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包含几个用不同方式（共享内存、socket、FIFO、消息队列等）实现进程通信的小程序

//实现管道双向传送的例子    
  
  
#include    <STDIO.H>   
#include    <UNISTD.H>   
#include    <DIRENT.H>   
#include    <LIMITS.H>   
  
#define     bufflen     1024   
  
void server(), client();  
  
typedef int pid_t;  
  
int main(int argc, char **grav)  
{  
    int   n, pipe1[2], pipe2[2];  
    pid_t childpid;  
      
    if (pipe(pipe1) < 0)  
        printf("pipe error\n");  
    if (pipe(pipe2) < 0)  
        printf("pipe error\n");  
  
    if ( (childpid = fork()) < 0)  
        exit(0);  
    if (childpid > 0) {  
        close(pipe1[0]);  
        close(pipe2[1]);  
        client(pipe2[0], pipe1[1]);  
        waitpid(childpid, NULL, 0);  
        exit(0);  
    }  
    else {  
        close(pipe1[1]);  
        close(pipe2[0]);  
        server(pipe1[0], pipe2[1]);  
        exit(0);  
    }  
}  
  
//-----------------------------------------------------------------------------   
  
void server(int readfd, int writefd)  
{  
    ssize_t     n;  
    char        buff[bufflen], *ptr;  
    struct dirent    *dirp;  
    DIR         *dp;  
  
    if ( ( n = read(readfd, buff, bufflen) ) == 0)  /*read dirname form IPC channel*/  
        exit(0);  
    buff[n] = '\0'; /* null terminate */  
    ptr = buff + n;  
    if ((dp = opendir(buff)) == NULL)  
        snprintf(ptr, sizeof(buff) - n, ": not find.\n");   /* tell client error */  
    else {  
        while ( ( dirp = readdir(dp) ) != NULL) {  
            if (strcmp(dirp->d_name, ".") == 0 ||   
                strcmp(dirp->d_name, "..") == 0) /* ignore . and .. directory */  
                continue;  
            strcpy(ptr, dirp->d_name);   /* copy the filename list to the pipe */  
            n = strlen(dirp->d_name);  
            ptr += n;  
            *ptr = ' ';  
            ptr++;  
        }  
        *ptr = '\0';    /* null terminate */  
    }  
    n = strlen(buff);  
    if ( ( write(writefd, buff, n) ) != n)  
        exit(0);  
    closedir(dp);  
}  
  
//-----------------------------------------------------------------------------   
  
void client(int readfd, int writefd)  
{  
    size_t  len;  
    ssize_t n;  
    char      buff[bufflen];  
  
    fgets(buff, bufflen, stdin);        /* read pathname from the standard input */  
    len = strlen(buff);  
        /* 删除路径名结尾处的回车符 */  
if (buff[len-1] == '\n')  
        len--;  
    if ( ( write(writefd, buff, len) ) != len)  
        exit(0);  
        /* 循环从管道中读，直到读到内容为止 */  
    while ( (n = read(readfd, buff, bufflen) ) > 0)  
        if ( ( write(STDOUT_FILENO, buff, n) ) != n)  
            exit(0);  
    printf("\n");  
}