linux-C-共享内存+信号量-一进程写文件,另一进程读输入
deepfuture@deepfuture-laptop:~/private/mytest$ gcc -std=gnu99 -o testshm testshm.c
testshm.c: In function ‘main’:
testshm.c:38: warning: implicit declaration of function ‘semget’
testshm.c:41: warning: implicit declaration of function ‘exit’
testshm.c:41: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:45: warning: implicit declaration of function ‘semctl’
testshm.c:48: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:51: warning: implicit declaration of function ‘shmget’
testshm.c:54: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:57: warning: implicit declaration of function ‘shmat’
testshm.c:60: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:63: warning: implicit declaration of function ‘memset’
testshm.c:63: warning: incompatible implicit declaration of built-in function ‘memset’
testshm.c:69: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:78: warning: implicit declaration of function ‘strlen’
testshm.c:78: warning: incompatible implicit declaration of built-in function ‘strlen’
testshm.c:85: warning: implicit declaration of function ‘memcpy’
testshm.c:85: warning: incompatible implicit declaration of built-in function ‘memcpy’
testshm.c:92: warning: implicit declaration of function ‘semop’
testshm.c:95: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:119: warning: incompatible implicit declaration of built-in function ‘strlen’
testshm.c:124: warning: incompatible implicit declaration of built-in function ‘exit’
testshm.c:132: warning: implicit declaration of function ‘wait’
testshm.c:134: warning: implicit declaration of function ‘shmdt’
testshm.c:139: warning: implicit declaration of function ‘shmctl’
testshm.c:142: warning: incompatible implicit declaration of built-in function ‘exit’
deepfuture@deepfuture-laptop:~/private/mytest$ ./testshm
deepfuture.javeye.com#line 1$deepfuture
deepfuture.javeye.com#line 2$javaeye
deepfuture.javeye.com#line 3$com
deepfuture.javeye.com#line 4$deepfuture.iteye.com
deepfuture.javeye.com#line 5$Q
deepfuture.javeye.com#line 6$
退出....
deepfuture@deepfuture-laptop:~/private/mytest$ cat abc.txt
deepfuture
javaeye
com
deepfuture.iteye.com
deepfuture@deepfuture-laptop:~/private/mytest$
#include <stdio.h>
#include <unistd.h>
#include <linux/types.h>
#include <linux/shm.h>
#include <linux/sem.h>
#include <linux/ipc.h>
#define MAXS (1024+1)
#define BUFFERSIZE 200
#define SEMID 251//信号标志
#define FILENAME "abc.txt"
#define SHMKEY 241//共享内存标志
#define SHMSIZE MAXS//共享内存大小
//程序完成父进程接收键盘输入，子进程存入文件FILENAME。
//deepfuture.iteye.com
int main(void){
char strbuf[MAXS];
char buf[BUFFERSIZE];
int sem_id;
int shm_id;
int pid;
int rc,res;
struct sembuf sem_op;//信号集结构
union semun sem_val;//信号量数值
char *cur;
FILE *myfile;
char *shm_addr;
int line=1;
//建立信号量集，其中只有一个信号量 deepfuture.iteye.com
sem_id=semget(SEMID,1,IPC_CREAT|0600);//SEMID为为正整数，则为公共的；1为信号集的数量；
if (sem_id==-1){
printf("create sem error!\n");
exit(1);
}
//信号量初始化
sem_val.val=0;
rc=semctl(sem_id,0,SETVAL,sem_val);//设置信号量
if (rc==-1){
printf("initlize sem error!\n");
exit(1);
}
//建立共享内存
shm_id=shmget(SHMKEY,SHMSIZE,IPC_CREAT|0600);//参数为:标志，大小，权限
if (shm_id==-1){
printf("create shm error!\n");
exit(1);
}
//attach共享内存。连接共享内存 deepfuture.iteye.com
shm_addr=(char *)shmat(shm_id,NULL,0);//返回共享内存地址 deepfuture.iteye.com
if (!shm_addr){
printf("shmat error!\n");
exit(1);
}
//初始化数据
memset(shm_addr,'\0',MAXS);
cur=shm_addr;//当前字符起始地址
//创建进程
pid=fork();
if (pid==-1){
printf("fork error!\n");
exit(1);
}
else if(pid==0){//子进程，接受键盘输入，往共享内存中写字符行 deepfuture.iteye.com
int isend=0;//是否结束输入
printf("\ndeepfuture.javeye.com#line %d$",line); //自定义键盘输入时使用的SHELL外观
while((!isend)&&fgets(buf,BUFFERSIZE,stdin)!=NULL){//从shell中读入一行
line++;
printf("\ndeepfuture.javeye.com#line %d$",line); //自定义键盘输入时使用的SHELL外观
if (buf[0]=='Q'&&strlen(buf)<=2){//单个字符Q表示退出输入
isend++;//退出输入
printf("\n退出....\n");
}
else
{//如果不是退出命令
//写共享内存 deepfuture.iteye.com
memcpy(cur,buf,strlen(buf));
cur+=strlen(buf);
}
//写入一行，增加信号
sem_op.sem_num=0;
sem_op.sem_op=1;
sem_op.sem_flg=0;
semop(sem_id,&sem_op,1);//操作信号量，每次+1
}
*cur=-1;
exit(0);
}
else{//父进程，从共享内存中读字符行 ,并写入文件 deepfuture.iteye.com
while(1)
{
//读出一行，减少信号 deepfuture.iteye.com
sem_op.sem_num=0;
sem_op.sem_op=-1;
sem_op.sem_flg=0;
semop(sem_id,&sem_op,1);//操作信号量，每次-1
//deepfuture.iteye.com 读共享内存中一行
if ((*cur)==-1) break;//输入结束
int i;
for (i=0;*cur!='\n';cur++,i++){
buf[i]=*cur;
}
cur++;
buf[i]='\n';
buf[++i]=0;
//写文件
FILE *fp=fopen(FILENAME,"ab");
res=fwrite(buf,strlen(buf),1,fp);//deepfuture.iteye.com 写入一个行，长度为strlen(buf)，个数为1
//size_t fwrite(const void * ptr,size_t size,size_t nmemb,FILE * stream);
//size为要写入的每个数据的大小(多少字节)，nmemb为要写入数据的个数。deepfuture.iteye.com
if (res==-1){
perror("write error on pipe\n");
exit(1);
}
fclose(fp);
}
wait(&pid);//等待子进程结束，即用户输入完毕
//分离共享进程
if (shmdt(shm_addr)==-1){
printf("shmdt error!\n");
}
//撤销共享内存,任何进程只要有权限，都可以撤销共享内存，不一定非要创建它的进程
struct shmid_ds shm_desc;
if (shmctl(shm_id,IPC_RMID,&shm_desc)==-1){
printf("shmctl error!\n");
}
exit(0);
}
}