linxu c 函数使用实例
文件可以根据其存放数据的作用的不同，将其分为普通文件、目录文件、链接文件、设备文件和管道文件
1. vfork
/*
* File: main.c
* Author: root
*
* Created on 2013年11月1日, 上午9:34
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
/*
*
*/
int gvar=2;
int main(int argc, char** argv) {
pid_t pid;
int var=5;
printf("process id:%ld\n",(long)getpid());
if((pid=vfork())<0)
{
perror("error!");
return 1;
}else if(pid==0)
{
gvar--;
var++;
printf("the child process id:%ld\n gvar=%d var =%d \n",(long)getpid(),gvar,var);
_exit(0);
}else{
printf("the parent process id:%ld \n gvar=%d var=%d \n",(long)getpid(),gvar,var);
return 0;
}
return (EXIT_SUCCESS);
}
2.share memory
#include<stdio.h>
#include<string.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/ipc.h>
#include<sys/shm.h>
int main()
{
int shmid;
int proj_id;
key_t key;
int size;
char *addr;
pid_t pid;
key=IPC_PRIVATE;
//创建共享内存
shmid=shmget(key,1024,IPC_CREAT|0660);
if(shmid==-1)
{
perror("create share memory failed!");
return 1;
}
//挂载
addr=(char*)shmat(shmid,NULL,0);
if(addr==(char *)(-1))
{
perror("cannot attach!");
return 1;
}
printf("share memory segment's address:%x\n",addr);
//拷贝数据到共享内存
strcpy(addr,"welcome to mrsoft!");
//创建子进程
pid=fork();
if(pid==-1)
{
perror("error!!!!");
return 1;
}
else if(pid==0)
{ //子进程
printf("child process string is' %s'\n",addr);
_exit(0);
}
else
{
wait(NULL);
printf("parent process string is '%s'\n",addr);
//释放共享内存，反挂载
if(shmdt(addr)==-1)
{
perror("release failed!");
return 1;
}
//共享内存控制操作
if(shmctl(shmid,IPC_RMID,NULL)==-1)
{
perror("failed!");
return 1;
}
}
return 0;
}
3. TestSize
/*
* File: main.c
* Author: root
*
* Created on 2013年11月13日, 下午3:07
*/
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <stdint.h>
int main(int argc, char** argv) {
printf("CHAR_BIT is %d \n",CHAR_BIT);
printf("sizeof(char) is %d \n",sizeof(char));
printf("sizeof(short) is %d \n",sizeof(short));
printf("sizeof(int) is %d \n",sizeof(int));
printf("sizeof(long) is %d \n",sizeof(long));
printf("sizeof(long long) is %d \n\n",sizeof(long long));
// 8 1 2 4 4 8
printf("sizeof(int8_t) is %d \n",sizeof(int8_t));
printf("sizeof(int16_t) is %d \n",sizeof(int16_t));
printf("sizeof(int32_t) is %d \n",sizeof(int32_t));
printf("sizeof(int64_t) is %d \n\n",sizeof(int64_t));
// 1 2 4 8
printf("sizeof(uint8_t) is %d \n",sizeof(uint8_t));
printf("sizeof(uint16_t) is %d \n",sizeof(uint16_t));
printf("sizeof(uint32_t) is %d \n",sizeof(uint32_t));
printf("sizeof(uint64_t) is %d \n",sizeof(uint64_t));
//1 2 4 8
return (EXIT_SUCCESS);
}
4. getMac
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <string.h>
int main(int argc, char *argv[])
{
struct ifreq ifreq;
int sock;
if(argc!=2)
{
printf("Usage : ethname\n");
return 1;
}
if((sock=socket(AF_INET,SOCK_STREAM,0))<0)
{
perror("socket");
return 2;
}
strcpy(ifreq.ifr_name,argv[1]);
if(ioctl(sock,SIOCGIFHWADDR,&ifreq)<0)
{
perror("ioctl error");
return 3;
}
printf("%02x:%02x:%02x:%02x:%02x:%02x\n",
(unsigned char)ifreq.ifr_hwaddr.sa_data[0],
(unsigned char)ifreq.ifr_hwaddr.sa_data[1],
(unsigned char)ifreq.ifr_hwaddr.sa_data[2],
(unsigned char)ifreq.ifr_hwaddr.sa_data[3],
(unsigned char)ifreq.ifr_hwaddr.sa_data[4],
(unsigned char)ifreq.ifr_hwaddr.sa_data[5]);
close(sock);
return 0;
}
5.pthread
/*
* File: main.c
* Author: root
*
* Created on 2013年11月13日, 下午5:25
*/
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
pthread_t ptid;
void printtid(const char* s)
{
pid_t pid;
pthread_t tid;
pid=getpid();
tid=pthread_self();
printf("%s pid=%u tid=%u (0x%x)\n",s,(unsigned int )pid,(unsigned int )tid,(unsigned int )tid);
}
void *thr_fn(void *arg)
{
printtid("new thread:");
return (void *)0;
}
int main(int argc, char** argv) {
int err;
err=pthread_create(&ptid,NULL,thr_fn,NULL);
if(err!=0)
{
printf("can't create thread:%s\n",strerror(err));
return -1;
}
printtid("main thread:");
sleep(1);
return (EXIT_SUCCESS);
}