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Linux系统编程代码汇总

2026-09-06 20:29:41

一.程序进程线程概念_进程ID号

#include<sys/types.h>#include<unistd.h>#include<stdio.h>intmain(void){pid_t pid;while(1)	{printf("pid = %d\n", getpid()); //当前进程id号printf("ppid = %d\n", getppid());//当前进程父进程id号printf("Hello world\n");sleep(1);	}return 0;}

运行结果：

 pstree -p

可以查看我们的进程树，就是进程关系

systemd(init): 所有进程的父进程

二.消息队列

#include<stdio.h>#include<sys/ipc.h>#include<sys/shm.h>#include<sys/types.h>#include<unistd.h>#include<string.h>#include<sys/wait.h>#include<sys/msg.h>#define MY_TYPE  9527intmain(void){int msgid;pid_t pid;struct msgbuf	{long mtype;char mtext[100];int number;	};struct msgbuf buff;	msgid = msgget(IPC_PRIVATE, 0666 | IPC_EXCL); /* 不晓得为什么必须加上0666才可以*/if (msgid == -1) {	    perror("msgget");	    return -1;	}	pid = fork();if(pid > 0)	{	    sleep(1);		buff.mtype = MY_TYPE;printf("Please enter a string you want to send:\n");gets(buff.mtext);printf("Please enter a nubmer you want to send:\n");scanf("%d", &buff.number);msgsnd(msgid, &buff, sizeof(buff) - sizeof(buff.mtype), 0);waitpid(pid, NULL, 0);	}else if(pid == 0)	{printf("Child process is waiting for msg:\n");msgrcv(msgid, &buff, sizeof(buff) - sizeof(buff.mtype), MY_TYPE, 0);printf("Child process read from msg: %s, %d\n", buff.mtext, buff.number);	}elseperror("fork");return 0;}

运行效果：

用消息队队列让不同进程之间通信

接收部分代码

#include<stdio.h>#include<sys/ipc.h>#include<sys/shm.h>#include<sys/types.h>#include<unistd.h>#include<string.h>#include<sys/wait.h>#include<sys/msg.h>#define MY_TYPE  9527#define MY_KEY	 1314intmain(void){int msgid;struct msgbuf	{long mtype;char mtext[100];int number;	};struct msgbuf buff;	msgid = msgget(MY_KEY, IPC_CREAT|0644);while(1)	{printf("Process is waiting for msg:\n");msgrcv(msgid, &buff, sizeof(buff) - sizeof(buff.mtype), MY_TYPE, 0);printf("Process read from msg: %s, %d\n", buff.mtext, buff.number);	}msgctl(msgid, IPC_RMID, NULL);return 0;}

发送部分代码

#include<stdio.h>#include<sys/ipc.h>#include<sys/shm.h>#include<sys/types.h>#include<unistd.h>#include<string.h>#include<sys/wait.h>#include<sys/msg.h>#define MY_TYPE  9527#define MY_KEY	 1314intmain(void){int msgid;struct msgbuf	{long mtype;char mtext[100];int number;	};struct msgbuf buff;	msgid = msgget(MY_KEY, IPC_CREAT); //ftok	buff.mtype = MY_TYPE;printf("Please enter a string you want to send:\n");gets(buff.mtext);printf("Please enter a nubmer you want to send:\n");scanf("%d", &buff.number);msgsnd(msgid, &buff, sizeof(buff) - sizeof(buff.mtype), 0);return 0;}

运行效果

遇到的问题，一开始是没有用root 权限运行，导致接收消息的时候出现了死循环，但是后面发现用root权限运行之后，可以正常接收消息，但是后面再运行，发现我要发三次后，才能收到第四次的消息，试了几次都是这样，不清楚为什么。

用命令ipcs看了一下

--------- 消息队列 -----------键        msqid      拥有者  权限     已用字节数 消息      0x00000522 0          root       0          0            0

是这样的，怎么重新编译程序都不行，后面重新启动了虚拟机，发现程序是root权限的。我重新编译了一下，就可以了。

用命令ipcs重新看了一下，发现拥有者和权限那里已经变了。

三.共享内存

#include<stdio.h>#include<sys/ipc.h>#include<sys/shm.h>#include<sys/types.h>#include<unistd.h>#include<string.h>#include<sys/wait.h>char msg[] = "Hello world";intmain(void){int shmid;pid_t pid;	shmid = shmget(IPC_PRIVATE, 1024, IPC_CREAT);	pid = fork();if(pid > 0)	{char *p_addr;		p_addr = shmat(shmid, NULL, 0);memset(p_addr, '\0', sizeof(msg));memcpy(p_addr, msg, sizeof(msg));shmdt(p_addr);waitpid(pid, NULL, 0);	}else if(pid == 0)	{char *c_addr;		c_addr = shmat(shmid, NULL, 0);printf("Child process waits a short time: \n");sleep(3);printf("Child Process reads from shared memory: %s\n", c_addr);shmdt(c_addr);	}elseperror("fork");return 0;}

运行效果：

一个进程写共享内存，另外一个进程读共享内存

write

#include<stdio.h>#include<sys/ipc.h>#include<sys/shm.h>#include<sys/types.h>#include<unistd.h>#include<string.h>#include<sys/wait.h>char msg[] = "Hello world";#define MY_KEY	9527intmain(void){int shmid;	shmid = shmget(MY_KEY, 1024, IPC_CREAT);char *p_addr;	p_addr = shmat(shmid, NULL, 0);memset(p_addr, '\0', sizeof(msg));memcpy(p_addr, msg, sizeof(msg));shmdt(p_addr);//	shmctl(shmid, IPC_RMID, NULL);return 0;}

read

#include<stdio.h>#include<sys/ipc.h>#include<sys/shm.h>#include<sys/types.h>#include<unistd.h>#include<string.h>#include<sys/wait.h>#define MY_KEY	9527intmain(void){int shmid;	shmid = shmget(MY_KEY, 1024, IPC_CREAT);char *c_addr;	c_addr = shmat(shmid, NULL, 0);printf("Read from shared memory: %s\n", c_addr);shmdt(c_addr);return 0;}

运行效果:

先write

再read

四.互斥锁

用在线程中

pthread_mutex_init 初始化互斥锁
pthread_mutex_lock(&mutex) 上锁
要做的事情
pthread_mutex_unlock(&mutex) 解锁

#include<pthread.h>#include<stdio.h>#include<unistd.h>#include<stdlib.h>#include<semaphore.h>void *thread1_function(void *arg);void *thread2_function(void *arg);pthread_mutex_t mutex;intmain(void){pthread_t pthread1, pthread2;int ret;pthread_mutex_init(&mutex, NULL);	ret = pthread_create(&pthread1, NULL, thread1_function, NULL);if(ret != 0)	{perror("pthread_create");exit(1);	}	ret = pthread_create(&pthread2, NULL, thread2_function, NULL);if(ret != 0)	{perror("pthread_create");exit(1);	}pthread_join(pthread1, NULL);pthread_join(pthread2, NULL);printf("The thread is over, process is over too.\n");return 0;}void *thread1_function(void *arg){int i;while(1)	{pthread_mutex_lock(&mutex);for(i = 0; i < 10; i++)		{printf("Hello world\n");sleep(1);		}pthread_mutex_unlock(&mutex);sleep(1);	}return NULL;}void *thread2_function(void *arg){int i;sleep(1);while(1)	{pthread_mutex_lock(&mutex);for(i = 0; i < 10; i++)		{printf("Good moring\n");sleep(1);		}pthread_mutex_unlock(&mutex);sleep(1);	}return NULL;}