd.h>

int main (void) {
	printf ("%u进程：我要调用fork()了...\n", getpid ());

	pid_t pid = fork ();
	if (pid == -1) {
		perror ("fork");
		return -1;
	}

	if (pid == 0) {
		printf ("%u进程：我是%u进程的子进程。\n", getpid (),
			getppid ());
		return 0;
	}

	printf ("%u进程：我是%u进程的父进程。\n", getpid (), pid);
	sleep (1);

	return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int global = 100;

int main (void) {
	int local = 200;
	char* heap = (char*)malloc (256 * sizeof (char));
	sprintf (heap, "ABC");
	printf ("父进程：%d %d %s\n", global, local, heap);
	pid_t pid = fork ();
	if (pid == -1) {
		perror ("fork");
		return -1;
	}

	if (pid == 0) {
		global++;
		local++;
		sprintf (heap, "XYZ");
		printf ("子进程：%d %d %s\n", global, local, heap);
		free (heap);

		return 0;
	}

	sleep (1);
	printf ("父进程：%d %d %s\n", global, local, heap);
	free (heap);

	return 0;
}

#include <stdio.h>
#include <unistd.h>

int main (void) {
	printf ("ABC");

	pid_t pid = fork ();
	if (pid == -1) {
		perror ("fork");
		return -1;
	}

	if (pid == 0) {
		printf ("XYZ\n");
		return 0;
	}

	sleep (1);
	printf ("\n");

	return 0;
}

#include <stdio.h>
#include <unistd.h>

int main (void) {
	printf ("父进程：");
	int a, b, c;
	scanf ("%d%d%d", &a, &b, &c);

	pid_t pid = fork ();
	if (pid == -1) {
		perror ("fork");
		return -1;
	}

	if (pid == 0) {
		scanf ("%d%d%d", &a, &b, &c);
		printf ("子进程：%d %d %d\n", a, b, c);

		return 0;
	}

	sleep (1);
	printf ("父进程：%d %d %d\n", a, b, c);

	return 0;
}

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>

int main (void) {
	int fd = open ("ftab.txt", O_RDWR | O_CREAT | O_TRUNC, 0644);
	if (fd == -1) {
		perror ("open");
		return -1;
	}

	const char* text = "Hello, World !";
	if (write (fd, text, strlen (text) * sizeof (text[0])) == -1) {
		perror ("write");
		return -1;
	}

	pid_t pid = fork ();
	if (pid == -1) {
		perror ("fork");
		return -1;
	}

	if (pid == 0) {
		if (lseek (fd, -7, SEEK_CUR) == -1) {
			perror ("lseek");
			return -1;
		}

		close (fd);
		return 0;
	}

	sleep (1);
	text = "Linux";
	if (write (fd, text, strlen (text) * sizeof (text[0])) == -1) {
		perror ("write");
		return -1;
	}
	close (fd);
	return 0;
}

对fork函数理解

标签：uc

原文地址：http://blog.csdn.net/meetings/article/details/47123359