常用的Linux系统函数

文件I/O

open 打开文件

creat 创建文件  等同于open(const char * pathname, (O_CREAT|O_WRONLY|O_TRUNC))

close 关闭文件

write 写文件

read 读文件

lseek 移动文件的读写位置

fcntl 文件描述符操作：改变一个已打开的文件的属性

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>

int main()
{
	int fd, len;
	char s[] = "Linux\n", buffer[23];
	fd = open("/tmp/temp", O_WRONLY | O_CREAT | O_TRUNC);
	printf("%d\n", (int)sizeof(s));
	len = write(fd, s, strlen(s));
	printf("%d\n", len);
	close(fd);
	fd = open("/tmp/temp", O_RDONLY);
	len = read(fd, buffer, sizeof(buffer));
	close(fd);
	write(STDOUT_FILENO, buffer, len);
	printf("%d\n", len);
	return 0;
}

网络socket

socket 建立一个socket通信

bind 服务端绑定socket到端口

listen 服务端等待连接

accept 接受socket连接请求

connect 客户端连接服务器

/* server.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>

#define MAXLINE 80
#define SERV_PORT 8000

int main(void)
{
	struct sockaddr_in servaddr, cliaddr;
	socklen_t cliaddr_len;
	int listenfd, connfd;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
	int i, n;
	
	listenfd = socket(AF_INET, SOCK_STREAM, 0);
	
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
	
	bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
	
	listen(listenfd, 20);
	
	printf("Accepting connections ...\n");
	while (1)
	{
		cliaddr_len = sizeof(cliaddr);
		
		connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
		
		n = read(connfd, buf, MAXLINE);
		
		printf("received from %s at PORT %d\n",
			inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
			ntohs(cliaddr.sin_port));
			
		for (i = 0; i < n; i++)
			buf[i] = toupper(buf[i]);
		
		write(connfd, buf, n);
		
		close(connfd);
	}
}

/* client.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define MAXLINE 80
#define SERV_PORT 8000

int main(int argc, char *argv[])
{
	struct sockaddr_in servaddr;
	char buf[MAXLINE];
	int sockfd, n;
	char *str;
	
	if (argc != 2)
	{
		fputs("usage: ./client message\n", stderr);
		exit(1);
	}
	
	str = argv[1];
	
	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);
	
	connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
	
	write(sockfd, str, strlen(str));
	
	n = read(sockfd, buf, MAXLINE);
	
	printf("Response from server:\n");
	
	write(STDOUT_FILENO, buf, n);
	
	close(sockfd);
	
	return 0;
}

 

进程原语

 

fork 创建一个新进程

getpid 获取进程id

getppid 获取父进程id

exec族 执行函数

wait 等待子进程终止并清理子进程PCB

waitpid 等待指定子进程终止并清理子进程PCB

进程间通信

管道：pipe 创建管道

FIFO有名管道：mkfifo 创建有名管道

共享内存：

mmap方式 ：mmap 建立内存映射

System V共享内存：

shmget 获取共享内存 

shmat 连接共享内存

shmctl 控制共享内存

shmdt 拆卸共享内存

线程原语

pthread_create创建线程

pthread_self获取调用线程tid
pthread_exit线程退出函数
pthread_join用该函数的线程将挂起等待，直到id为thread的线程终止

pthread_cancel在进程内某个线程可以取消另一个线程
pthread_detach线程也可以被置为detach状态，这样的线程一旦终止就立刻回收
它占用的所有资源，而不保留终止状态。
pthread_equal比较两个线程是否相等

线程同步

互斥量pthread_mutex_t、pthread_mutex_init、pthread_mutex_destroy、pthread_mutex_lock、pthread_mutex_trylock、pthread_mutex_unlock
读写锁pthread_rwlock_t、pthread_rwlock_init、pthread_rwlock_destroy、pthread_rwlock_rdlock、pthread_rwlock_wrlock、pthread_rwlock_tryrdlock、pthread_rwlock_trywrlock、pthread_rwlock_unlock
条件变量pthread_cond_t、pthread_cond_init、pthread_cond_destroy、pthread_cond_wait、pthread_cond_timedwait、pthread_cond_signal、pthread_cond_broadcast
信号量sem_t、sem_init、sem_wait、sem_trywait、sem_timedwait、sem_post、sem_destroy