进程间通信，管道 实现 TELL_WAIT、TELL_PARENT、TELL_CHILD、WAIT_PARENT、WAIT_CHILD

#include "apue.h"

 

static int pfd1[2],pfd2[2];

 

void TELL_WAIT(void){

if(pipe(pfd1)<0 || pipe(pfd2)<0)

err_sys("pipe error");

}

 

void TELL_PARENT(pid_t pid){

if(write(pfd2[1],"c",1)!=1)

err_sys("write error");

}

 

void WAIT_PARENT(void){

char c;

if(read(pfd1[0],&c,1)!=1)

err_sys("read error");

if(c!='p')

err_quit("WAIT_PARENT:incorrect data");

}

 

void TELL_CHILD(pid_t pid){

if(write(pfd1[1],"p",1)!=1)

err_sys("write error");

}

 

void WAIT_CHILD(void)

{char c;

if(read(pfd2[0],&c,1)!=1)

err_sys("read_error");

if(c!='c')

err_quit("WAIT_CHILD:incorrect data");

}