I'm currently studying IPC, I have a first program
A: Do an exec for B and wait
B: Receive through a fifo a string from a third program "C" and have to resend it to A
I was thinking to open a pipe in A before the exec, then passing fd[1] to B as an argument
if(pipe(fd)==-1){
perror("Pipe Failed");
myExit(EXIT_FAILURE);
}
close(fd[1]);
sprintf(fdString,"%d",fd[1]);
.......
if((int)(pid=fork())>0)
waiting(status);
else if(pid==0){
close(fd[0]);
execl("./B","B",fdString,(char*)0);
perror("Exec failed");
myExit(EXIT_FAILURE);
}
Then in B:
int fd=atoi(argv[1]);
//Receive string from C
len=strlen(string)+1;
if(write(fd,&len,sizeof(int))==-1){
perror("Error on writing length");
exit(EXIT_FAILURE);
}
if(write(fd,&string,len)==-1){
perror("Error on writing string");
exit(EXIT_FAILURE);
}
My problem now is reading this string in A. I was thinking to send a SIGUSR1 to A as soon as the string is written by B on the pipe and having in A something like:
signal(SIGUSR1, signalHandler);
........
static void signalHandler(int signo){
switch(signo){
case SIGUSR1:
listen();
break;
default: break;
}
}
........
static void listen(){
int len;
if(read(fd[0],&len,sizeof(int))<sizeof(int)){
perror("Error reading len");
myExit(EXIT_FAILURE);
}
char string[len];
if(read(fd[0],string,len)<len){
perror("Error reading string");
myExit(EXIT_FAILURE);
}
printf("String: %s with length %d\n", string, len);
}
However what I get is "Error reading len: Success" , what's wrong ?
Sorry if my English is bad, any help is appreciated, thanks!